944 Transmission Walkthrough (image heavy)
 

Well i have been meaning to put this together for some time. Here is a general walk through of our 944 Transmissions. This one in Particular is a 944 turbo trans, We are setting it up to receive a 944 S2 crown wheel and pinion and an aftermarket Modena LSD. Obviously without the right tools its going to make things a bit difficult, but not impossible.

So we step into the tear down

Step 1.
set the Gearbox up so that it can be worked on
Attachment 1208268
Step 2
Lock the CV flange with a screw driver and remove the 6mm allen bolts
Attachment 1208269
Step 3
With a screw driver puncture the rear seal and pry it out
Attachment 1208270
Step 4
Remove the 17mm gear selector detent
Attachment 1208271
Step 5
Remove the 3 10mm socket bolts, remove the gear selector plate
Attachment 1208272
http://i718.photobucket.com/albums/w...%20trans/5.jpg
Step 6.Lock the input shaft and select a gear. THis will help lock the Pinion so that you can remove the triple square bolt Behind the Rear seal. Remove the triple square bolt.
Attachment 1208273
http://i718.photobucket.com/albums/w...anslock001.jpg
Attachment 1208274
Step 7
Now remove all the 6mm allen bolts holding on the rear housing. then tap the rear housing off with a drift. alternate sides with the drift until the housing is removed
http://i718.photobucket.com/albums/w...%20trans/6.jpg
Step 8
Remove the 17mm bolt on 5th gear
Attachment 1208275
Step 9
Use a puller to remove the rear bearing race and part of the 5th gear assembly.
http://i718.photobucket.com/albums/w...%20trans/9.jpg
Step 10
Remove the circlip in the 5th gear assembly
Attachment 1208276
Step 11.
Next remove the 5th gear selector fork dowel with a punch.
http://i718.photobucket.com/albums/w...20trans/11.jpg
Step 12.
With a bit of coercing you can now remove 5th gear.
Attachment 1208277
Step 13.
Use a 2 arm puller to remove the matched 5th gear. It is easier if you heat the gear up with hot air guns before removal
Attachment 1208278
Step 14
Remove the shim for 5th gear. you can see it below sitting atop the main shaft bearing.
Step 15
Remove the 2 6mm stop bolts and the 17mm stop bolts and detents on the main carrier case
Attachment 1208279
step 16
Now remove all of the 13mm bolts holding the main carrier to the diff carrier. Use a drift and tap both sides of the main carrier until it is loose from the diff housing. you can now remove the main carrier with the gearset.
Attachment 1208280
Step 17
with a punch remove the dowel for 1st/2nd and for 3rd/4th.
http://i718.photobucket.com/albums/w...20trans/18.jpg
Step 18
you can now remove 3rd/4th selector Rod. be careful though as there is a small locking detent which lives in the 3rd/4th selector Rod. when removing you will most likely hear it fall into the main carrier case. you will also find a detent and spring beneath the 3rd/4th selector rod
Attachment 1208281
Attachment 1208282
Attachment 1208283
Step 19
Remove selector Rod Locks with a magnet
Attachment 1208284
Attachment 1208285
Step 20
You can now move the pinion forward with 1st/2nd selector rod and now remove the input shaft
Attachment 1208286
Attachment 1208287
Attachment 1208288
step 21
With the pinion removed you can now disassemble it if needed. You will need a press for this. you can see where the circlips are.
Attachment 1208289
Step 22
Here is the Pinion assembled with new bearings ready to have the pinion preload set. Every time the bearings are replaced the preload will need to be rechecked and modified if necessary. Next photo is of the tools needed to assemble the 944 trans and set pinion preload, pinion depth and diff backlash
Attachment 1208290
http://i718.photobucket.com/albums/w...20trans/37.jpg
Step 23.
Setting preload. We use the original shims behind the bearing shells to first check pinion preload. remove old bearing shells and replace with the new ones.
Attachment 1208291
Attachment 1208292
Step 24
With the Pinion in place and main carrier torqued to the diff case(all bolts) you can now check Pinion preload with a torque gauge as shown. you turn the torque gauge until the Pinion is turning and then take the reading. We use 2.5NM as a good preload. Assemble the shims so that 2.5nm is reached. This may take a few attempts with different shims
http://i718.photobucket.com/albums/w...20trans/38.jpg
Attachment 1208293
Attachment 1208294

Step 25
Next up is pinion depth.
The RO distance for the 944 S2 crownwheel and pinion is 59.65mm. to this we add the "quite running" number on the new crown wheel. In our case you can see here is 0.36mm.
Attachment 1208230
Step 26
Here you can see us setting the pinion depth tool to our desired level. In our case the number was 60.01mm. We set the dial gauge at 2.5mm depth with the micrometer attached
Attachment 1208231
Step 27
The pinion is in place and torqued. The Pinion also has a special tool(flat magnet) attached to it. This is so we can use the pinion depth tool against it and get an accurate reading.
The tool in placed where the diff would be placed and the diff case torque down. We now turn the tool until we read a maximum depth. We are trying to get as close to Zero as possible on the gauge.(which is our original 60.01 reading) Usually we get it within .01 of our desired quiet running distance. Remember when obtaining the Quiet running distance you will be moving the pinion forward or backwards. Considering the pinion preload is already set you need to remember if you remove shims from one side of the pinion to move it in a certain direction you must then add the exact same thickness shim(s) to the other side to keep your preload correct. Attachment 1208232
Attachment 1208233
Step 28
Assemble the diff with new bearings.(and in our case a new crown wheel and pinion, always use new crown wheel bolts) Its best to heat the Bearing with heat guns to aid in installation.
Attachment 1208234
Step 29
Setting diff preload
you can now remove the Pinion again. And set the preload as you did with the Pinion. Using shims behind the new diff side shells Install the Diff and you can now set the diff preload to 2.5NM.
Attachment 1208235
Step 30
Setting Diff backlash.
When setting diff backlash we are looking to obtain .10mm of movement on our dial gauge. this is a very small amount of movement so a dial gauge is needed. This is done with the Pinion torqued onto the diff housing with the main case(but without the gearset). The backlash tool is moved side to side to see the freeplay on the dial gauge. this will take some trial and error to get right.
Attachment 1208236
Step 31
Time to re assessable the transmission. basic reverse of our disassemble. but a few things to look out for.
Make sure the pin(short arrow) is in the slot (big arrow) for reverse gear. other wise you will have problems.
Attachment 1208237
Step 32
assemble Pinion with 1st/2nd selector shaft.
Attachment 1208238
Step 33
Place locks in place and detent underneath 3rd/4th selector rod. Make sure the small lock is in place before 3rd/4th selector rod is installed. i use grease to hold it in place
Attachment 1208239
Attachment 1208240
Attachment 1208241
Attachment 1208242
Attachment 1208243
Step 34
install Dowel for 1st/2nd and 3rd/4th selector Rods
Attachment 1208244
Step 35
install stop bolts
Attachment 1208245
Step 36
Put shims back on before 5th gear install
Attachment 1208246
Attachment 1208247
Step 37
Heat 5th gear and install.(it needs to be hot)
Attachment 1208248
Attachment 1208249
Step 38
Install 5th gear set assembly, install dowel, install circlip
Attachment 1208250
Attachment 1208251
Attachment 1208252
Step 39
Heat 5th gear syncromesh ring and install, then heat inner bearing race and install
Attachment 1208253
Attachment 1208254
Attachment 1208255
Step 40
Torque up 5th gear bolt to 70NM
Attachment 1208256
Step 41
assemble with transmission sealant on gasket and torque together
Attachment 1208257
http://i718.photobucket.com/albums/w...0trans/765.jpg
Attachment 1208258
Step 42
Heat up outer bearing race and install
Attachment 1208259
Step 43
Remove input seal from diff case
Apply transmission sealant to between main case and diff case and torque down.
Attachment 1208260
Attachment 1208261
Step 44
install reverse switch
Attachment 1208262
Step 45
install selector, install selector plate, install top detent
http://i718.photobucket.com/albums/w...20trans/81.jpg
Attachment 1208263
Attachment 1208264
Step 46
Install Rear seal, front seal and torque side flanges
http://i718.photobucket.com/albums/w...20trans/84.jpg
Attachment 1208265
Attachment 1208266
Trans build now complete
Attachment 1208267

regards
Sean

Excellent. Thanks much for that.

nice write up! :thumbup:

Thank you so much. Have been thinking about doing a aftermarket diff in my gear box, and this has given me a better understanding how the gearbox is put together and if i want to do it my self.

Great write-up! Thanks much for posting that. A few questions for you.
1. The factory manual states 0.30mm should be added to the pinion shim thickness for pre-load, and 0.50mm should be added for carrier shim thickness for pre-load. My experience shows these numbers to be too thick by about 0.15 and 0.10mm, respecitvely. Curious as to your experience?
2. Of the three transaxles I have, one of them (came from an S2) has a shim/plate between the gear housing and rear housing that is probably 8mm thick. I have never seen any references to it elsewhere. I'm curious to know if you've seen this, and if so, any info as to whey itis there? FWIW, the rear housing on that transaxle is shorter by that much. The one that has it is the only one wihtout a cooling loop.
3. Any secrets for removing the triple-square bolt from the back of the input shaft? I eventually got them, but they are bears!

Amazing writeup. What a valuable resource for everyone. THANKS!

Most excellent write up Sean!

I have been back and forth with buying a used LSD box, or installing the LSD I have on hand to my gearbox... Guess I need to start searching for the special tools... as I am sure I will use them more than once!

the tans reinforcing plate is available, my understanding is it is used to stabilize the rear of the housing when horsepower is stepped up (V8 swaps, and GT40 replica builds)..

Here is just one source I have found over the years for them.. there are others!
http://www.texasperformanceconcepts....sionparts.html

The fact you made it look that easy shows how hard it is

Excellent Write Up, I honestly Learned a great deal!

Thanks, John! Had never seen that before. Probably won't need it for my mild SP3 car, but at least I know what it is.

Post of the year! Thank you!

Fantastic. Excellent write up. Thank you for your time to do this.

Could an admin please make this a sticky of sort?

2 things
1. we need a section for this on the 951 section
2. where is testarosa badge

Very nice pictures and writeup

Great pictures!

Nice!

If only installing an LSD, would the procedure be exactly the same except taking apart the pinion for bearing change? Cause the be bearings was the reason for taking pinion apart?

Does the crown wheel and pinion sit on the LSD? And could some steps be skipped if only installing LSD?

Is this considered a complete rebuild of the transmission or would that include all gears too?

My 220 tranny is whining....what is wrong with it?

Thanks
/P

Very Very nice.

How do you save a thread to the HD. Not just a bookmark, but the entire thread?

If you just replace the "ring" portion, the carrier, the bearings, that kind of thing, the job is MUCH easier! Also note that the specs for a new rebuild are different than one that has been in service (specifically, the torque to turn is 200N-cm versus about 60 N-cm). The service manual for this is pretty good, but this post is MUCH less ambiguous.

Gears are rarely, if ever, replaced. Usually just the synchros and shaft bearings, from MY experience, but I defer to the OP on this.

Ok,

What would aprox the parts of a typical rebuild cost and where can I find the parts?
My tranny has 120k miles and whines. Would it be difficult to cure this for a DIY?

Can I service the LSD and at what cost or do I source a new one?

Hi 67King
We have found that the specs in the manual are really only suggestions. In fact in almost every rebuild we have done the shims are usually out more then that. From experience we use just the shims that were original to the box and then check the preload, modify if necessary then move onto the depth and modify if necessary. I will say we have an advantage here in that we have hundreds of shims to suit the 4 main bearings (S1, S2 and S3, S4)
I dont believe i have seen the shim you are referring to, but i may be wrong. Joka seems to be onto something there.
I should have included the trans lock we have.(i will edit the original and add it)
We have a tool that goes on the input shaft splines. that way you can lock it into a vice, select a gear(which locks the gear set) and then you can undo the triple square with a breaker bar.
Attachment 1208227
Attachment 1208228

When installing just the LSD you need to remove the main case with the gearset. But you will not need to remove the gearset from the main case as you will be working only on the diff case.

The crown wheel does bolt to the LSD. you will need to remove the bearings on the LSD to install the Crownwheel. Always use new crownwheel bolts. they are a one use wonder. You will then only have to set diff preload and diff backlash. all the other steps are there only to dismantle the gearset.

As 67King has mentioned usually you will not be replacing and gears. You would most likely replace a few Syncros and bearings. Unless you have damage to a Gear itself. Gears are matched so that you cannot just replace one side of the gear. For instance if you damaged the input shaft 5th gear then you would need to replace the Pinion 5th gear. Or else you could get whine in that gear.

If your 220 Transmissions whines then there could be multiple issues. If it whines in every gear then it is most likely from the crown wheel and pinion or a bearing associated with it. Obviously if it whines only in a particular gear(s) then the issue can be traced just to those matched gears.

You are completely correct 67King. New bearing preloads are to be set a little tighter then a used bearing. The specs i have included are for New bearings.

you know your nuts sean.

Awesome Sean,

Thank you for sharing this. I will be tearing into an extra box I have that has something wrong with second gear. I will be referring back to this when I do.

Thanks again!!

Great writeup Sean. Thanks for taking the time to do this.
Agreed that this should be in a sticky somewhere. Haven't seen much moderation in this part of the world for some time.

What would General Melchant say??

Very good writeup, the only thing that I was going to add its that you need a means of holding the input shaft still in order to break loose or torque the bolt that is on the tail end of the input shaft. But, your subsequent post shows a proper tool in order to do so. I have something similar laying around my shop, but I could not find it the last time I had my trans apart, so I put an extra clamping sleeve that I had laying around onto the input shaft (the one that normally goes there to clamp the input shaft of the transmission to the splined driveshaft of the torque tube) in a vise and was able to loosen and torque the bolt that way. Be sure that it is indeed a spare clamping sleeve, as it can easily break given the amount of torque involved!

I was using a spare driveshaft couple that I had - but I actually broke the thing! I ended up putting a monkey wrench on the round part of it after I broke it, which did work.

as per the others this is a fantastic write-up and it comes at the exact perfect time for me as I have a turbo trans getting a Guards LSD this week

Naaay!

I was just about to comment that would be a good way to hold the input shaft. Maybe it may work even better with a hex bolt installed in the sleeve and torqued up. That way the sleeve would not be able to splay.

There is not much a monkey wrench wont fix. Were you still able to torque it up when assembling?

Very good write up Sean. I just printed it out and will use it as a guide line in my future trans projects. Thank You :)

Great write-up guys. I'll keep you in mind next time I need some transmission work done.

Killer thread man, Thanks for the info, Saving this one!!

Amazing thread! Its still a big magic box to me, but I understand it a little better, thanks.

no worries guys glad we can help. Thought it about time for another tech thread.

Tool requirements/availability
 

Amazing write up - thanks!!

Couple of questions - the preload tool looks to be VERY specific to this application. I would like to try a rebuild but not sure where to find the tools that are necessary. Does anybody have any ideas on this?

Also, who sells shims?

In looking at different vendors it looks like around $850 for bearings, synchros, seals and gaskets for a complete rebuild.

Lastly, does anybody make a spool for these transmissions? Me and some buddies race and options are $1800 LSD unit or weld the spider gears. Anybody make a spool to keep this clean and cheap?

Thanks,

Ken

none of the ones I have to rebuild are ever that clean! Good thread, I've done 5 or of them now, not the worst ones to do but still a bit tricky.

Know anyone looking to sell a 385 bar etc? I have been looking for several years and have not found one available.

Thanks for the timely write up! :bowdown:
I have a spare LSD in need of rebuild...winter project.

Shims can be bought directly from Porsche. You could also ask some of the vendors like paragon or pelican about them too.

have not seen any spools for a 944 transmission.

The transmission got a wash before we took it apart. i always try and clean them first. that way it keeps the floor/workbench and tools clean

have you tried directly from Porsche or VW. Being that it has a VW part vw 385/1

Been NLA for years.

:thumbup: WOW Great Write Up!!!!!!!!!!!!!!!!!!!!

Thanks so much for this write up! A friend of mine told me about this thread and i'm lucky that Thingo knew the name of the topic, because rebuild or revision is not said in this topic..
I'll be using all of this in the near future to rebuild my S2 gearbox and probably add a LSD in it!

This is an excellent tutorial with clear instructions a great pictures.

Before I undertake such a repair, can somebody help me with something? When he says remove the bolts, is it righty-tighty / lefty-loosey or is it righty-a-way to the check book and have somebody else do this for you before you loosey your mind because this looks way out of my league.

Makes my oil changing skills look like a kindergarten finger painting versus Leonardo da Vinci's Mona Lisa.

Bump for an awesome thread....just a quick question...what is the torque value for that last bolt underneath the lid/rear seal????

Thanks!

Not a problem.

All bolts are anti clockwise to loosen and clockwise to tighten. its not terribly difficult but it could be time consuming if its your first go at it

70NM / 51 ft lb

Regards
Sean

Thank you sir!

in this write up there is a note on one of the pictures that one should make sure that the pin on the reverse gear selector rod is in the slot.

Does annyone have an idea on what kind of problems would occur if it is not?

I ask this because i'm trying to diagnose a gearbox problem

Any help would be appreciated

Hi Flipo,
If the pin is not in its correct position then the gearbox will be stuck in reverse. If you were to try select another gear the gearbox will lock up.

What is the problem you are experiencing?

Regards
Sean

Hey Sean ,thanks for the reply . the problem i experienced is the following:
in practice i shifted down to third gear but he jumped back out , i then adjusted
the schifter stick by moving it backwards slightly and after a test run the problem seemed to be fixed but 10min in the race on sunday i could only select second and fourth gear an later on only fouth gear non of the other gears could be selected .

I took the tranny appart but i can't find anything out of the ordinary ,there are no broken pieces .I just noticed that it was possibel to move the plate with the pin that is on the reverse selector rod over the plate with the slot that pivots on the bolt .I can only asume that this plate was posisioned to low so that the pin was able to jump out of the slot .but i do not know if this would explain the symptons described above???

I hope you understand any of this .

sorry for my poor English

Hi Flipo,
The problem you describe almost sounds like its related to the actual shifter mechanism itself. You have probably already done it but double check the bushes on the shift linkage on the transmission. Also check to see if you have much freeplay at the gearstick.( on the 968 they run bushes in the gearstick that can wear out).

There could be 2 reasons the transmission jumped out of gear.
1. the gear was not selected properly, meaning that if there was a lot of slop in the linkage system somewhere it may feel like it has the correct amount of throw but it may not be enough to get the gear all the way. Causing the gear to just out.
2. one or more of the gearbox detents are stuck or hard to move when in place. ( these are the bullet looking pieces with springs behind them. to check their operation put them in their original positions and push them down with a screw driver or punch to make sure they do not bind.

the fact that it would not select any other gear then 4th tells me that the gearstick linkage seems not to be getting the correct amount of movement to reach 1/2 - 4/5.

BTW is it a 5 speed or 6 speed

Regards
Sean

It's an AOR transmision, the weard thing is that the trans has been working properly for 12 to 15 races past season

I will check everything you mentioned tomorow . Thanks for the help Sean !

Attachment 701414Problem resolved , there was nothing wrong with the transmission ! It was the shift lever , I have the lindsey racing adjustable lever and both of the locking screws came out resulting the threaded ball to turn slowly turn upwards until it limited forward movement of the lever .

Well diagnosed Sean!

Thanks Patrick,
Glad you found the problem Flipo, even better it wont cost anything to fix.
Sean

Thanks for the help Sean.

Hi guys,

I'm going to rebuild my gearbox together with Flipo and placing my LSD in. I read that the standard LSD can be "upgraded" by torqueing down a bolt on the LSD a little more to get a 60% instead of 40%LSD. Does anyone have any info about this?

Thanks!

Hi Dutch944,
its actually not true that you can upgrade the standard LSD by increasing the shim thickness inside the LSD unit. All you are manipulating is the initial locking of the unit. To change the % of a LSD unit the ramps inside the unit must be changed. As far as i am aware no one manufactures alternative ramps for the standard porsche LSD, On that note the Guard Transmission LSD come with 2 locking values (as the unit can be pulled apart and the ramps be turned to set a different %)
regards
Sean

Hi Sean,

Thanks for the info. I'll just be putting the LSD in and refurbish the gearbox. Apart from a view bearings Flipo has almost all the parts we need so i'll be doing it in a view weeks. Is there anything you want me to take pictures of for the start post?

Thanks! Bas

funny i just called 944online to ask some questions and then found this. Asked him if he could put some parts together and send 'em my way. He then said that I would f*** myself and then have a box of parts he wants him to put together. I liked his honesty from his experience. I have never done this transmission, but i'm not afraid to get my hands dirty in this one. Where did you get those special tools from? Like that spline holder.

Sean: Do you have a walkthrough of only LSD install? :-)

Just bought an S2 box and hope it has the LSD but otherwise I might take the LSD from my turbo box and swap it in the S2.

Is this a direct swap and how hard is it to do this?

I've read that Audi V8 diff from late eighties fits in the 016 box if you just mill down one axle 5mm. This is a torsen diff but available cheap.

Any other things to do while doing this mod?

Thanks

Well, just the LSD install is not that hard, but if you take the Porsche manual you'll be able to do all of the work.. I did my gearbox together with Flipo, actually it was just a LSD swap but to make sure we checked all the bearing and gears!

Hi Peedster
Basically the LSD is step 29 and 30. But you still need to remove the gearset from the diff carrier. This includes removing the gear selector shaft in step 5. It s not too difficult.

Seeing that the gearset is out, just inspect some of the bearings and their shells that are visible and replace if they look worn.

Im not sure about the Audi V8 diff.

Regards
Sean

Thanks,

And the 951 diff is the same unit found in the S2 AOT?

Setting diff preload and shimming is fairly easy to I hope but do this require any special tools?

I've read that TonyG gets the diff out from the side maybe without taking the main housing away? Is this possible or does the rear housing need to come out?

/Peter

Yes same LSD, The shimming and preload can be done without the special tools, unfortunately only the 968 gearbox allows the diff to slide out without removing the gearset case. the 944 requires the case to be removed as the input shaft gets in the way.
Regards
Sean

Bumping this great post and reading it again with new perspective, because of my recent transaxle issues have to determine my next step.

Hi David,
Have you pulled the trans apart yet?
Regards
Sean

No disassemble other than draining the fluid, at this point in time after reviewing the above procedure, if I can find an S2 AOT, I will just swap it out and not repair this standard UY code as I do not have the specialized tools

Thank you Sean for such a great post. I just finished replacing the R&P in one of my spares. I wanted to try prior to having a new gearset cryo treated. So far everything seems ok running through the gears and the pattern looked good. I'm installing it tomorrow night and will report back.

The plan is to see how this goes, and if it doesn't go well, I'm going to try out the G31 box next.

It was an interesting experiment so far.

Great post indeed! Thanks. I keep meaning to save this thread for fear the pictures will be red x's by the time I try to use it. Is there a way to download/save a thread, pictures and all?

print page one to a pdf file, around 80 meg. Captures all the pictures. Great thread.

Im glad its become of some good use to you guys. We have taken a lot of info from this forum and want to give back where we can.

I would be interested to see what would become of the G31 box, I have done a few rebuilds/reseals on them and just from visualising the internals, and the cast aluminium case(not like the cast steel on the 944) i just can't see it being stronger then a 944 box, in particular the turbo gearboxes. The 968 box does certainly look the strongest in regards to the larger G50 differential (larger C&P too). Gear size wise or strength it would be on par with the 944 turbo gearbox. There is no proof in my thoughts. Happy to be proven wrong too.
Sean

A couple of tips for the 944 trans work.
1. I used an old clutch with a bar attached to hold the input shaft.
2. When assembling; set the pinion cluster in the steel case, then set the reverse idler gear.
3. The main shaft is easily installed into the steel case, without the collar for the rear bearing. Once the main shaft is set, then install the bearing collar.
4. the LSD trans will need the oil modifier to keep the LSD from chattering.

hello
 

Great post, but I am having problems with the fork with the small lock in it, it will not insert back in hole, does it need to be pressed in?

Great post, but I am having problems with the fork with the small lock in it, it will not insert back in hole, does it need to be pressed in?

Not sure where you are in the rebuild. What gear or location are you referring to?

Make sure that the 1st/2nd and 5th/reverse control rods are in their neutral position. If not, their lock-out detents will intrude into the 3rd/4th control rod's bore and keep you from inserting the control rod.

With a flashlight and a small angle pick, push back on both detents to make sure it can move out of the way of the 3rd/4th control rod.

Do *not* force it in, not necessary and will only do bad things.

Make sure the pinion shaft is reasonably centered, perhaps propping it up. You want to have everything lined up in the gear carrier to get things to move properly: pinion shaft, 1st/2nd control rod, 5th/rev control rod, etc.

And if you think this is hard, let me tell you about doing a 924 type YR gearbox...

I think I got it......hope it drives...lol

Sorry to drag this up from the dead, but I'm curious how far I'd need to dig into the trans to replace 2nd and 4th gear synchros? I would just need to take the diff out, and then take off gears 5-2? If I didn't replace any bearings (the trans is quiet in all gears, just grinds going into 2nd and 4th) would I still need to mess with setting the diff preload, ect?

Also, what could keep the car from going into Reverse easily? It's not synchronized, so I'm not sure what could be the issue. It usually takes a few tries to get the box into reverse; I usually have to go into 1st first and it grinds going into reverse half the time.

Box is an LSD 951 box, so worth it to me to rebuild as I can't afford to replace it.

The pro's may have other comments. No need to open up the differential section. And there is a synchro for reverse, but mine is like you discuss, but should not grind. Grinding would indicate the clutch is not fully disengaged. Make sure no additional carpet under the clutch pedal, from floor mats. Also, you may have some remaining air in the clutch hydraulics, as these are a pain to bleed.

I have replaced the synchros in 3 of my 944 transmissions. Not overly difficult, but you will need access to a press, and gear puller. And lay out all the parts in order removed. Go through the pictorial teardown a few times.

Alan's could be spot on there. by the sounds of it the clutch may not be completely disengaging. Unless of course you have some very worn synchros. Reverse does not have a synchro and in saying that we have seen some very worn reverse gear engagement teeth. Almost to the point they are square instead of pointy which can cause the symptoms you are having. As Alan said there is no need to remove the diff side plate just undo the gear section of the box and slide it out.
Regards
Sean

OK. Leave diff in place. Check.

I'm crystal clear on the procedure until step 22.

To replace 2nd gear synchro I'll have to disassemble the pinion shaft with a press. Ok, no problem.

After that, on step 23 is states you must then set pinion depth and preload. Is that strictly necessary if new bearings were not installed and just synchros were replaced? Also were is Reverse located on the main shaft? I'd like to examine the teeth and replace if required Any idea where I'd find a reverse gear if I needed one?

2nd, 3rd, and 4th gear synchros are available from vertex auto fro ~140 bucks, or I can do 1-4 for ~190.

That's chump change compared to ~3k for a used box or ~2k for a professional rebuild. I just need the box to run for a few more years till I'm done with school.

no need to re shim the box if your using the same bearings as nothing is changing and it should be fine.
The actual reverse gear is offset in the box, photo attached. you can see that the teeth have a pointed edge to them, if its squared off then this may be the issue. Usually we do 2nd and above synchro as 1st hardly get punished like the rest.
regards
Sean

Thanks Sean! I'm assuming the removal of reverse will be obvious with the pinion shaft out? I think I'm going to give this a shot. My only fear is I don't have the tool to hold the shaft while I remove the rear triple square tool that's behind the rear seal. Is that required; I don't see why a stout impact won't work?

The issues with reverse might be an alignment issue stemming from a previous, poorly done repair that I believe may be locating the shifter support/fulcrum lever improperly.


https://cimg8.ibsrv.net/gimg/rennlis...6ab7abfacf.jpg


Talking about this bit here. The issues with reverse started cropping up after this repair. Let me go grab the trans and put it on my bench and take some pictures of it so you all can get a better understanding of how it originally failed, how it was repaired, and what the hell I'm talking about.

There is a synchro for reverse, not in the usual sense, but the PET 6 does call the device a synchro, as it provides a synchronizing function. See part 52 in the attached. The reverse synchro does stop the free wheeling gear for shifting. A draging clutch will overpower the synchro. The way the trans is designed, with the requirement for each shift rod to be in neutral (home) position, before any shift, make the exterior shift linkage not part of any shifting issue. My normal approach for shifting to reverse is to cycle through 3rd to stop the main shaft spin, and then into reverse. As Sean said, often the reverse gears are pretty beat up so the gear faces do not help to align the gears. When new, these have nice sharp angles so the gears glide past each other. In Sean's picture, you can see some dulling of the sharp edge. Still serviceable. The device just to the right of the shinny teeth is the reverse synchro, on the reverse gear hub.

To hold the main shaft for assemby and disassemby, I took an old clutch, and bolted a 3 foot long piece of metal through the clutch media, to make a long lever. Works fine.

Sean your work is very helpful for all of us.

This is what I was talking about. The trans case actually cracked, and I had it TIG welded and redrilled. I'm wondering if it's a little off center/mislocated and that is contributing to my issues with the box.


https://cimg0.ibsrv.net/gimg/rennlis...a48a3d1bef.jpg


https://cimg1.ibsrv.net/gimg/rennlis...68591b9799.jpg


https://cimg2.ibsrv.net/gimg/rennlis...e22097d457.jpg

The external pivot has no role in how the gears shift. The pivot point is a driver (you) feel variation for how the shifter feels.

Take Sean's advice and replace synchros 2-4. You can verify the others are good per the factory minimum distance measurement from the synchro face to the gear.
.

Cool, thanks!

First things first, I'm going to give the trans a quick wash with dilute lye; yes I know it attacks aluminum but it works great to clean 30 years of grime off if you only let it sit for 5 minutes and then rinse with a hose.

Your right Alan, never looked at it that way.

After a 5 minute soak with dilute lye: Much cleaner!


https://cimg8.ibsrv.net/gimg/rennlis...998f987083.jpg

Remove just the input shaft
 

Thanks for the great writeup, all the pics really make a difference.

I am resplining the input shaft so the trans will mate directly to an Audi v8.
If I understand the pics properly, it appears I don't need to remove fifth gear? Just undo the shift shaft, then
I can just unbolt the gear section from the housing and slide back the gears, exposing the front of the input shaft?
This should be enough to machine the new splines. Thanks.

You could do that but i would be very careful that no metal filings make there way into the gearset. Is the Audi V8 significantly different spine count and size? i take it the shaft is smaller for the Audi?
Regards
Sean

Certainly will be careful to seal off behind the shaft. I may try to setup a rig to respline it without removing it from the case, but that might not be possible.

The shaft sticks out and can't mate with an engine directly as-is.
The splined part must be cut off, leaving the smaller diameter shaft to be resplined, and turns out a VR6 flywheel almost fits the Audi V8 and the VR6 clutch has the smaller splines that will work with the cut shaft.

A reasonable person would just use an automatic transaxle that just bolts up.

Are you shoehorning an Audi V8 into a 944? Is it for a street only car? If for a track car you could be better off looking at a different gearbox that will have more options available. Some of the Audi O1E 6 speed gearboxes have straight cut gears and even a poor man's sequential setup available.

From the looks of it Patrick i would say its possibly a kit car of some sort and he is mounting the 944 box directly to the back of the Audi V8. Very common to use these boxes for kits such as the GT40 reps.

I don't really want to pollute this fine thread with talk of my project, but yes originally was to shoehorn the audi v8 into a mid-engine 944. However, I have since decided to make it street legal, which in california pretty much means a pre-1976 car, and have choosen a 67 Corvair body for the drivetrain.

Right. Good Luck!!

First post and I'm very sorry to bring this back from the dead, but does anyone have the images from this walkthough?

Looking to get a 944 and options for bigger power is top of the research list

Cheers,
Matt

I have the images and complete page downloaded. With permission from OP I could create a PDF or something for download.

I would love to have the pics that come with this thread...

It would be great of the PDF file is attached to this the so the pictures will always be available.

I'm 100% sure the Buchanans wouldn't mind. You can check but Sean is overseas at the moment.

Okey, let's hope so :)

Here's a link to the PDF, it's in my Dropbox for the moment.
https://www.dropbox.com/s/3d2qmv1i0j...hread.pdf?dl=0

Is there any good way to host it on the forum instead?