Does anyone have a good write up on a differential install? Thanks.

 

Wow, there has never been a write up on a differential install on a 951?

 

Its a black arts kind of job... rumors of tens of thousands of dollars worth of tools, and blood sacrifices abound. You have to get the preload on the bears set JUST so... and for the most part, its beyond the abilities of the average home mechanic. I haven't heard of too many successful home swaps.

If you are talking about just a transaxle swap, then thats a different story...

Regards,

 

Been there,done that,but never written anything about it... Well,I can write instructions for you in Finnish,but I doubt that it's not what you want.And the same in English takes too much time....
Basically it's pretty staight-forward job after you've taken the gearbox out of the car.Someone tells you how to do this...
Things you need beside that lsd are new main shaft gasket,new bearings beside the lsd ( both sides,SKF has them,use old ones as a model),some good-quality sealig glue (Lock-Tite "green one") and oil.

Things to do (just the basic things):
Drain out old oil.
Remove drive shaft "stubs".
Open the cover on alloy housing (rhd side).
Disconnect gear selector rod connection.
Split the gear box (black iron part) from that alloy housing.
Remove old diff.
Remove old bearings.
Remove the ring gear from old diff.
Assembly in reverse order...

No special tools required,this part takes time from about 30 minutes (experienced mechanic) to 4-6 hours...and some beer.

Remember to clean all parts thoroughly,use sealing glue where needed,main shaft gasket is the last thing to install prior adding new oil and use ring & pinion gears in pairs,ie both old or both new,do not mix!

Oh,now you did it...I wrote it!

I might have missed forget something,I've done it only once 4 months ago,but it still works!

Have fun!

 

If you DON'T touch the gearbox itself and you DO use matching ring & pinion,there's no gear tensioning or preload measuring.Just use common sense,good advice from qualified Porsche-mechanic and refer to the Factory Shop Manual.

 

Don't do it.

Buy a transmission with a LSD already installed.


I can tell you horror stories about my experiences and there are people on this list that will tell you the same thing...

"It ain't ever the same once you touch it"


Oliver... you around? Your story would be nice to insert here....

 

Oliver's story is a great cautionary tale about tranny rebuilds but I think it's really more about the dangers of who is doing the work as opposed to having work done on a 951 tranny.

The last rebuild, done by a meticulous mechanic in spare time, seems to be holding up exactly as desired.

The challenge to buying a tranny that already has an LSD is finding one that won't need to be opened soon, anyway. These cars (and their trannys) are only getting older so it's becoming harder to find one in good condition. The clutch plates in an LSD do wear and require rebuilds at some point depending on usage. Syncrho's wear, seals go, etc. One could also make the argument that a torsen diff like a quaiffe or GT would be a better choice over LSD for most people.

To me it ends up being half a dozen of one, six of the other.

 

I('ve done it it's not too bad but after installing the new bearings I had to do some shimming as the backlash wasn't correct because the new bearings sat the diff. somewhat closer to the pinion. It would've been ok where it was but I like a little more backlash than what I had.

 

Trannies are funny - they're simple to rebuild when you know what you're doing, and extremely fragile and complicated when you don't. As long as the backlash is correct, I don't forsee a problem with swapping the LSD. Best of luck.

 

My current tranny (which has been very reliable even with my abuse) came without an LSD. The LSD from my original broken tranny was removed and installed in this tranny the first week I got the unit. No horror stories here .

 

You ABSOLUTELY do not want to just slam a diff into your trans. This board gives good info more often than not but in this case some are steering you toward disaster.

You MUST check the differential drag (or bearing preload), you MUST check the ring and pinion backlash as well. Don't risk destroying your trans for the very outside chance that it will be OK. Find someone who has the necessary tools to set it up correctly or send it to a shop and have it done for you. I do this stuff quite a bit and cannot remember the last time I got lucky enough not to have to repeatedly press bearings on and off to re-shim the differential.

 

rage

I've got a LSD tranny with cooler... $1100 + shipping

and... I would highly recommend this over changing out the differential.


If you don't buy it from me, buy it from someone else... but buy one and just install the entire thing!

It will be far cheaper in the long run...

 

I was just stating at my success with dropping the LSD from my original tranny to the current used non LSD tranny that I'm using. I've ran it for 3 years now, daily driven, roadcoursed, drag raced, all sorts of abuse and it's held up fine.

I purchased a Rothman's Cup Car tranny about 8 months ago that I haven't put in yet. Heard it was stronger, and will be installing it when I decide to put in that 2.8L block .

 

The factory manual is a must for the diassembly/assembly, and also explains the ring/pinion setting.

You can open up a gear box, change out all the input shaft bearings and synchros without a problem. Where you have to worry about the ring/pinion spacing, is when you change the differential bearings and the pinion bearings.

For swapping a differential you need to check/adjust the ring-pinion distance even if you are using the old ring gear on the new diff. Replace the diff bearings, and if youre in there, you might as well replace the pinion bearings ($75-$100 ea for the pinion bearings) and youll have a good rebuilt trans.

You can do most of the disassembly yourself (removing the gears on the pinion shaft requires a press), then take it to a reputable porsche shop and have them set the ring/pinion distance for you. It can be several hours of labor, so it wont be cheap. So that is the decision point on whether to go with a used tranny or with the diff install/rebuild. Really depends on the condition of the used tranny. If its worn, youll have to do a rebuild anyway.

Ive done both: 1) installing a quaife in a non-LSD transmission during a rebuild. 2) Buying a used Turbo S trans, rebuilt it to replace a non-LSD transmission. I needed knowledgeable shop help for both.

 

so it seems that pete95zhn from Finlad did it without problem and it still works. he just took one out and put the new LSD in.
where is the Problem?
My questionis?
Can it be done with the gear box still on the car or should one take the gear box out of the car?
I think it is possible.
I want to put a LSD in a trany with nO LSD and no oil cooler and do NOT removed it from teh car since I just install it last month

Konstantin