Mike C.

I'm slowly disassembling my car's original (5 sp) transaxle which expired due to pinion gear failure. I couldn't just toss it out without seeing how far I could get in taking it apart (with help from Factory shop manual). So far, the only 'special' tools I've needed were a (cheap) gear puller and good snap ring pliers. A set of punches/drifts are helpful too. If I were serious about being able to re-assemble, I would need to acquire a hydraulic press and the ability to heat gears to 120 C or so (A hot plate would do the trick). Where the procedure truly leaves the realm of the capable DIY mechanic is the replacement of the pinion bearing race in the aluminum transmission case (heat case to 150 C, press in race) and the adjustment of ring and pinion mesh via shims behind the pinion shaft bearing races and differential bearing races. This requires some very special tools to get the correct measurements, particularly the axial position of the pinion shaft. This is also a critical adjustment for R&P longevity. R & P sets are always sold in matched pairs and are marked with specific information as to how each set compares to a factory standard gear set. This is apparently how the manufacturing tolerances are held. According to the FSM, the deviation 'r' from the 'master gear' is inscribed on the ring gear end face as a 2 digit number representing hundreths of a mm.. The FSM also says that only replacement gear sets will have this info inscribed and that original production gears will not. Well, in my case either the latter isn't always true or sometime before I bought the car (with 40K miles), someone had the R&P replaced because the deviation number is (hand) scribed on the ring gear. This has me wondering... If I were able to purchase an R&P set with the same, or very close to same deviation as my gear set and I were to re-use all of the pertinent tapered roller bearings and races (which all look fine BTW), could I install this gearset without having to re-adjust the R & P (and get proper mesh) ? In other words, if I leave the adjustment shims as they are presently and put in a gear set with the same deviation, will the gears be happy? If anyone has any experience in this area, I'd like to hear from you....

badcoupe

they would be close, some gear marking compound would tell the story. I'm doing my trans right now and do alot of rear wheel drive ring and pinion jobs so I have some experience in this field. the hassle is continually dissasembling and reassemling it for backlash preload checks etc before final assembly and sealing. The pinion bearing race on all the p-car trannies I've tore have came right out without a fuss by hand. You can go to a machine shop and have them cut shims for you of any htickness provided they have have the thickness of shimstock on hand you desire. You can shim the pinion bearing race in the case up to tighten the shaft or remove pinion depth. Removing shims will also the oppssite affect. I think it's best to get the pinion depth correct first then if the shaft is too loose or tight change the shims for the rear pinion bearing race at the rear of the iron case. Again the requires tedious assy and disassy.

Scott at Team Harco

Mike,

There are a few of us here who have rebuilt their transaxles. It is possible to do it with enough good tools and lots of patience. You may want to do a search for more background.

Tifosiman (Jeremy) had his R & P break on him a few months ago. He has, by now, collected enough information to write a book. You would do well to get him involved in the discussion as well.

And as Badcoupe points out, you will need to do a lot of assembly and disassembly to verify proper bearing preload AND proper gear mesh. You can't get away with one or the other - you MUST have both at the same time. That is what makes it more difficult than simply bolting things together.

Keep asking questions. There is good information here.

Best of luck.

Mike C.

badcoupe, I can see getting the pinion bearing race out of the transaxle case without heating but putting it back in? This would seem to be the key issue if one doesn't have an oven large enough (or a wife understanding enough) to fit a trans case. It does seem logical that you would want to get the pinion depth controlling shim determined first and then work the bearing pre-load from the gear case end. As for repeated assembly/disassembly, it seems you would only need to install the pinion shaft and not the input shaft to perform the mesh checks (or am I wrong?). If so, it wouldn't be so bad. Is it possible to get a reasonable mesh determination without the gears being under load? I seem to remember some kind of goop you put on the gears to tell how they are meshing - does anyone know what it's called? How about the torque check for pinion bearing pre-load? Is this easily done with a common torque wrench? Am I feeling lucky enough to roll the dice and spend $500 on a new R&P set ???? It certainly would be a fun winter project...

badcoupe

your right by saying that you would only need to install the pinion. You are also right about the mesh then preload. just simply bolting the cases together will give you preload as the rear bearing is pressed on the shaft and no bolt holds it on. The gear on the back of the shaft has a spacer on it so it has no bearing on preload. Most speed shops should have some marking compound just ask for gear markinmg compound. White lube also works well. The pinion bearing race simply goes right back in by hand, I've had to tap on it once with a hammer handle as it wasn't perfectly straight. Hope this helps. If you weren't so far away I'd get together with you and help as I've been through this enough I can nearly do it blindfolded! The only problem with assembling the pinion is you'll need a press to press some of the gears back on. A good auto machine shop should be able to do this for you. Take them both at the same time and have him transfer everything over. I might be able to get you a good used R&P with the pinion shaft and gears still assembled.

Scott at Team Harco

The stuff I used to check gear mesh is called Zinc Oxide. You can get it at most any pharmacy. It's the stuff you see on the noses of lifeguards.

In my opinion, it would be worth the effort to rebuild your transaxle. As you mention, you'll need to plunk down a little now to get the ring & pinion - but you'll have a great feeling of accomplishment and satisfaction when you are done.

Best of luck.

Mike C.

Zinc Oxide? Who'd a thunk it... Thanks Scott. I'm going to see how difficult it is to remove and re-install the pinion bearing race. If this proves to be easier than the FSM procedure (bake transaxle case at 150 C, brown evenly...), I plan to go ahead and shop for a new R&P. I have access to a hydraulic press at work, so I'm covered there. I have dug up some information from various other car maker's shop manuals describing the gear mesh patterns that show proper meshing of the hypoid gears. Hopefully, I'll be able to decipher the zinc oxide patterns properly.... I'll take some photos too.. if my hands aren't to greasy....

Mike C.

Tifosiman are you out there? Your experience with this subject would be appreciated...

Mike C.

I noticed I was getting a bit of ribbing over on the e-mail list for even contemplating this project. Gee that's the spirit... As if I would re-use bearings even if they sustained damage from the pinion fragments getting around.. It so happens that only one tooth broke off the pinion and no damage occurred elsewhere in the transmission (as proven by disassembly). I didn't drive it but a few feet after it occurred. Give me some credit please..... I still think it is a legitimate question as to the attempt to match the pinion devition on the new gear set so as to minimize shim changes. The idea of looking at gear mesh patterns (with zinc oxide or some other visual enhancement) is not really so primitive as some would make it out to be. Even if you do own the fancy pinion position measuring tool, I think it would be foolish not to check gear mesh pattern visually in case of a shim calculation error, etc. Pre-load doesn't tell the whole story - it simply says you have the proper pre-load on the pinion shaft bearings. Even if I do ultimately waste $700-800 on parts, I already know a hell of a lot more about transaxles than I did before....

badcoupe

Mike go for it anyway. just take your time and take notes as you go along if need be. Blowup some of the diagrams and keep them handy. It's easy to sometimes get going and forget a snapring or something. Gear patterns are somewhat easy, use your old ring and pinion for reference as to pinion depth and wear pattern.

Mike C.

Thanks BC. Getting a wear pattern on the original R&P is a good idea. It'll give me some practice putting things back together...

Scott at Team Harco

Mike,

Don't let the nay-sayers influence you in any way. A trans rebuild is something the competent and careful mechanic can accomplish. You've got enough experienced people here to help you through it. Just keep moving forward and ask questions if you get stuck.

tifosiman

Mike, sorry I jumped into this late, I haven't been posting on Renn as much as usual lately and therefor have not taken the time to look at a lot of threads.

It sounds like you pretty much have this covered and are on the right track. The FSM has all of the info you need to know. Provided that you have access to a press, and can make/buy the proper tools, you should be able to do it right if you take your time. If it already hasn't been mentioned, a hotplate is helpful for heating the gears before pressing them on the pinion shaft.

Should you be in need of the rear black seal that you had to pop out (and had to poke a hole thru to get it out), or any bearings, there is an ebay seller by the name of "blonde99" or "blonde69" or something like that, that has a seemingly endless supply of 944 trans pieces as new up for sale on ebay all of the time for good prices (I think she bought a huge stockpile of parts from a shop that went out of business).

There are severall threads on this that have a lot of info and dialogue between Scott and myself, take a quick gander by searching.

There is a good chance that your trans was cracked open and worked on at some point prior to your purchase of the car. The factory recommended that at certain intervals (40K or 45K depending on the sources) the transmission be opened up and checked for proper pre-load, and additional shims added to the r&p if necessary (since teeth wear over time and the load changes). This step has been ignored over time as these cars get older. Add that to the problem many cars had with the rubber clutch center going bye-bye and putting even more of a strain on the trans, and you can see why so many 944 transmissions have taken a dump.

What year is your 944? I bet it is earlier than an 88, correct? I appears that the 88 and 89 cars were spec'd with ROW transmissions (different part#'s with stronger r&p's). There are much fewer incidents of failures with those years.

Take pics along the way during disassembly and reassembly, that will be very helpful.

BTW, for an additional $200 ($700 total), PowerHaus II sells a hardened and cryo'd r&p set, might consider that while you are doing all of the work.............................

Good luck!

97xray

Mike, where are you actually located?
My wife and I are moving, but we're not gone yet. There are a few of us within ~1 hour (East) of Hartford.

Mike C.

Thanks for the input and encouragement Tifo. I will certainly try and look up that e-bay seller. You are correct that my 944 is pre-88 (early 85). I did buy the car from the original owner and have records but no sign of transaxle work being done. The pinion gave up at around 175K miles which really isn't too shabby. Luckily, there is no consequential damage from the loose tooth. Luckily I have access to a metal lathe and hydraulic press at work. I'm currently making a bearing race puller for the pinion roller bearing (for the slide hammer). Once I'm sure this bearing race can be removed and re-installed without too much trouble, I'll be shopping for parts.....

97xray, I'm down in the New London area.