Mike C.

The spider gears were fine. As soon as the 'event' occurred, I didn't drive more than 50 feet. I recognized what had happened quickly and so probably minimized the consequential damage. Or maybe I was just lucky that the damage didn't go beyond the R & P. I'd never heard that the spider gears were suspect. I always thought it was a marginal R & P.

Mike C.

Bob, If you are going to take apart the unit enough to do a thorough re-seal, you might want to take a close look at the R & P with zyglo. This is a flourecent dye pentrant that is widely used to look for fatigue cracks with a 'black' light. It would require cleaning the gears well but should be do-able, especially if you remove the gear box from the trans housing. I believe some machine shops offer the service (we have it at work). It might show up impending R & P cracks and save you some time. Magnaflux is also used on steel parts but I'm not sure if it works well on gears.

badcoupe

zyglo is primarily used by automotive machine shops for aluminum as magnaflux doesn't work. You could mag or zyglo the gears either should be sufficient.

Mike C.

A question for those of you who have tackled the transaxle rebuild. How did you determine you had the correct pre-load on the pinion shaft bearings? The factory manual says you should end up with a reading of 200 - 400 Ncm using the factory torque-o-meter. Natrually, this little device is a king's ransom. I've been told it can't be done properly with a regular torque wrench although it's not obvious to me why a small, in-lb range bending beam torque wrench cannot get me within +/- 100 Ncm of the target (that's 18 to 36 in-lb). I would welcome any innovative approaches or mechanics intuition on getting this correct.

shmucklebuckle

I read someone said "don't do that" somewhere the other day...but that's all I know. I don't see why it woudln't work either.

Mike C.

In case anyone is interested, I did find a web site describing a checy truck axle rebuild that has some good information - they use an in-lb torque wrench to measure pinion bearing pre-load. I believe this will do it. http://www.fullsizechevy.com/fscu/axletech/

Scott at Team Harco

The use of a very (VERY) fine beam torque wrench can give you an idea how close you are to spec. However, I would suggest a different technique.

This will definitely work for the pinion side of things. I don't recall if I did the pinion. I think my pinion (fore/aft) location did not need adjustment.

1) Remove the bearing races and take out all the shims. In place of the shims locate 2 or three small pieces of electrical solder (about 1/4" long segments) equally spaced around the housing. Use a small dab of grease if the solder wants to roll away. Carefully place the races back and assemble the trans as normal.
2) Torque all fasteners to spec. Rotate the input shaft a coupe of times if possible.
3) Disassemble the trans being very careful not to lose the solder. Carefully remove the solder segements and measure their thickness with a caliper or micrometer. Record these numbers and compare them against the specified perload numbers in the service manual.
4) The thickness of the solder plus the amount of preload will tell you the theoretical total shim thickness required. I say theoretical because in reality this will tend to provide too much preload and tend to restrict motion.
5) Use the calculated numbers as a starting point for installing shims. Keep in mind that you must balance the location (in/out, fore/aft) by taking some shim from one side and adding it to the opposite side. This will keep the contact patch (gear mesh) where you want it.
6) Final preload can actually be determined quite well by "feel". Install the axle flanges into the differential and use them to gauge the amount of resistance to rotation that exists. Turn the input shaft by hand - feel the ease of motion, or lack there of. Keep messing with shim thicknesses until you get the ease of motion desired (usually, this means reducing shim thickness from the theoretical values). Take your time with this step. Repeat as many times as needed until it is right. Double check gear mesh frequently. You may get tired of assembling and disassembling so many times - as it may take several tries to get everything right.
7) When the right amount of preload exists, it will require constant force to rotate the shaft. It should not be too difficult to get things rotating - but it should not spin freely either.

I know it sounds a little vague and subjective. It is something that is learned from experience. If you are uncomfortable doing this by yourself - you may want to take it to an experienced transmission mechanic in your area and have them give the thing a "twist". Once you confirmed the gear mesh - the preload is relatively easy to sort out.

Good luck.

Mike C.

Thanks Scott. I'll try it both ways.

Mike C.

I know I know... when is this transaxle rebuild post going away?

Well I installed my aft pinion shims and bearing, bolted things
together and did a quick test with the 'click' torque wrench - I get
somewhere around 18-20 in-lb before it clicks and the shaft rotates.
We'll see what I get once my 0-60 in-lb bending beam torque wrench gets
here. From the way some non-Porsche web sites have described it, I'm
pretty sure I'm in the ballpark. I estimated zero pre-load at about
0.017", then added 0.007 to that (which is less than the 0.011" pre-load
specified in the FSM). I can go another 0.003 with the shims I have on
hand. Those who've been there, what do you think? Is it preferable to
set up on the high side rather than the low of the 200-400 Ncm band?
Also, any recommendations on getting the bearing race out again without
destroying the shims in the process? Using a brass drift to remove the
original race (tapping a little on each side, etc.) ends up squishing
the shims in this area. There is not enough race peeking out from under
the flange to push on with a press - at least not with aluminum or brass
which deform enough try and go through the ID. If you use a press and a
suitably sized bar across the two exposed areas of race, will it come
out without damaging the shims? Will heat help or does it get
transferred to the race too fast?

Mike C.

After a couple of iterations with shims, I have the final pre-load at 30 in-lb (340 Ncm). I've also measured the R&P backlash (on the original diff bearings) using my knock off of the factory tool. 5 thousandths on the button. Now if I can just get the differential shims set up to get this backlash and 200 Ncm of pre-load on the new bearings, I'll be past the 1/2 way point. I think the gear patterns look pretty good too.

Sam Lin

Mike, I for one am enjoying this post, and don't want to see it "go away." Nice to see someone step-by-stepping this with pics.

Sam

Mike C.

Thanks Sam. Sometimes the lack of response makes me wonder. I did notice it gets a lot of views though...

Mike C.

More progress and photos. I am satisfied with the R & P mesh and backlash measurements and have commenced putting the gearbox back together. Note that the reverse gear sychronizer in the first pic is installed wrong (even though the FSM shows it in this orientation). It needed to be rotated 180 so that it wouldn't interfere with reverse gear on the pinion shaft. The 3rd pic shows the input shaft with 3rd gear and the new synchronizer installed. Note 4th gear with new synchro (brass colored thing) in the upper left of pic. Finally, the assembled input shaft.

Mike C.

Progress from the last two days. Almost there!

Bob Ward

I have heard that by treating the trans components using cryogenic metal processing really make a difference in durability.

Anybody try this?? Since it is so hard/impossible to buy race parts seems like treating the stock parts would be helpful??