Bill Ball

I left the two rear bolts out. When I shortened them as 123 mentions, they were no longer able to engage the threads in the bellhousing. In other words, the space between the exhaust and bellhousing cover is really tight on my car - less than the thickness of the cover.

Does leaving the bolts out do any harm? I don't think so. Mine have been out for 90K miles.

Bill Ball

Rog:

Sorry I missed this earlier. Shims are only relevant to the early TT design that was eliminated in 86, although cars continued to have the same shaft (w/o shims installed) for a few years. The shims go on the very front of the early central shaft. forward of the flexplate. Some of us choose to use the early shaft design and shims in later cars. The procedure for correctly setting the shims up is a bit obtuse to me, but it's in the WSM. Doing a TT on an 89 would not involve shims unless you requested an early design TT from the rebuild vendor. If you are rebuilding an 89 TT yourself, then there would be no shims, of course.

PorKen

IIRC, the shims are gone in '85.

Whatever year you have, shims or not, check the flexplate!

I just checked my '81 for the first time, and it was bowed. It moved a few mm's when I released it.

Bill Ball

Something possessed me today to check the endplay again, 6 months after I started this thread. My starter has been turning over a bit more slowly lately, although that is probably due to the 6+ year old battery. Regardless, that's not a common symptom of TBF. The hard starting from TBF is seen once the motor is warm. Anyway, I popped the bellhousing cover off and proceeded.

Without my contacts in, the flexplate looked a bit bowed forward. However, a straightedge showed it to be flat. Releasing the clamp showed no movement. Usually I get a couple of mm, but nothing this time. Note that almost all the shaft splines are now hidden in the clamp. This has happened over years, I speculate from something changing in the torque converter, commonly called "ballooning", which some doubt happens but many AT experts say is real. Maybe that has stopped.

Then I positioned my dial gage and took readings several times. With the flywheel levered forward, I zero'd the gage, then levered it rearward. The difference was 0.007in. I got 0.008in last time. Anyway, that is a very, very low 0.18mm. (Wear limit 0.40mm). My entire drivetrain is original and now has 187K miles on it. Seems to be holding up very well considering I'm not easy on it.

Black Sea RD

Bill,

I truly believe if the torque converter ballooned that much you would have noticed other symptoms like aluminum shavings coming out of the little grate on the torque converter housing, probably some noise from the rear flexplate bolts hitting the inside of the torque converter housing, bearing noise from the torque converter housing bearings, as well as the rear pinch bolt no longer being lined up in the torque tube hole used to remove it for transmission removal. Probably other stuff too. Any of these noticed by you?

Be interesting to see what is found when you finally tear into the transmission and look at the torque converter.

Charley B

Constantine, I tend to agree with you, but how do you account for the difference? And what would the limit be?

Black Sea RD

Hi Charley,

Hard to tell unless one does a comprehensive tear down of the transmission and checks the torque converter and housing. I studied our auto trans and transaxle driveline with my learning culminating in observing and partially helping in the complete tear down and rebuild of my 1986.5 928S track auto transmission before I did the 5 speed conversion to the car. The way the TC flexplate is pressed into the TC housing bearings and how tight of a fit everything is would almost certainly give some indication something is not right with the transmission after awhile of it operating under this sort of tension. The Porsche manuals even have a warning about bad things happening if the TC is not installed to it's full depth after it is removed and replaced.

Still we don't really know how much the driveshaft has moved forward unless Bill measured how much it moved over the years. Perplexing it is...

Bill Ball

I do have a bearing whine that I believe is the TC bearing. However, it started 3 or 4 years ago and has been stable. The noise is present in park and neutral but goes away once I put the car in gear and the drivetrain loads up. I haven't checked the rear clamp bolt in ages - I'l take a look at that. I'd say the total movement is about 1/2 inch since I got the car 8 years ago.

IcemanG17

The 1st time I met Bill back in January 2005 I "helped" (mostly watched) him release the flexplate tension.....I remember there was WAY more splines exposed back then.....but that was over 50k miles ago too..... But if it ain't broke don't fix it!!

Maybe the reduced torque from the non-boosted engine didn't make the driveshaft move??? Time to put the SC back on!!

Bill Ball

Here's a pic from early 2004. I'd say there's slightly less than a quarter inch more showing.

Black Sea RD

Hi Bill,

Yep, that's a lot. You also have the newer style driveshaft that has a tendency to shear at the neck down portion. Looking at your little burnout video it is surprising everything held together as long as it has with the miles and being SC'd. Others have not been so lucky.

Good luck with the investigation,
Constantine

Imo000

I could be wrong but I think Bill did snap the drivesahft once before and it was right at the end of teh front splines.


Would be interesting to see if the splines in the rear coupler moved out at all. Also if it was possible to measure the total length of the drive shaft over the years, it would answer the question if the TC is balooning or just the shaft gets longer from twisting.

Bill Ball

No, my TT shaft is completely original. You're remembering the one I helped replace locally. Matt snapped the TT shaft right at the neckdown on his 91 while entering a parking lot at low speed in a completely unabused low mile car.

Mine has survived 3 incidents of driving with the ignition monitoring system triggered, which is said by Porsche to break TT shafts in automatics, as well as repeated burnouts and mile after mile of flat-out driving. Maybe mine has been "work-hardened."

That photo is 4+ years after I bought the car. I remember another 1/4" of spline showing when I first got the car in late 99, but I can't find any earlier photos to prove it.

I'll try to get under there later today and look at the rear coupler.

Bill Ball

The rear coupler appears to be just where it should be. I couldn't get a photo of it as I could only get a view of it with a mirror without removing the rear exhaust to remove the heatshields.

So, that would argue that the TC has not ballooned and the shaft has not moved.

Black Sea RD

Mercedes transmissions are very robust and their TCs hardly balloon from the techs I talked too. There is a higher incidence with domestic TCs doing so.

Hmmm, strange indeed. Good thing the engine play seems good.

Contrary to what some say, the driveshafts do not lengthen with age or use. Metal will lenghten after it is stressed to it's breaking point, much like a paper clip will just before it breaks after bending it back and forth. Our driveshafts do not fracture/deform in this mannner to lengthen appreciably.

Constantine