928drvr86.5

First of all my thrust bearing is fine After 4 years and some change of ownership of my 86.5 I decided to check the preload on my flexplate. For some reason I hadn't really been aware of this common problem until this past spring when i started reading the threads. I think the reason i overlooked the various threads on the forum and the email list concerning thrust bearing failure is simply because is it usually referred to as TBF. Seeing TBF in the subject line was leading me to think the thread was about Timing Belt Failure, and being well aware of that subject i wasn't reading the threads.


When i checked my preload on the flexplate this spring for the first time ever during my ownership i had 3mm of preload pushing the flexplate forward. I checked the endplay there was only .008 " so, it was fine.

Today i decided to check the preload again, low and behold, another 3mm of load going into the flexplate but still only .008" of endplay. Only 3 months and 2000 miles since i checked it. I did not apply the loctite 242 method when i originally checked but I will do it the next time i check the flexplate. I will be checking it again in a couple hundred miles from now when my new modular crossover arrives for installation. It may not even get a couple hundred miles in that time because i noticed the radiator overflow plug that runs coolant back to the reservoir was cracked and leaking at the top of the radiator, so that is on order now too.

It's never ending

Another 3mm preload in just 2000 Miles??

928drvr86.5

I will be ordering a new clamp bolt for the flexplate as well.

m21sniper

I just ordered a whole cam tower gasket set today(smoke, cough, cough). I can relate to the 'never ending' part, lol.

Garth S

Loctite 290 will work as noted here .... but the 242 is neither likely to penetrate the splines nor hold. 242 could be applied to the pinch bolt ... but unlikely to achieve anything.

Bill Ball

Ben:

The flexplate and clamp are sold as a unit. There are notches in the flexplate that balance the pair. So, they should be changed as a pair. I have done it. It takes a lot of monkeying around. A new clamp won't help anyway. Your clamp is no different than anyone elses.

Many of us have found that 3MM of preload develops pretty quickly after you reset the clamp and doesn't seem to do any harm. Every time I check, no matter how long it has been, I find 3MM. I reset it for the hell of it, even though I know it will be back at 3MM shortly.

928drvr86.5

I was just going to replace the bolt, not the clamp, 928sp sells them. I think i got the Loctite 242 spec. from Cpt. Earl Gillstrom's site, if 290 will work better i will use that. So 3mm of preload is acceptable, that's good to know. I wonder what the equivalent strain would be with 3mm applied to the flexplate?

borland

How many miles do you have on your torque converter bearings?

m21sniper

What are torque converter bearings?

Bill Ball

Sure, get a new bolt. There is no good documentation on what is acceptable preload, if any. That's just what is commonly found.

I should add as an interesting data point...last weekend we undid the clamp on Rich Saunders 78, which had NEVER been undone before. It jumped a whopping 1/2 MM.

928s prior to 86 had a different TT that was slighly longer and included a shim and retainer on the end to prevented the TT from moving in the clamp. When you replace the TT get the early type - 928 International sells their rebuit TTs with the early shaft and you can install the shims and retainer.

borland brought up TC bearings. Mine are starting to whine. It is possible for the TC to move forward as the bearings wear. One of my upcoming projects will be to replace them and I will probably just put in an early TT at the same time. Snipe, here they are:

m21sniper

"928s prior to 86 had a different TT that was slighly longer and included a shim and trainner on the end to prevented the TT from moving in the clamp. When you replace the TT get the early type - 928 International sells their rebuit TTs with the early shaft and tou can install the shims and retainer."

God i'm glad i got an 83. I had NO IDEA about any of this stuff when i first got my 928, including the interference nature of the later motors. So when my t-belt went kaplooey while the car was running, it was just a matter of replacing it, instead of the whole engine.

Just for clarification, is it impossible for a pre 86 to have TT induced TBF failure, or just very unlikely?

I've never messed with my TT at all.

Bill Ball

It's not impossible. You have to futz up a tranny, TT or engine installation job. There is a procedure for setting the flexplate to flywheel clearances on early cars. Once set, you never need to look at it. As long as your drivetrain has not been messed with, leave it alone.

m21sniper

OK, thanx Bill.

Garth S

Ben,
Go read Earl's "#290" fix-it note. The #290 is was less viscous that water - and is used to effectively weld the splines in place: this is the downside if wishing to pull the assembly apart, for that's when the heat and hammers come into play. #242 is great for normal bolts.

928drvr86.5

Great replies, many thanks.

928drvr86.5

The converter bearings as well and Torque Tube bearings are original I'm sure and are now at 123K miles. I am not hearing any noise from the TT, but now i have to worry about those too? Like said... it's never ending.