what causes thrust bearing failure??

[an87ttype]

My thrust bearing failed after 3500mi on rebuild! I assume the transmission or converter is probably to blame.
The motor is out of the car. How can I figure out what the problem is? I can't see anything obvious on the flyweel or converter. The converter is an AC 9" nl. There was at least 3/16 inch clearance when I pushed it back from the flywheel.
What gives?!?

 

[BoostKillsStres]

When the engine was assembled were the faces of the thrust bearing seated against the crank face by installing the thrust bearing cap just snug then forcing the crank fore and aft to line up the thrust surfaces then torquing to spec?

If one half of the bearing thrust surface is worn and not the other this could be a sign of an installation problem.
HTH

 

[buickboy]

Torque convertor Ballooning is 1 cause.
Mitch

 

[JeffG]

Do a search in the general tech area under "thrust bearing ". There is a lot of info in there. Seems that high line pressure can do it too........pushes the converter into the crank.

Hope that helps,

 

[an87ttype]

Does a converter balloon and then shrink back? Or does it stay ballooned?
I was assuming it would stay enlarged and I could see or measure it. Mine looks fine. Any other way to verify??
Thanks all............

 

[an87ttype]

Any other ideas what to check before I put the motor back in??
I don't want this to happen again.
Thanks...........

 

[JDEstill]

Here's a helpful link that someone posted a while back - some good info here:

http://www.aera.org/Tech/tb1465r.htm

John Estill

 

[bruce]

The converter just floats on the tranny end of things, or should we say has lots of end play since it's spines that locates it. It is however bolted to the crank.

As line pressures increase the converter is pushed forward. This pushing forward of the converter is what eats up the thrust bearings, assuming the machining was correct.

Lots of trannies are improved by just running the line pressures up rather then changing the rates at which the prssures are applied, AND released. That's why some tranny rebuilds are $500 and some are $900.

And power braking really increases the problem. having a chip with a launch strategy, or redoing the stock calibration to get a serious launch strategy takes alot of time.

You can launch at 15 PSI making serious HP, or you can launch at 15 PSI with alot less HP, and just have the turbo spooled in preperation of going quick. 15 PSI can take a host of meanings when power braking.

 

[JeffG]

John,
Thanks for the link. The parallel cooler and breaging modification seem like great tips. The excessive voltage thing is hard to swallow though........but interesting too.

 

[an87ttype]

Thanks for the link!
It sounds like I have to put it all back together to check the line pressure. If the front pump needs work then I have to take it all out again.
What can I check now that its apart so I only have to do this once?
Thanks..........

 

[an87ttype]

TTT