torque converter - thrust bearing - catastrophe

[gwcrim]

Last fall I had a local trans shop R&R the 200-4R out of my C10 for some fixing.  Its' been working quite well since.  This summer the engine pushed a head gasket and since it was also leaking oil worse than the Exxon Valdez, I decided to pull it out and look it all over. The engine only has about 5000 miles on it from a total rebuild, so the last thing I expected to find was.... a bad crank thrust bearing.  Since the engine is out, it's not a huge issue to fix BUT what caused it?

From what I understand, the converter sometimes does not always fully slip into the transmission.  That sure would ruin the bearing.  My big concern is what damage might this have done to the transmission?

What else should I be concerned about?

[JohnnyPopper]

I take it that the damage came from the direction of the rear? How bad is it, can you post pics?

[gwcrim]

Sorry, no pics.  Nothing really to look at.  I suppose I'll pull the trans and have it looked at.

[bd]

If you think the converter was installed incorrectly, just unbolt it from the flexplate with the transmission installed and see whether the converter will slide rearward, away from the flexplate. 

Causes for excess crankshaft end play vary considerably; a few follow.  If the crank thrust bearing is worn out, look for evidence of inadequate lubrication, inadequate crankshaft thrust faces spacing, rough thrust surfaces on the crankshaft due to shoddy machine work, wrong bearings, interference between the converter pilot and the crankshaft, wrong converter, excessive automatic transmission pump pressure, improper mounting of engine driven accessories - essentially, anything that applies undue axial pressure to the end of the crankshaft.  If the crank thrust bearing faces exhibit normal wear, look for wrong bearings, check the thrust bearing fitment to the block, and look for improper machining of the crankshaft thrust faces spacing.

[gwcrim]

Thanks BD.  The engine is back at the machinist.  He's a pretty good engine builder, does lot of race and hi performance stuff.  The crank was brand new at the build.  Not saying it didn't have an issue though.

The guy who installed the transmission didn't even recall doing it but he's been in the business for years. He said they always spin the converter around before bolting it to the flex plate to make sure it's not binding.  He said he'd check the trans out if I brought it to him.

The converter is maybe a 2400 stall and I really don't beat on it.  The converter and trans came from Vince Janis out of Akron.  He's nationally known as a go to guy for serious 200-4R builds in the turbo Buick world.

Hopefully the machinist will be able to diagnose the issue. 

[gwcrim]

In my last topic I shared the story of my bad thrust bearing.  I'm still searching for an answer.  Here's a possibility.  The drive shaft is too long.  Not by a lot but it barely fits in. Maybe 1/4 to 1/2 inch too long.  Is it possible that it would have put pressure on the converter and then on to the engine thrust bearing?

[JohnnyPopper]

I'm not an expert AT ALL, but that would mean that the extra thrust would affect all of the components from the tail shaft to the spring plate. I would expect that you would have more problems than just the thrust bearing.

[SilverMiner]

I agree with JohnnyPopper, and actually have second-hand experience with a too long driveshaft. If in fact your driveshaft was too long and had jammed into the rear of the transmission and then into the engine, you would have known it the instant it occurred. A buddy of mine had this happen in his 71 Buick GS while I was a passenger, and you wouldn't believe the horrible sounds it made as the rear suspension compressed and shoved the driveshaft into the trans. In his case the damage was all contained (and absorbed) by the TH400 trans. I hope to never hear that noise again.

[gwcrim]

Here's another bit I just recalled.  The first slip yoke I put on that driveshaft mysteriously lost the press in plug/cap.

You guys may be right but since the engine's out I'll have the trans inspected and re-measure the driveshaft.  There aren't many things that cause a thrust bearing to wear out in 5000 miles.  I really need to find the culprit.