81' thrust bearing failure
Thread Starter
Instructor
Joined: May 2004
Posts: 187
Likes: 0
From: Fort Drum New York
81' thrust bearing failure
I have a problem with the stock motor on my 81. 1 year ago my wife and I converted it from auto to a 4 speed. Shortly after an issue with the crankshaft presented itself. Coming to a stop with the clutch in, the clutch would suddenly reengage even though you had the peddle in. After pulling the engine out, we found that the thrust bearing surface on the crank was worn down (but oddly the bearing itself was perfect) our theory was that they auto tranny had been out of the car and the washers on the torque converter were put in on the wrong side of the flex plate. (Creating a push on the crank as you drove)
Here is where I get confused.... we replaced the crank and put it all back together. 2500 miles or so later, the problem is coming back. This time I know it’s not the flex plate. As far as I know nothing could put pressure on the crank to cause that. Is my engine eating trust bearings? Any ideas? The tranny isn’t a t-10 it’s a Saginaw. (A t-10 is in the works) is the tranny input shaft to long and pushing on the crank? Thanks for any ideas
Robert Dallas
81 Vette
00' TA mmmmm LS1's mmmmm..
Here is where I get confused.... we replaced the crank and put it all back together. 2500 miles or so later, the problem is coming back. This time I know it’s not the flex plate. As far as I know nothing could put pressure on the crank to cause that. Is my engine eating trust bearings? Any ideas? The tranny isn’t a t-10 it’s a Saginaw. (A t-10 is in the works) is the tranny input shaft to long and pushing on the crank? Thanks for any ideas
Robert Dallas
81 Vette
00' TA mmmmm LS1's mmmmm..
Thread Starter
Instructor
Joined: May 2004
Posts: 187
Likes: 0
From: Fort Drum New York
Using a brass bushing for the pilot bearing. Havent had a chance to pull the tranny back out. but you can put a screwdriver behind the balencer and shift the crank back and forth a small bit. (you could do this a full 1/8in when the thrust bearing died before)
<scatches head>
Robert
<scatches head>
Robert
Race Director
Joined: Jan 2000
Posts: 13,018
Likes: 2,262
From: Corsicana, Tx
2020 C2 of the Year - Modified Winner
2020 Corvette of the Year (performance mods)
C2 of Year Winner (performance mods) 2019
2017 C2 of Year Finalist
Sounds more like clkutch linkage geometry/binding issues. When you depress clutch the crank is shoved forward and then the fingers of pressure plate release the disc. Sounds like maybe the throwout arm is contacting the bellhousing, or maybe there is not enough freeplay? Sometimes when geometry/stud length is off, you end up taking all freeplay out to get it to release. That holds crank against bearing all the time.
Have someone depress clutch and visually check freeplay through throwout arm hole with a mirror if necessary and then watch it as it is depressed. Make sure all the linkage doesn't bottom out on any part of bellhousing, trans or floorboards, headers etc etc etc.
When you pull trans, look at pilot bearing closely and do some measuring, but I doubt there is an issue there unless it's some oddball trans, but even the ones from Vegas worked OK it seems like.
JIM
Have someone depress clutch and visually check freeplay through throwout arm hole with a mirror if necessary and then watch it as it is depressed. Make sure all the linkage doesn't bottom out on any part of bellhousing, trans or floorboards, headers etc etc etc.
When you pull trans, look at pilot bearing closely and do some measuring, but I doubt there is an issue there unless it's some oddball trans, but even the ones from Vegas worked OK it seems like.
JIM
Thread Starter
Instructor
Joined: May 2004
Posts: 187
Likes: 0
From: Fort Drum New York
Thanks, i'll take a look at it when I get back down there. (The car is in my parents garage in Austin). I'm in the Army 
up here at Ft. Drum NY. It has a saginaw 4 speed now, with a bell housing that is not corvette specific. (I need help finding the correct part on that one) I want to make it origional looking and get a super T10 with the 81' correct shifter. as long as the motor isnt itself bad, im happy. with 110,000 on the clock, its good and broken in. And still runs well too. Thanks for the advice.
Robert
up here at Ft. Drum NY. It has a saginaw 4 speed now, with a bell housing that is not corvette specific. (I need help finding the correct part on that one) I want to make it origional looking and get a super T10 with the 81' correct shifter. as long as the motor isnt itself bad, im happy. with 110,000 on the clock, its good and broken in. And still runs well too. Thanks for the advice. Robert
