Aside from a ballooned convertor and/or an incorrectly installed convertor into the tranny pump, is there anything else that can lead to major thrust bearing wear. Picked up a used 76 wagon motor to find out the thrust bearing had worn more than .040. Otherwise bores were fine, little taper, no scratches, and radial wear on bearings was fine and visually there didn't appear to be any core shift. Planning on using just the block for a hot build and was wondering if there were any factory block abnormalities in 76 that could also cause excessive thrust wear.
I think crank end play is what you need to look for. I think the tolerance is like .003- .006". Not sure. If that's out of whack you'll get some thrust bearing wear.
Perhaps the thrust bearing was not installed properly. It must be loaded towards the front of the engine before the cap is torqued. This is done by shoving the crankshaft towards the rear of the engine, and then forcing it towards the front of the engine. Then the caps are torqued with the crankshaft forced forward. Failure to do this could result in bearing shells that aren't lined up, so one shell takes all the pressure, and the "ridge" between the upper and lower shell will interfere with the oil film, and if the thrust bearing isn't pushed forward against the block bulkhead, pressure will flex the bearing and lead to fatigue failure.
The engine was factory assembled and the wear on both halves was equal The only thing I could think of causing thrust wear is a force pushing the crank forward like a ballooned convertor or a convertor not aligned up and installed deep enough into the transmission.
material problem On the otherhand , you ve got me thinking about the bearing material being problematic. Could have been a flaw in the backing steel of the thrust side of the bearing. Anyone ever have this experience ?
This problem could have ben caused by a bad conveter that was repaced before you got the car .Just a thought. Maby they only drove the car dow hill.
The earley switch plate conveters would cause excessiev thrust bearing wear. Or maby they only ran the car backwords at a very high speed. RonJ
First I've known about the switch-pitch converters causing thrust bearing wear--More details, please. (I have a SP trans and converter, from a '65, waiting to be rebuilt and installed, so now you know why I'm concerned!)
Stupid trrust bearing statements Jim & Schirkey I started something that I should have not,sying stupid things about this thrust bearing. The statement about the switch plate converter I got from one of the old Buick mechanics at the Buick dealership that I do their computer networking for. I will ask him for some more details and get back to you RonJ
Line Bore We tried a different crank (dead straight) with a new set of mains and there was binding, meaning the line bore is out. (Yet the radial wear on the old mains looked normal and the old crank spun freely) I did not realize the line bore or a combination of a bent crank and line bore could cause the crank to ride forward against the thrust surface cause this excessive amount of wear. Time to line hone the block Check ut the pic on the crank thrust face wear.
When I was working in a engine shop we had a many rebuilt chevy engines come back with wiped out thrust bearings. Every one of them was in a 3/4 or 1 ton truck or suburban with TH400. Funny thing is the original motor that came out had no thrust wear. I came up with a little mod to the bearing to get more oil to the rear side of the thrust and used alot of assy lube on the bearing and the problem seemed to go away. I know its not Buick related but seems odd that it was always a big truck with a TH400 and extra trans cooler. The boss did some research and was told that the trans was trying to push the converter out the front but I don't remember the fix for it. Tom
If using an auto transmission, the oil going into the torque convertor MUST be able to get out. If your confident that the convertor oil in/out passages are correct ( many times they are not, especially aftermarket) then start looking into restrictions in the cooler lines, cooler itself, or the lube circuit in the transmission. Something as small as removing the orificed cup plug from the main shaft on the THM 400 can make a big difference in thrust bearing loads! By the way, increasing the cooler line size from 5/16" to 3/8" can make a difference too and add about 300 rpm of stall. Just some things to consider. Jay
