Bearings instead of thrust washers?


Ain’t no feeling like Oldsmobling!
Feb 10, 2008
Too much time bench racing!! Just out of curiosity, TH400 trans, if you machined every surface that has a thrust washer for a bearing, what if anything could you expect to see on a time slip? Ever done a back to back test on a dyno? I would think it would have to be worth something, as much as GM pinches every penny they wouldn’t have spent all the time and effort to machine the 4L80 instead of thrust washers. I’m sure it was more of a fuel economy concern over performance, but reduced friction saves fuel just as easily as reduces ET. Just curious if there is anything scientific to prove or disprove

dank GN

BlackArts Automotive (661)993-8277
Jan 11, 2009
SoCal the high desert
They have kits that you just replace all the thrust plastic shims with toringston bearings. I have done it and don’t think it’s worth anything on the time slip. It’s more of making the trans last longer at higher power levels.


Texas, Where are you from
Sep 10, 2002
as long as you maintain the fluid wedge in the unit the bearing isn't helping. But when the forces push the fluid out and parts make contact, a roller or ball sure helps. This is why the fluid and internal pressures are so important. And new bushings and setting the clearances really make a difference in how long an overhaul goes.
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