Replacing taper bearings complete necessity for a rebuild?

[Toni]

So I'm working on getting all my parts together for a rebuild and wasn't sure on replacing all the bearings in the case. I don't know much about these taper bearings; is there a way to tell if they should be replaced? At $300 bucks it's not exactly a small cost. I have to at least replace the ones on the intermediate shaft because they got messed up on removal.

Can I simply reset the preload and be done with it? I haven't heard much about people having ruined bearings when they open the case. I want to do a good job on this rebuild so I'm leaning toward spending the dough but if there is really no reason other than being able to say how much money I threw at it then I'd rather not.

Thanks
Antoni

[JackM]

I guess it all depends on your budget. If you see any bluing, fretting, or excessive pitting on the rollers I would replace them. A little more info and pics here:

http://www.jackstransmissions.com/be...c1c4ab731c1349

[Toni]

Thanks for the info.

Forgot about the input shaft bearing as well. Does the same thing go for it? I have currently have two used bearings (mine and my donor tranny), what's the best way to pick the better of the two?

-Antoni

[lawdogg]

The thing about those bearings is that they might come apart on you when you take the bellhousing off and pull the shafts up from the end case. Mine did twice, once the first time I opened it up and the second time after I had repacked them. Then I installed new ones without setting the preload properly and melted my 1-2 shift fork ... it's tricky stuff.

[Toni]

ok, so I'm about to start working on the preloads for the bearings. Do you guys put the original spacers in when using the solder to test for the proper preload or start fresh with no spacers?

-Antoni

[JackM]

If you leave the shims in there when checking it with the solder you may not have enough space to get an accurate reading. I would remove enough shims to get the gap for the race opened up enough so the solder can still be compressed, but not too much.

Jack

[Toni]

Ok after putting in the solder, tightening and pulling all the gears out it looks like the solder was compressed on all of them without any spacers. Now since the spacers are circular I'd have to pull the race all the way out but can I make one cut in the spacer pull the race up a bit and squeeze it in underneath? Any thoughts on doing that? I don't see how it would ever come out...

-Antoni

[JackM]

That will be a little dangerous. The races float when the case is fully warmed up, so they will possibly come apart or loose in the trans if you cut them. If you heat up the case the races should fall or slide out pretty easy.

Jack

[Devilmightcry]

wait. so in our tranny the shims are behind the race and not the bearings?

[phantomrt]

The shims are behind the outer bearing race. I'm not sure what is meant when you say "behind the bearings".

I am an overall inexperienced transmission rebuilder, so stick with Jack's advice over mine. I have replaced taper roller bearings in a few of my own manual transmissions over the years. Every time I did it, replacement of the bearing alone resulted in perfect bearing preload by using the exact same shims that were in there before. My theory is that the bearing manufacturing tolerances are so good that the shims are not there for taking up slack in bearing tolerances, but instead all the tolerance is in the cast aluminum transmission case instead. Or maybe tolerances in the transmission shaft also.

On a 2nd note, how in the world did you mess up one of these bearings just by assembling the transmission? They are made of the hardest metal in the world and no chisel that I have in my tool box can do more than barely scratch them. Maybe they're just cheap chisels.

Next time I do this, I am going to try heating up the aluminum housing to remove the outer race--I've always carefully cut the race with my dremel, and at which point it just falls out.