Transmission Bearing Question - Replace or Run it?

[1tontoy]

I'm installing a 1HZ input shaft in a late 1980's Aussie H55F with vacuum tcase. I am wondering how to determine if the bearings need to be replaced. The trans was supposed to be rebuilt when I got it, but the 2H input shaft showed very serious wear/damage and would have needed to be replaced. So, I am a bit skeptical.

I've disassembled the gearbox. When the gearbox was fully assembled, I didn't feel any slop/play in the input or output shafts. When I disassembled, the input shaft bearing has some slop/play. The output shaft bearing seems to have a little slop/play. Do brand new input and output shaft main bearings have play/slop? The counter shaft bearings are tight and smooth.

Should I get a complete rebuild kit, or just replace the bearings that have play?

I apologize if this is a dumb question. I suspect most will say to 'replace it while you're in there'. But, I just wanted some background, first.

 

[1tontoy]

Anyone?

 

[TobyB]

Huh- I don't know a ton about the HF55,
but generally, countershaft bearings are the first to go.
So I wonder if maybe the PO did exactly as you're proposing-
replaced the worst and left the rest.
Honestly, there's nothing wrong with that. If a bearing's in good
shape, why replace it? If it's at its wear limit, though-
or, I'd say, 1/2 way there- then most are so cheap that it seems worth it.

I do a cost/time balance in my head on these things-
'OK, it costs me $150 in seals just to open it up, 6 hours to split and pull it,
and the part's $25? I can afford that'
But if it's a $250 part, it's only 1/4 worn, and it's already gone 150k? Meh, I'll
look at it again in another 150k!

It's hard on things you don't work on regularly. There are a few things now that I DO,
and eventually you get a sense of, 'ok, this bearing shows some discoloration, but
I've run them that way before and they were fine for a whole season' or 'yeah, it's just a bit loose now,
but it starts to wear faster after this point.'

Measuring things helps, too, especially if you can find tolerances and limits.
BMW was great about putting that in their manuals... it's nice to have
'hard' numbers, even if they were just the factory's opinion back in 1972!

You just balance your time and your money... and your patience!

not much help, here, huh?

t