742 pinion bearing preload ?

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mderoy340

mderoy340

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I'm working on a 742 I bought locally. The pinion seal was shot so I marked the pinion nut for reference before removal. Pinion also had .010 end play prior to removal and 2 inch lbs rotation drag.
The FSM has no mention of end play spec so I am assuming it should be zero and rotation inch lb spec sets the bearing preload. Is that correct?

It had 3 shims under the forward bearing 2 .020 and 1 .009
I removed 1 .020 shim and now have zero end play 2 inch lb rotation.
Should I remove another shim and recheck?
I don't have a shim kit but can always buy if needed.
Thanks for any info.
 
You are correct in your assumption that the rotation inch lb spec sets bearing pre-load. Shim to what ever it takes to get rotational pre-load.

Good luck.
 
I've taken apart some differentials with loose pinion bearings (very little to no preload) but I don't think I've ever seen one that had .010" end play. That would make me wonder about the condition of the bearings.
 
Thank you for answering my preload ?
Everything looks to be visually ok but I wanted to be clear in my mind on the pinion bearing preload before checking wear pattern and setting backlash.
Thanks again.
 
................I would think u need new bearings, even though u took out the free play u have moved the pinion farther away from the crown gear so now ur gears will be meshing in a different spot meaning u changed the pattern from where it was............kim..........
 
More details would help to give you the correct info. Was the pinion nut loose or torqued down before you took it apart? Was the gear set quiet before you took it apart? Did you check to see what back lash you had before taking it apart?
 
SGBARRACUDA said:
More details would help to give you the correct info. Was the pinion nut loose or torqued down before you took it apart? Was the gear set quiet before you took it apart? Did you check to see what back lash you had before taking it apart?
Click to expand...

This rear was bought locally so running condition is unknown. The pinion seal was an OEM leather seal.
The pinion nut was tight before removal, backlash was .008, and wear pattern looked good
I reinspected the front bearing and found wear marks on the cage. At that point I decided to disassemble and do a complete rebuild. The forward bearing cup had a slight wave looking wear pattern up top, the aft pinion and carrier bearings are good.

Sometimes buying this old stuff doesn't work out but I got it cheap enough to rebuild without breaking the bank.
 
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