The Stovebolt Site Forums The Shop Area Driveline 1951 3/4T Pinion Rebuild stiff

Rebuilding the differential. Replaced all pinion bearings. Inner, outer bearings, spacer and race all as a new set, used a 20T press, gently, bearings properly seated.. All part numbers match those removed. I put back together as came apart. And matched the drawings on the Shop Manual "Rear Axle 4-15" page. Followed assembly instructions. Once all assembled, and not installed in carrier, shaft did not rotate easily.

Seemed like the Retainer, pinion bearing and oil seal (item 5) was dragging on the inner cone slightly.

I installed in the differential carrier, with bolds, cannot get the retainer to seat against the carrier, and pinion will not rotate at all.

So when I removed there were 2 shims, put them both back, have not even gotten to measuring backlash with the ring gear installed. No shop manual info about checking length, or shimming before checking backlash.

Seems I need a thicker spacer (5)?

Ideas rear end experts

If this still is an HO52 Eaton axle, last I looked those pinion bearings were somewhere between unobtainable and very expensive NOS. It bears being careful as it seems you are doing.

It sounds like the bearing preload is too tight. Could you have mixed up the spacer no.5 with spacer no.7? No. 7 will set the bearing preload. No. 5 provides a seat for the u-joint yoke and tightening that nut should have no effect on preload. This is a much better setup than the crush sleeve used on various light duty axles like the open driveline half-ton and car ones.

Did you give the end of the pinion shaft a good whack with a brass drift to release the stress on the assembly after pressing? If this was an NOS bearing I wonder if the spacer got switched with another one along the way somewhere. Did you keep track not to use the original spacer but use the new one that came with the new bearing? It probably would not be a good idea to add a shim on top of no. 7 as one wants to avoid shimming under a bearing but you may have to do that to reduce preload. Too much preload will make a high speed bearing like this run hot. In some applications, rather than preload, there is a couple thousanths clearance. However, just as a reference, the straddle-mounted tapered rollers in my 6231 Spicer gearbox specify 2-3 thousanths preload. Like a pinion bearing it typically turns up to 3500-4000 RPM.You can't directly measure that but the torque required to turn the assembled shaft will give you a good indication of preload.

Shims, no. 13 will locate the pinion depth. Assuming you are replacing only the bearings, you should use the same shims. You'll have to use a dial indicator to set the backlash when you get to that point. Check the gear pattern anyway. One I got from a boneyard had WAY too much backlash and I reduced it to spec. but I was afraid it would howl but it didn't and the pattern was correct so apparently the gears hadn't worn into the loose pattern.

The bearings were not difficult to get, I have them, I installed them.

Yes, seems too much preload. Used spacer that came with bearing. Odd thing was, when I tore apart, the spacer was not there.

I didn't bother loading the differential in the carrier as I know this is wrong, no sense checking backlash when you cannot turn the pinion.

Thanks

Mikeybakken , you wrote that when you tore apart "the spacer was not there", if you are referring to the #7 spacer that is seemingly not possible. The spacer , #7, that comes with the pinion bearing is what establishes the preload for that bearing. When you press the first bearing on, the inner race bottoms out against the shoulder on the pinion shaft, when you place #8 and #7 on the shaft and then press #6 onto the shaft the inner race of the second bearing seats against the spacer which seats against the inner race of the first bearing.......you should be able to hold the outside of the pinion bearing and turn the pinion shaft fairly freely......if not, there is a problem with the preload. I would suggest you remove the nut and pinion shaft washer , and the flange , the #5 spacer and check the ease of rotation without the flange installed. If it rotates freely without the flange you've narrowed it down to the flange/ seal assembly. The number five spacer allows the flange to press against the inner race of the bearing #6 and the retainer #4 should move back and forth on the flange seal surface with little to no interference. Send me a PM with an email address and I'll send you the pdf file "Servicing the New 3/4 and One-ton Truck Rear Axles". Its one heck of a lot better than the Shop Manual, in my opinion......

Hmm... If I understand what you've said, OP, it appears you've solved your problem. You forgot to put the preload spacer in.

I have done stuff like that and once lost a spacer that I couldn't find a replacement for. In that case the adjustments for preload was done by changing the shims under the bearing cups (races) and there was only one size spacer. I tried making one out of a piece of cast iron pipe but it was too soft. In the end, I had to adjust preload by torquing the yoke-retaining nut and estimating the torque required to turn that bearing along with the other bearings when in neutral. It wasn't ideal as the yoke worked slightly on the splines, gradually loosening the preload as the yoke wore into another piece-of-pipe spacer, even with a castle nut and cotter pin but it was a piece of logging equipment and was easy to adjust then needed.

The #7 spacer was missing. I noted that when I disassembled because it didn't match the manual drawing. It was not lost. A bit of a moot point as the new kit had the spacer and it was installed. Yes it is supposed to be there, I assembled it with a new set including the spacer, as per manual, so understand how it is assembled. Pressing the second bearing is not necessary as does not have tight tolerances.

It does spin freely when completely assembled. It does not spin when the assembly is installed in the carrier.

It's been nearly a week since the last post in this thread. If you still haven't solved the problem, here's a few more comments on oddball situations:

If all's well with the pinion assembly when out of the carrier with the yoke and nut on and at least somewhat tight, I would suspect some bearing bore mis-alignment. I have run into that where the outer race bores on a stradle-mounted pair of tapered rollers were not square with each other. This resulted in repeated bearing failures for no apparent reason. I no longer remember what tipped me off but I ended up having the case bored square and sleeved to take the outer race. This was on an expensive, heavy-duty transmission and so was worth doing.

Maybe somebody left the preload spacer out for a reason and used the castle nut to set the preload. Had one of the pinion bearings failed or did you replace all the bearings for some other reason? Maybe the bore for the pinion-nose bearing isn't concentric with the pinion bearing bore or possibly the pinion-bearing bore isn't square with the differential-bearing saddles, which will try to make the nose bearing off center with it's bore and cause a bind of the pinion bearing if it's preloaded. Try installing the pinion assembly without the nose bearing and observe if that bearing inner mount is concentric with the outer bearing bore. Also note if the pinion turns freely with the nose bearing off and if the pinion retainer now sits in position properly.