Have a 67 Cutlass with the 12 bolt non-posi rear axle. Was taken all apart during the restoration, all looked good inside, to the best of my recollection, I replaced the axle seals as well as the pinion bearing and seal. Now after only a few miles of driving, I have a pinion seal leak that is getting worse, so obviously have done something wrong. Looked up install on bearing and seal, they went in fine, but iffy on the preload. Looked up some info online, but either was incomplete or I did not comprehend it properly. All that being said, I will have to get back into it and could use some advice in user friendly terms if possible. I'm a decent mechanic with most things, just don't have a great understanding of the preload process. Thanks.

 

Since you said that you are having problems w/ the pinion seal, I'll assume the preload question is on the pinion bearing preload (not the carrier bearings preload).

Once you've established the correct carrier and pinion shims to achieve a good gear mesh pattern, verify the yoke surface where the seal rides is nice and smooth. Install a fresh seal and lube it with a bit of oil. Then install the pinion, bearings and yoke w/ a crush sleeve and begin to torque the pinion nut. As this pinion nut is torqued, the crush sleeve will begin to compress until the point where you have "proper preload" on the pinion bearings. This "proper preload" is determined by measuring the amount of torque it takes to rotate the pinion. I think it is between 15-20 in-lbs, so you'll need to use a very small pointer-style torque wrench to measure this rotational torque. This tool will likely have a small 1/4" drive, so you'll need a couple of adapters and a socket to engage the pinion nut when measuring this pinion rotational torque. As long as this torque is below the target value, you are OK, and you can tighten the pinion nut a bit more, then recheck the rotational torque. If you go over the target value, you have too much preload and will have to dis-assemble and try again with a NEW crush sleeve, so patience is a virtue here. It took me 2 crush sleeves to get it right.

This is probably the most difficult part of re-assembling the rear axle, since in order to tighten the pinion nut, you'll have to apply a very high amount of torque to the nut while holding the yoke to keep it from spinning. I clamped my yoke between some press-plates from my shop press that were sandwiched between 2 pieces of plywood to keep the yoke in contact with the heavy steel plates, then I "hit" the pinion nut with an impact wrench for as short of a burst as I could, then re-checked the rotational torque between each hit w/ the impact.

I should mention that, establishing the "proper preload" is also required when adjusting the pinion and carrier shims to obtain the optimum gear mesh pattern. However, this is done without the crush sleeve installed and in turn requires a relatively tiny amount of torque on the pinion nut to obtain the "proper preload" without the crush sleeve. What the crush sleeve does during final assembly is provides the clamping force to the inner bearing races to keep them from shifting around when under the heavy load of driving. Crushing it just the right amount results in some of this clamping force to be transferred to the outer races and housing to obtain the bearing preload.

Hope this helps, and good luck.

 

Yes, it is the pinion bearing I was talking about. The carrier bearings were not changed as I saw no reason to. Actually, as I am remembering, the pinion bearing looked good as well, I just thought I should change it as I had it apart and was changing the seal. Here is a point; I don't remember changing the crush sleeve. I reinstalled it as it was and tightened everything down on some advice I got or something I read being a novice at differentials at the time. Unit makes no noise or has any other issues other than the leak. Could it be I got a bad seal or more likely damaged it in reassembly? It will be a few days before I can get it on the lift and check it out. Thanks.

 

I would have left the pinion bearing alone but that is water under the bridge. I have done multiple pinion seals and not replaced the bearings. In the dealership I worked at we were careful to tighten the nut just enough to take the play out. Sometimes the seals just fail, sometimes something gets caught in them an takes them out.

 

Sometimes the inner seal lip spring will pop off when tapping the new seal in...Once this is dislodged the seal will not do its job. Another failing factor is you did not lube the lip with grease before installing the yoke. DRY seal will burn up fast
Next did the seal get installed straight / square in the housing. If it is cocked a bit ...it will leak. It there any in out play on the pinion shaft? any in out or up down play will cause the seal to fail
pinions only movement is twisting.

Hope these help.

Jim
J D Race

 

Indeed, any play in the pinion shaft is an indication of loss of bearing preload and will allow the pinion / yoke to squirm around, which will kill a seal in short order too.

 

Ok, I was able to pull the seal and yoke and yes the spring had dislodged from the seal. I reassembled the parts and although I did not actually "set" the preload, I tried to return it to where it was. Finally had the chance to take it out today and I accelerate then when I take my foot off the gas, I get a horrible whine from what I guess is the rear axle, since there was no noise like this before. Accelerate again and it goes away. Let up at speed and it's back. I am going to guess that I need to go ahead and get a new seal and crush sleeve and try this again with the advice I have gathered here. Would this be a correct assumption? Do I need to replace the pinion bearing as well? Thanks.

 

Sounds like you did niot crush the sleeve all the way
WAS there any in out play on the pinion?

IF the gears were not noisy before you changed the seal...then it is your preload or lack of preload etc on the pinion nut. The gear has to be climbing the ring meshing incorrectly on each other.

J D Race
Jim

 

That was my thought given some time to think about it. The second time I installed the yoke, I may not have tightened it up as much as the first and the sleeve is loose causing the noise. No matter, I have ordered a new sleeve and seal and will repair it properly with the knowledge I have now.

 

The shifting whine noise (none on acceleration, lots on deceleration) is a sure sign that the pinion bearings have no preload and is allowing the pinion to move around.

You didn't mention if the leak was fixed. If so, you might be able to just tighten the pinion/yoke nut a bit to regain the pinion bearing preload (however, you won't be able to verify "proper" preload without pulling the carrier so that you can measure the torque it takes to rotate the pinion by itself). At this point, you don't have alot to lose. Worst case is that your pinion bearings will suffer a shorter life due to some damage encountered by a short amount of driving w/o preload and will have to be replaced.

If the leak continues, then I'd pull it all apart, install new pinion bearings and seal, new crush sleeve and get the pinion bearing preload set right.

 

That is what I did this morning, sounds fine now. But I have the parts to fix it properly if it tanks. Or when I buy that posi unit.

 

Great to hear.