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Rear pinion nut

2K views 16 replies 4 participants last post by  DZA 
#1 ·
Hi,

I have leaky rear end on a 1976 GMC C1500. I knew just enough, from youtube, to get in trouble and do things wrong. The leak remained. I marked the nut but I didn't count threads or rotations. I'm now leaking a lot more fluid. The first time around, I put the nut back on with a 2' breaker bar. Now I'm reading/hearing about needing closer to 150-250 ft/lb on a torque wrench.

Today, when I took the thing apart, I noticed that the pinion nut wasn't tight at all. It probably took less than 1/8 turn with no effort at all to start loosening the nut. It took maybe another turn before I could start turning the nut with my hand with the wrench sticking out straight.

Something else I noticed was that the yolk took 0 effort to remove. I'm watching youtube videos of guys using pullers to remove the yolk or flange.

Simple logic is telling me that the leak is from the backside of the yolk not being pressed up against the seal well enough. The attached photo shows where the leak is coming from. It's not from around the outside of the seal. I had gray RTV on that.

Other things to note, maybe, are that when I pulled the seal off (today), as the oil was pouring out, the bearings floated forward and the pinion gear was loose. I pushed the bearings back to where they were sitting and the pinion gear wasn't moving at all. Is all of that normal?

So the problem is that I don't want to pay a shop to do it right, and I don't want to break my rear end. Is there a solution?

Any thoughts on how to put it back together where it's not going to leak and be good enough for driving around?

Do I need an torque wrench? How many lbs? How many turns on the nut, etc? I've googled around but there is a lot going on that I don't have the knowledge for.

I appreciate the help!
 

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#2 ·
I need to copy this on my computer so that I don't have to type it out over and over.

Get a new pinion nut.

Clean the splines inside the yoke (not yolk) and wipe off the pinion shaft. Clean the threads on the pinion shaft. Smear some RTV sealant into the splines INSIDE THE YOKE, not on the shaft. Smear some grease on the rubber lip of the seal. Put the yoke on the pinion shaft. Put red Locktite on the threads of the shaft. Put the NEW nut on and torque it to 150 foot pounds. Put the drive shaft back in and you are finished.

Yes, everything that you described is normal. The outer pinion bearing will sometimes be loose and move around when the yoke is removed.

If you do all of this and you still have a leak then you probably have a bad pinion bearing. Be sure to check the yoke and seal to be sure that they fit correctly. I installed a late model seal on an early model 8.5 GM 10 bolt and it leaked very bad. I didn't check it before I installed it.
 
#5 ·
Do we not simply tighten the nut until we attain around 18 in/pounds for used bearings or around 22 inch pounds for new bearings?

I personally just tighten until the bearings "feel good" by using an impact gun. Setting the bearing preload as mentioned above is what the books say, but no GM tech I know sets up rearends using an inch/pound torque wrench for setting bearing preload.

Its a bit tougher for just replacing the pinion seal because the ring gear and carrier is not removed from the case.

Curious, what's the theory behind needing a new nut?

peace
Hog
 
#6 ·
The nut is a lock nut. When you use it it becomes loose. A new nut will be tight and not back off as easily as a used nut.

I only use the 150 pound torque for a rear end that is assembled when the crush spacer will not be replaced. When setting up a rear end with a new crush spacer the bearing preload must be measured and set to the correct amount.
 
#10 ·
Since I did not see it stated, you need to carefully inspect the yoke where the seal makes contact for a wear groove. Any groove in that area on the yoke will make for a leak even when a new seal is installed.

As BGH states, with the yoke in hand, slide the new seal onto the yoke where it would normally ride. If it fits tightly with resistance, it should be the right seal. If it flops around on the yoke-wrong seal!

I guess we are not putting a new crush sleeve in?
 
#11 ·
One member mentioned RTV on the inside of the yolk. Would that help eliminate any loose/groove issues?

Should I just replace the yolk just in case?

I have no plans to replace the crush sleeve. That would involve taking the rear end apart, correct? I have watched a few videos on it. Opening up the rear means potential of me doing something else wrong putting it back together ha.
 
#16 · (Edited)
Ok.

Also, hopefully lastly, will you please look at this attachment? It looks like a little less than 1/8" of a gap between the lip of the seal and the rear. Is this about right? I used a homemade wooden block with a hole in it to hit the seal on fairly evenly. Everything look good?

Edit: The gray is gray RTV in case that isn't obvious in the photo.

Thanks.
 

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