12 bolt differential pinion seal replacement

[David67]

67 c10, 292, 12 bolt rear differential. The pinion shaft seal is leaking badly, but our manual doesn't really say how to torque the nut after replacment of the seal. (Bearing MAY need replacing...not sure yet).

Any guidance/tips would be hugely appreciated. How critical is the nut torque? Some other blog said something about pinion bearing wearing out if not done properly, but no help on just what "properly" was.

Thanks in advance.

David

[Wrenchbender Ret]

I could answer this but there are really good tips in todays post "cause of leaky pinion seal.

[425HP409]

If you are going to simply replace the pinion seal, you must follow these instructions to keep from under or over tightening the pinion nut which will cause pinion bearing or ring and pinion failure.

1. Mark the pinion nut's position before loosening and removing it
2. Install new seal
3. Install and tighten nut to the "exact point" that it was before you loosened it

Check and fill with oil and you should be good to go.

[StingRay]

Make sure to use a speedy sleeve on the yoke!. A seal itself won't do much if the yoke is worn. Like said mark the nut and pinion. Count the number of exposed threads and count the number of turns coming off. Put the nut back on exactly the same as it was and then just a hair past and I do mean a hair. There is a crush sleeve in there and the nut must be as tight as it was before or it can cause a world of problems and you don't want it too tight or the pinion preload will be too tight. It's all really pretty simple.

[lilred67]

i replaced the one on my '70 the other day. i got the seal at NAPA and i did not like it at all. it leaked worse than the original. picked one up at GM and it worked great.

[USAF]

Does anyone know the procedure to set the preload? I've searched and searched and the only thing I can find that may be close to correct is to tighten the pre-load bolt until you feel resistance and then back it off 1/12th turn and tighten the lock nut. Does anyone know if this is the correct procedure? I need to change my pinion seal and the more I read the more hesitant I am of doing this.

[Jrainman]

The correct way is to also change the crush sleeve along with the pinion seal to the correct inch pounds (NOT FooT Pounds ) 14- 19 inch pounds is the corrct Preload you are looking for , if you have new bearing the inch pounds on the preload would be around 14-16 inch pound if you are not changing the bearing you would be closer to the 19 inch pounds depending on bearing wear , The issue is that a inch pound torque wrench/rachet is a very expensive tool to buy , Marking the pinion nut is a hit or miss way to solve your issue because you are doing this with out replacing the old crush sleeve witch is what holds the preload ,when the crush sleeve fails the seal fails also the bearing eventualy fails . but if you are just going to replace the seal Ratech 116k is the kit I reccomend to buy , there are youtube videos on this subject that will help you also.

[USAF]

Thank you Jrainman,
I do have a very good inch pounds torque wrench that I use to build my Honda GX gold dredge motors (connecting rod torque). I have searched for "HO52 Pinion Seal" and "Eaton Pinion Seal" but can't find anything specific to the HO52 or 72 since that aspect is the same for both I believe. My "guess" is to remove the driveshaft, remove the 5 bolts that hold the yoke in, remove the yoke, remove the seal and felt, replace the seal/felt, replace the yoke, replace the flange & 5 bolts, replace the yoke & driveshaft, set the preload to 19 inch pounds and set the lock nut? If there is not an old felt in place, I'm wondering if I should use a new felt as I ordered a new seal & felt.

Other places I have read state to screw in the preload bolt until you feel resistance and the back it off 1/12th turn.

I'll definitely make a video to replace the seal and set the preload and post it to YouTube.

Thanks again Jrainman.

[howell57]

I have heard of marking nut, but aren't they suppose to be torqued to 250 foot pounds? Just took my two piece out and the nut was no way at 250, barely had to use any force to get if off.

[howell57]

There is a 12 bolt car and a 12 bolt truck seal and they are different.

[Robert Crandall]

I changed the seals on a 12-bolt differential from a 1966 C10. These postings seem to be near what I am doing, so I will add to it instead of starting a new one.

I could not get the pinion nut loose. The differential was out of the truck, so I took to my favorite tire shop, and their impact got the nut off.

It is now back together, but I cannot get the nut tight enough. I'm working from a GM Light Duty Truck Service Manual for 1977. The steps in that manual before disassembly match those shown by poster 425HP409 in post #3. I did those three steps. Additionally, the manual states to measure the rotating torque before disassembly then exceed that measurement by 1 to 5, but no more than 5, inch-lbs after reassembly. My before and after measurements are 2 inch-lbs. I have never done this before, but those measurements seem very negligible.

My problem is that I cannot get the nut tight enough to match my marks. The nut needs to turn an additional 1/8 inch to line up with the marks on the pinion and on the shaft. I took it to my favorite machine shop, and they could not get it to tighten further. I now have it under the truck with the parking brake set. A breaker bar with pipe, and my impact, do not move it.

Is there a recommendation for how to get that last 1/8 inch of rotation? Also, is a 2 inch lbs initial torque reading reasonable?

Thanks!

[Rust_never_sleeps]

I bookmarked this video because it made sense to me, but I haven't yet done it, so ymmv:

https://www.youtube.com/watch?v=AqezIqSz5Ww

[pjmoreland]

Originally Posted by Robert Crandall

I changed the seals on a 12-bolt differential from a 1966 C10. These postings seem to be near what I am doing, so I will add to it instead of starting a new one.

I could not get the pinion nut loose. The differential was out of the truck, so I took to my favorite tire shop, and their impact got the nut off.

It is now back together, but I cannot get the nut tight enough. I'm working from a GM Light Duty Truck Service Manual for 1977. The steps in that manual before disassembly match those shown by poster 425HP409 in post #3. I did those three steps. Additionally, the manual states to measure the rotating torque before disassembly then exceed that measurement by 1 to 5, but no more than 5, inch-lbs after reassembly. My before and after measurements are 2 inch-lbs. I have never done this before, but those measurements seem very negligible.

My problem is that I cannot get the nut tight enough to match my marks. The nut needs to turn an additional 1/8 inch to line up with the marks on the pinion and on the shaft. I took it to my favorite machine shop, and they could not get it to tighten further. I now have it under the truck with the parking brake set. A breaker bar with pipe, and my impact, do not move it.

Is there a recommendation for how to get that last 1/8 inch of rotation? Also, is a 2 inch lbs initial torque reading reasonable?

Thanks!

I ran into this situation once. The nut was bottoming out on the pinion step at the base of the threads before the preload got to where it needed to be. You can see if this is your issue by removing the nut and washer and then look inside where the washer was and see if the pinion yoke is flush with the step in the pinion. If this is the case, then one solution would be to remove the pinion yoke and install a shim between the front pinion bearing and the yoke. This would allow the pinion yoke to push the bearing in more before the nut bottoms out.

[Wrenchbender Ret]

This is a real old thread.
We are talking about 2 different rear ends & getting very confusing.
The HO52 & 72 are from 3/4 & 1 ton trucks. The c10 1/2 ton trucks have a lighter duty rear end with 12 bolt cover. Witch one do we have here?
They are completely different procedures to replace the pinion seal.

George

[Robert Crandall]

Thank you, Rust_never_sleeps, for the video. That example worked well. His marks lined up after impacting. My result is different from his. He makes no mention of torque measuring, which is different from the manual.

Thank you, pjmoreland, for your advice. I will look at that if I have to.

Thank you, Wrenchbender Ret. The original poster describes a 67 C10. His photo shows a short bed, so I presumed his differential to be the same as mine from a 66 C10. I apologize if I have that wrong. 2010 is far beyond 1966 and 1967, so I presume a fix for those vehicles in 2010 would be valid for 2024.

[Robert Crandall]

I've kept the advice offered by poster pjmoreland in mind. I have the differential back in the truck, so it is securely held, and the parking brake will keep it from rotating while I mess with the nut, so I'm thinking about taking the pinion off to look for the condition that pjmoreland describes.

I took no further than the pinion off to change the seal. Could the bearing have backed out just from having the pinion off? There was a lot of impact banging done.

To confirm, was the time that it happened to you just a remove the pinion to change the seal operation?

Thanks!