Differential pinion seal replacement

[Jack's 47]

I removed my driveshaft to replace the u-joint, and thought I would replace the differential pinion seal and differential gasket since there is a slow leak. Does anyone know of a guide or instructions on how to do so? I've done a lot of my own work on cars over the years, but never touched a differential before. I removed all the bolts to the carrier(?) and it still won't come off.

 

My truck is a 1947 Dodge 1/2 ton.

[Merle Coggins]

In order to pull the whole diff assembly you first would need to remove the axle shafts. However, none of that is necessary to replace the pinion shaft seal.

 

Since you already have the driveshaft off, you now need to remove the input flange on the diff. Remove the nut and slide the drive flange off the shaft. You may need to use a puller. You can then use your seal remover of choice to remove the old seal. Install a new seal and reassemble. You may also want to inspect the seal surface on the drive flange. You may need to put a Speedi-Sleeve on it. Upon reassembly you'll need to apply a certain amount of torque on the pinion nut. I don't have that spec handy at the moment. 

 

While you're at it, I would also advice that you check/clean the axle breather. If the axle can't breath properly it can build up pressure that will cause seal leakage.

[Jack's 47]

5 minutes ago, Merle Coggins said:

In order to pull the whole diff assembly you first would need to remove the axle shafts. However, none of that is necessary to replace the pinion shaft seal.

 

Since you already have the driveshaft off, you now need to remove the input flange on the diff. Remove the nut and slide the drive flange off the shaft. You may need to use a puller. You can then use your seal remover of choice to remove the old seal. Install a new seal and reassemble. You may also want to inspect the seal surface on the drive flange. You may need to put a Speedi-Sleeve on it. Upon reassembly you'll need to apply a certain amount of torque on the pinion nut. I don't have that spec handy at the moment.  

 

While you're at it, I would also advice that you check/clean the axle breather. If the axle can't breath properly it can build up pressure that will cause seal leakage. 

 

Great, thanks for all the help! I'm guessing the axle breather is on the top of the differential? What does it look like?

 

Also, are you saying that in order to replace the gasket I have to pull the whole diff assembly?

[Merle Coggins]

I missed the part about the gasket. If it’s leaking between the diff housing and the axle housing then you will need to pull out the diff. Are there gaskets available for that? I usually use RTV or Permetex Anerobic Gasket Maker, which seals and hardens well for that type of mating surfaces. 

 

For that you will need to pull the brake drums, disconnect the brake lines, and remove the brake assemblies. Pay attention to the shims behind the brake backing plates. Then you can pull out the axle shafts. You will need pullers for the brake drums and the axle shafts. Once the axle shafts are out you can then remove the diff assembly. 

 

The axle breather is incorporated into the bolt that holds the brake line splitter Tee to the top of the axle tube to the left of the diff. 

[59bisquik]

Another thing to note if doing the pinion seal besides the possible need for a speedi sleeve is different vendors offer different types of seals for that. Some have leather like stock and others have the newer neoprene style which I prefer. But of course material is your choice.

[Jack's 47]

Okay, since I'm doing all of this in my dirt driveway, I think I'll hold off on brake and shaft removal until I have a garage. 

 

Does anyone know the pinion nut torque setting? It was very loose when I removed it.

[Dodgeb4ya]

180 lbs. minimum torque. 

[MBF]

I think I would  put a staked mark on the face of the pintion nut and the pinion threads to return the nut to the existing tightness and not change the pinion bearing preload.   That was advised on another post on this forum years ago.   Mike

[Jack's 47]

1 minute ago, MBFowler said:

I think I would  put a staked mark on the face of the pintion nut and the pinion threads to return the nut to the existing tightness and not change the pinion bearing preload.   That was advised on another post on this forum years ago.   Mike

 

The pinion was not preloaded. The nut came off by hand.

[Dodgeb4ya]

9 minutes ago, MBFowler said:

I think I would  put a staked mark on the face of the pinion nut and the pinion threads to return the nut to the existing tightness and not change the pinion bearing preload.   That was advised on another post on this forum years ago.   Mike

Before I take the pinion nuts off I mark them carefully.... nut, flange and pinion .... I re-assemble the flange and nut right back like they were.... nut just a hair tighter than the mark... cotter pin still needs to be in same slot. This is really important on crush sleeve type which lucky our old MoPars don't have.

If the nut and flange are loose upon removal... something is wearing out and reference marks on the nut mean nothing....there is more investigation needed.. like are the pinion bearings worn.

[JBNeal]

My 1st differential rebuild was because of a leaky gasket and seal on the '48.  When I removed the carrier, inspection of the bearings found galling on the rollers, evidently a byproduct of the truck being parked for decades...after spending a few $$$ on bearing sets and a weekend on figuring out how to do the adjustments in the manual, that rear axle really tightened up and ran smooth...unfortunately, I did not know about speedi-sleeves back in the 90s nor the importance of gasket sealant, so the oil still seeps, but at a drastically slower rate

[Don Coatney]

[woodrow]

this is a great explanation of how to do the diff and pinion seal.  I am currently replacing all brake lines, cleaning out all cylinders and replacing the brake fluid.  so seeing that both seals are leaking  I guess this is a good time to do them.  2 things I have to ask tho. what is a speedy sleeve? and how do the axles pull out before the diff comes apart.  are they kept in by the axle but or something else? and is it ok to use gasket maker on the diff? thanks for any and all info. this forum is an immense help with working on my P15.

Edited March 20, 2019 by woodrow
damn spell check dont know how to spell

[Merle Coggins]

The axle shafts are held in place by the brake backing plates. It sounds like you already have the brakes disassembled, so now just remove the backing plates too. You'll need to rig up a puller or slide hammer to pull the axle shafts out. The bearing cup is a tight fit into the housing. I've made spacers to go between the axle housing flange and the inside of the brake drum and use the axle nut to pull the axles out. You may need a few different length spacers to get the job done. I've also heard of putting the drum and nut on loose and using the drum as a slide hammer of sorts.

Once the axle shafts are out you can replace the outer seals, and you can also pull the diff now (if needed).

Gasket Maker is good for the diff mount surface. I prefer the Permetex Anaerobic Gasket Makers/Flange Sealers for that application

[woodrow]

That all makes good sense about how to pull the axles.  and yes, I have got the entire brake system stripped so I'm pretty much there.  I'm wondering tho.  every part I get for my car, other than a few brake lines and other generic parts, I have to get shipped from out of country.  its adding up by now.  if my outer seals are good before pulling the axles, will they be good if I dont change them out and just reinstall the axles? I know the seals are probably cheap themselves but the shipping is not cheap. 

[Merle Coggins]

Where are you located, woodrow?

[woodrow]

Newfoundland, Canada

[Merle Coggins]

You don't have good parts supply stores there? Most seals can be cross referenced to modern numbers readily available from local vendors. I got mine from Napa.

[Frank Elder]

Princess Auto?

 

[woodrow]

16 hours ago, Merle Coggins said:

You don't have good parts supply stores there? Most seals can be cross referenced to modern numbers readily available from local vendors. I got mine from Napa.

I tried napa.  while they do carry some brake hardware they could not find the pinion seal.  however, after seeing that you got yours there I may just call another store.  I may have been unlucky enough to get a newbie behind the counter.  thx for the help and I will update. 

Frank; I find Princess Auto , here anyways, doesn't have anything like that. More of either surplus items, hydraulics, and welding.  

 

[Merle Coggins]

Look up the OEM part numbers and have them cross reference the numbers. You can even use the napaonline web site to do it yourself. In their search bar at the top of the page type in the OEM part number and then select Cross Reference in the search category. See what comes up. 

[Dozerman51]

Is the 180 Lbs Ft. Pounds or Inch pounds? I’m in the same boat. I forgot to punch mark the nut and pinion when removing the oil seal in my 8.75” 4 pinion third member in my WC-12. Thanks for any help.

[Merle Coggins]

If you’re talking about the pinion nut 180 inch lbs would be pretty light torque. 180 ft lbs sound better. 

[ozzmonaut]

I hate to bring back an old thread, but this is where I am at. I believe my pinion bearing is shot. With the rear end off the ground and car running in reverse, the rear end squeaks where the pinion comes through the housing. When driving in reverse (wheels on the ground), it makes terrible clacking noises. Sounds fine going forward. 

I am fairly sure that with it jacked up, the weight being off of the bearing is what quiets it. Seal is not leaking and diff is still full of oil.

 

Anyways, I have replaced the rear axle bearings, as I thought the noise was coming from the rear driver side. So now I have the axles back out and am about to disconnect the driveshaft and pull the carrier. Does anyone have the correct part numbers for the pinion seal, bearing, and carrier gasket? The pinion seal looks easy enough to find. The carrier gasket appears to be fel-pro RDS 4290, but I am not absolutely certain. The bearing... I am having some real trouble tracking down.

 

Thanks for any help you can give me.

[Merle Coggins]

I just use a good RTV sealant instead of a carrier mounting gasket. As for the seal and bearings... you can usually find identification numbers stamped into the parts that can be used by a good parts counter person to cross reference them. Or, if you have a parts book for your car you can often cross reference the OEM part number.