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Replacing pinion seal on 8.75 rear end

lochenjons

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Bought a 8.75 suregrip to replace the rear end in the ‘70 charger. Replaced axle seals and sealed up the pumpkin with some of the good gasket maker and no leaks from those parts. But the pinion seal seems to be leaking. Is it as simple as impacting the nut off with the yoke assembly, taking the pinion shaft out, getting the seal out with a slide hammer and replacing ? Or has anyone pried the seal out with the shaft in place , seeing a couple different options online and I’ve never really messed with rear diff’s this much before.
 
Depends on the type of rear 741 or 742 case just remove the pinion yoke hammer and chisel the seal out reinstall new seal and your done. 489 case has a crush sleeve for bearing preload and should not be done that way.
 
It’s a 742. Cool, I’ll be doing that Friday when I get home from work thank you
 
Depends on the type of rear 741 or 742 case just remove the pinion yoke hammer and chisel the seal out reinstall new seal and your done. 489 case has a crush sleeve for bearing preload and should not be done that way.
I've heard the same thing. Just pulling the yoke off a 489 case can mess with the gears. HOW DO YOU DO IT ON A 489 CASE?

For lochenjons, I think someone on here posted a picture of a tool he made. It was basically a 2ft.+ bar with a plate on the end that bolted to the yoke. That way, the bar would hit the ground & hold the yoke in place while you impacted the nut off. fyi-I've tried in the past with a breaker bar + cheater bar & even with the car sitting on the ground, the tires turned & I couldn't get the nut off.
 
Just make sure you polish the yokes seal surface before reassembly or you'll be doing it all over again.
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Have had members buy seals at local parts stores leak. If you don't have part number its C/R 18912.
 
It’s a 742. Cool, I’ll be doing that Friday when I get home from work thank you

You have bearing pre-load to consider.

Put a mark on your socket and and a corresponding mark on the yoke, count the number of turns it takes to get the nut off. Use the same number of turns to put it back on plus just a little more (maybe 1/8th turn extra).

You should come in pretty close.

As mentioned clean the surface area on the pinion where the seal rides. LUBE the seal so it doesn't start out dry, the gear oil will then take over.

As an aside, when you get the seal off, inspect the pinion shaft, sometimes there can be a groove worn into the shaft from the seal.
 
The 742 seal is different. Everyone in my area only had the leather seal, which isn't really recommended. I had to get one from Dr Diff.

Used a piece of angle iron with two holes drilled in it. Impact wasn't about to break it loose. Strong bar and a piece of pipe was needed. I even broke my torque wrench when tightening to the 240 lbs torque. I had it in gear, e-brake applied and tires sitting on blocks.
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I couldn't find the seal number from Dr. Diff on the invoice. There are four numbers on the seal that I can't quite make out. No extra metal lip on the new seal.
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Use sealant on the housing where the seal fits and on the pinion shaft splines.
 
Looks like 7216 on the seal. If you look it up you'll mostly find that it's the leather one. Maybe contact Cass at Dr. Diff for the double ridge neoprene one.
 
Looks like 7216 on the seal. If you look it up you'll mostly find that it's the leather one. Maybe contact Cass at Dr. Diff for the double ridge neoprene one.
I bought mine from drdiff but there some on ebay . If you have the seal number C/R 18912 NAPA has them. Guys have bought them from NAPA but they leaked, bet they didn't have a P/N. Tried to buy a hemi front trans seal, no way. Two tries ng called Brewers
 
I bought mine from drdiff but there some on ebay . If you have the seal number C/R 18912 NAPA has them. Guys have bought them from NAPA but they leaked, bet they didn't have a P/N. Tried to buy a hemi front trans seal, no way. Two tries ng called Brewers

That NAPA c/r 18912 looks like a single rib seal. Might be why it leaked. Dr. Diffs has a double rib. Things can't be simple anymore.
 
You have bearing pre-load to consider.

Put a mark on your socket and and a corresponding mark on the yoke, count the number of turns it takes to get the nut off. Use the same number of turns to put it back on plus just a little more (maybe 1/8th turn extra).

You should come in pretty close.

As mentioned clean the surface area on the pinion where the seal rides. LUBE the seal so it doesn't start out dry, the gear oil will then take over.

As an aside, when you get the seal off, inspect the pinion shaft, sometimes there can be a groove worn into the shaft from the seal.
If the differential is a 741 or 742 shims determine the amount of preload on the bearings not pinion nut torque.
 
If the differential is a 741 or 742 shims determine the amount of preload on the bearings not pinion nut torque.

So no need to torque it? Isn't there a rotational torque number? That's why I had in my mind to get it as close as it was.

I actually was thinking in 489 terms with the crush sleeve I guess, lol.
 
If not using a new nut be sure to put some red loctite on the threads and then torque away. The rotational torque is for the pinion with no ring gear/ carrier installed. Lucky for you have the 742 case.
 
So no need to torque it? Isn't there a rotational torque number? That's why I had in my mind to get it as close as it was.

I actually was thinking in 489 terms with the crush sleeve I guess, lol.

There is a rotational torque, very minimal, around 8-10 in/lbs I believe. Those tiny torque wrenches are expensive too. I did both of mine by feel (both 741's) without issue.
 
So no need to torque it? Isn't there a rotational torque number? That's why I had in my mind to get it as close as it was.

I actually was thinking in 489 terms with the crush sleeve I guess, lol.
My service manual says for a 742 case the pinion nut torque to be 240 foot pounds minimum but that would be when rebuilding with new bearings.
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My service manual says for a 742 case the pinion nut torque to be 240 foot pounds minimum but that would be when rebuilding with new bearings.
View attachment 703858

The 742 has shims behind the yoke to set the preload. Removing the yoke to replace the seal you still torque the nut to 240 ft lbs when reassembled.
 
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