Rear Axle Seal Replacement

[jlthunder]

I'm trying to determine if I should tackle this job myself or take it to a mechanic.

I removed my right rear brake drum and noticed the pads, drum, and backplate covered with gear oil. I presume I need a new axle seal. This is a 72 GT with the "Square" bolt pattern on the four retaining bolts.

Is this an easy job or should I leave this one to the pros? I have successfully replaced the pionion seal(where the drive shaft enters the rear axle) in about an hour and 1/2 which includes the removal of the torque tube.

[opelenvy]

I am pretty sure it is the same as my '73 GT. I have replaced both with no problem. Ordered them from OGTS. They are pretty much a large O-ring. Take off the wheels, using a socket remove the four bolts using the two holes. From here some folks use a slide hammer. I did not need to. A little tapping and a little pulling by hand and it slid out. Just make sure it is well supported on Jack stands, because you will be pulling it over somewhat. Then just replace the O-ring, lube it with some gear oil, and slide it back in. Make sure it is lined up and lubed up, otherwise it could cut the new O-ring.
Just going from memory here, but I believe that is it.
HTH.

[jlthunder]

Thanks. It is the same axle as the 73. Gil from OGTS said the same thing. O-rings are on order and I should get them by next week. I will be sure to use lots of lube so I don't have to do this twice.

[opelenvy]

I had one that shaved off a thin band all the way around. It leaked, I took it out, reinstalled it and it's fine now.
Good luck.

[kwilford]

Well, I hate to rain on this parade, but when the rear outboard axle seal leaks, it probably isn't the O-ring. Sometimes, but not usually, unless it has been disturbed by removing the axle and the O-ring was damaged when it was re-installed. On the later differential design (post mid-'70), the outboard axle bearing and seal are an integral unit. That is, the seal is part of the bearing. To replace the seal, you have to replace the bearing (new bearings, o-rings, gaskets and retainer rings are available from OGTS).

Can a home handyman do this task? Certainly, with a bit of instruction and a few tools. But a decent service manual (preferably the Factory Service Manual, FSM, for your year of car) is almost mandatory.

But before you go to all this trouble, are you certain that the axle seal is leaking, and it isn't just the rear brake cylinder? If it is the axle seal, here is the procedure (for the later differential design):

1) remove the wheel, pull off the brake drum, and remove the four retaining plate nuts behind the axle hub that holds the backing plate to the differential housing.
2) Using a slide hammer or similar home-built apparatus, impart an outward blow (don't you just love these technical terms!) to the axle hub, which will cause it to slide out. Remove the entire axle.
3) Using a chisel, split and remove the retainer ring, and pull (or press) the old bearing off.
4) slide on (and press on, if tight) the new bearing, with the o-ring groove on the inboard side of the bearing.
5) press on (and this requires a proper hydraulic bearing press, usually available at your local service centre or even garage) the NEW retainer ring, with the shoulder facing the bearing (do NOT try to press the old retainer off and then press it back on, unless you like the idea of the rear axle coming out and smacking the side of your car!)
6) measure the width of the new bearing outer race, and compare it with the recess in the differential, including the thickness of the new gasket (this requires a decent caliper, or better yet a micrometer). You need to add or subtract the thin steel shim rings until the recess is no more than 0.002" deeper than the bearing is wide, and a "crush" fit (where the bearing is thicker than the recess after it has been shimmed up) of up to 0.006" is desirable
7) Install a new O-ring on the bearing, and a new retainer plate gasket. Coat the axle splines with gear oil, and slide and tap it back into place. Replace and torque the retaining plate nuts to 20 lb-ft, replace the drum, and enjoy!

[jlthunder]

Well I got the passenger axle out last night. I was expecting a gush of gear oil, but none came out. Is this correct? The O ring which came off of the bearing seemed very loose.

Normally it is easy to determine if it is brake fluid or gear oil by the smell. Since it is so cold out here in PA, the fluids didn't have any smell.

Upon initial inspection of the axle, prior to removal, the axle, back plate, brake shoes and drums were covered in oil. It could be the wheel cylinders.

I think I will replace the o-ring and new wheel cylinders.

BTW I have the factory manual(2 copies, a nice one for when I'm clean and a grungy one when I'm under the car)

[opelenvy]

You would not get a gush of gear oil if the car is sitting flat. It will all be back in the pumpkin. You can also check the bearing to see if it is tight. It should turn but with absolutely no play.
In response to Keith, my GT never had the axles removed and both at different times started leaking. Simply replacing the O ring worked both times to fix the leak. I'm not saying your wrong, maybe I just got lucky and was able to fix my problem that easily.
If you have the O rings It's easy to replace them, clean everything up w/brake part cleaner and see if that fixes your problem. If you are not able to tell if it is brake fluid or gear fluid, there is a good chance it is the brakes. They are much more suseptable to leaking, especially if not replaced in 30 years!

[jlthunder]

Thanks for the info from all. After I get the parts from OGTS, and put the dash back together(another story), I will take it out for a test ride and get back with the results.

[namba209 (R.I.P.)]

Here'a another trick we used in the USAF for putting in "O" rings. We had some stuff in a can called Technical Petrolatum, a fancy word for commercial grade "Vaseline" This stuff was used anywhere we put in "o" ring seals, air conditioning ducts, hydraulic components, wheel halves, you name it, if there was an "O" ring it got coated with it. One of the neat things about it was it lubricated the ring and it would slide right into the groove, or slide right down the polished surface of a hydraulic piston, We never had to worry about cutting or pinching the ring using it and it was compatible with all aircraft systems, fuel, oil, hydraulics, pneumatics, like I said anywhere we had an "O" ring, it was used. And like my can of anti-sieze compound, I still have a can of this too. HTH.

Ron

[jlthunder]

I was planning to coat the o-ring with wheel bearing grease to aid in the installation Anyone with any objections???

[jeff denton]

My (now) later style rear is going together and I notice there is a paper gasket between the bearing and retainer. I wonder why. Is it necessary?
Seems all it could do is maybe keep corrosion from happening between the bearing and housing.
Oh, Opel experts, any thoughts?

[GTJIM]

My (now) later style rear is going together and I notice there is a paper gasket between the bearing and retainer. I wonder why. Is it necessary?
Seems all it could do is maybe keep corrosion from happening between the bearing and housing.
Oh, Opel experts, any thoughts?

Jeff, The outer ring of the wheel bearing needs to be "nipped" by the backing plate to prevent it rotating in the housing and damaging it. The FSM calls for up to 0.006" of nip with 0.004" ideal. I think you will find the paper gasket is used to set this "nip" and it can be adjusted by using different paper thicknesses.
HTH

[markandson]

The "nip" as you call it I assume is actually a "press" or "crush" fit. The paper ring is NOT used for this. There are steel rings behind the bearing that create this fit. You are supposed to measure the depth of the bearing cavity with a depth gauge with all of the stack in place, that is, the backing plate and the paper gasket. Then you are supposed to measure the thickness of the bearing. Subtract the two and you have the remaining clearance. Put a shim stack in that is .004 to .006 thicker than the clearance, and bolt it up.

[GTJIM]

I know that Opel advises the use of shims on the outer bearing race to set up the correct "crush" as they call it. However; since the paper gaskets are part of the stack that is measured then, in the absence of suitable shims, the gasket thickness can be varried to adjust the "nip" on the outer race.
The point I was trying to illustrate is that the paper gasket has a purpose and simply removing it affects the amount of "nip" on the outer race of the rear wheel bearing.