: 70 DeVille rear end leak

Jeff R
06-23-13, 03:54 PM
Have a 70 Coupe Deville with a rear end leak. It appears to be from the front seal where the u-joint is. Is this replaceable externally or does it all have to come off?

Also, if it all has to come off, that isn't in my budget now to have done(I'm getting too old to do it in the driveway with just jackstands) can anything be done to help the seal for now? Thinking of some type of seal helper that those autopart stores sell to fix leaking seals.


06-23-13, 07:36 PM
I believe the answer is yes. I haven't worked on a 70 rear differential (my 70 Eldo is front wheel drive). There should be a pinion seal that can be removed with a seal puller and a new one pressed/tapped in. You will need to remove the U-joint and [most likely] the pinion yoke.

I have a 1970 Cadillac shop manual at home. I'll check when I get back and see if I can't give you some more specific info.


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06-23-13, 10:03 PM

Ok, this actually looks more involved than rear differentials I've replaced the pinion oil seal on. Here are the pages from the shop manual that cover it...

Jeff R
06-23-13, 10:40 PM
Yah I saw those in the manual. It is a little more involved than I wanted. I had just hoped that there was an easier repair.
I am wondering if those additives that swell seals would work and if so, which one-- an engine or transmission or power steering seal rejuvenators would work. I'm just talking about a temporary fix until I can swing having it done.

06-24-13, 10:21 PM
That, I have no knowledge about. Is it leaking rapidly? Or more of a slow drip? Meaning, can you just keep topping it off with fluid?

It's actually pretty awesome that it's possible to remove the pinion gear without taking the entire differential out. To change the pinion bearings on my 1999 Jeep Grand Cherokee, I have to take out the axles, differential and everything prior to being able to get the pinion out. However, it is much easier to change the seal.

Jeff R
06-28-13, 11:46 PM
It is certainly a leak but not so bad that I can't drive it. I can keep topping it off with fluid. It is just a PITA to keep sliding a drip pan under it when I park. It will leave a stain about the size of a dinner plate under the rear end when parked. It won't do it when sitting tho, or just after a short drive. Only when it is warmed up. I have cleaned the vent.

06-30-13, 02:10 AM
Hi Jeff,

I had the same leak last year. I bought the rear pinion seal from az for under $10 I think. I went to my great (I use for my modern car) mechanic and he said he'd do it for 1hrs labor ($80) but I had to make an appt in a few weeks and I didn't wanna wait.

Went to another guy who is across the street. He's good but I wouldn't have him do major work. More like brakes and front ends etc.

He charged me $50 to install. It's easy if you have a lift.

Also if you get it done make sure they add a small bottle of gm gear fluid additive to the gear oil. It mentions special fluid in the service manual but wasn't specific.

When I picked my Daisy up the rear end whined. I thought the guy screwed it up. I went back and we took a ride. He said oh I forgot to put the additive in. 10 mins later no whine. A year later and the differential is fine.

Jeff R
06-30-13, 06:08 PM
Sounds like it would not be too bad but my problem is that I don't have a lift. Probably worth having someone do it.