Diff Pinion Seal Won't Stop Leaking

This question is about my 01 RAM 2500 with Cummins 5.9L engine. It has a Dana 80 rear end. I drove it about 120 miles and when I got home parked it in the driveway. The next morning, I noticed a puddle of diff fluid under it about the size of a quarter and there was a small patch of fluid flung on the underside of the bed. So I took it to a local mechanic who has done work for me before. He changed the seal on it and then called and told me that it still leaked just a little bit and he wanted to put another seal on it. So he kept it a few days and then called and said the new seal leaks too and that I needed a repair sleeve. He couldn't find a repair sleeve locally, so I ordered one off of Rock Auto and he installed it. Yesterday he tells me that it is fixed and to come and get it.

So I pick it up at his shop and drove it to the market 4 miles away. When I get out, I notice that the tailgate and bumper are covered in oil. I look under the truck, and the whole underside is coated in oil (spare tire, leaf springs, bottom side of goose neck hitch, etc.). It looks like the underside was sprayed with a power washer filled with diff fluid. Now he tells me that the seal he installed was bad and he is going to install a new one. I asked him how bad the pinion was damaged because he needed the sleeve. He said it didn't have any damage on it not even a scratch. He thought it needed the sleeve to make the seal take.

He also mentioned that it may needed a new pinion if the new seal doesn't work. If the old pinion wasn't damaged (no scratches or marks), why would it need a new pinion?

This seemed like a very simple 30 minute fix and now he has had the truck over 15 days. What is he doing wrong? Is it just a case of bad luck with the seals?

Maybe he should find a different brand.

Using a pry bar on the faces and maybe it's gouged? If numerous new seals don't work it's something other than the seal.

Peep6543 said:

Using a pry bar on the faces and maybe it's gouged? If numerous new seals don't work it's something other than the seal.

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Yes that's what I am trying to find out. What could it be other than a seal?

Probably wear or corrosion on the shaft, bushing or both. Sleeve kit is a cheap fix that doesn't always work, but generally worth a shot vs a rear end rebuild. Should be easy to see with the seal out. Shaft is part of the pinion gear so if the shaft is worn or pitted the pinion has to be changed.

Is there slack, up and down or side to side? Meaning the pinion bearing is bad.