89 Lesabre blowing transmission output seals

[CatmanFS]

So, this 89 buick keeps blowing trans output seals to the cv axle. It did it once about a week ago, and i unfortunately took it to a shop and watched the guy do it, was easy looking repair, and got charged 150. Anyway, a week later the same thing is happening, leak from the output shaft seal.

These cars are still very similar to the Bonnevilles as far as engine and basic design is concerned, and I was looking at the do-it-yourself shift kit for the 4T60-HD and was wondering if there is a similar method that can be performed that would help with this thing's transmission problems.

Any input would be appreciated.

Replaced filter and fluid keeps leaking out, front brakes are also needing to be replaced, they're kinda broken, but cant see how messed up brakes could cause a trans leak.

[clm2112]

Did the mechanic do anything to the surface of the axle where the seal rides? I mean, a new seal on a rusty or pitted shaft isn't going to last very long. Also if it was installed dry, it will also self-destruct before the fluid from the transmission works it way into it. That's pretty much the case with any seal on a spinning shaft.

I'd take it back and let them fix it gratis.