It could be because the ones I worked on were "ran hard and put away wet" sort of deals out of vehicles that were stock but beat to death. I'm sure the aluminum probably had something to do with it too, and people never checking their fluid level.
When I built the two I did for my Duster, it was back in the mid 1980's or so, and I bought the extension housings new from the dealer. But, I was always under that car doing something, so I checked my fluid all the time. My oldest son and I even drove it to Montana (tunnel ram and all, just changed the rear gear from my 5.13's to a set of 3.55's for the trip), with no problem. That car was a blast, I could shoot myself for even selling it. I must have sold it just before CudaChick moved next door, I don't think she ever saw it, so whenever that was. She'd know, maybe she'll see this and chime in.
