We just bought a new Sure-Grip for the Challenger.

[SteveSS]

The '71 Challenger has a 408 Stroker with an 833 4-speed. It came with an open 2.76 open diff. We somehow happened onto a Sure-Grip 3.91 and ran that for a while. It blew up eventually and we went back to the open. That started leaking really bad so I bit the bullet and ordered a new/rebuilt Sure-Grip with 3.55 gears. I remembered a guy in Arizona was rebuilding these so I tracked him down. His name is Tom Hild in Lake Havasu, AZ. It was $1450 plus $150 shipping. He builds these neat little crates for shipping. I wired money today and he just sent me a picture of the unit completed and packed in its container. None of these diffs are cheap but I thought this guy was reasonable.

I'll let you know how it feels and sounds once it's in.