I have just purchased a new differential off a place that was closing for 300 bucks...CHEAP. It is a 4.10`s, posi. Now, i have a 91 chevy caprice with a 305 TBI, and was wondering how bad it's going to be on gas, and how bad is it going to affect my top speed. I have a 700R4 as a tranny, and don't know if it's going to put up with it. Now from my knowledge, this car will probably go down the highway @ 100km'h, revving up to 3500-4500 RPMs. I did't install the diff yet, but i know that the one i have now is a 2.56 granny ratio, one wheel burnin' diff. It will probably make a world of difference at low speeds, but at top ed, it will probably be a drag on gas. Any suggestions or comments would be appreciated. Thanks