Does anybody know how to tell the difference between a 700R4 and a 4L60? I have a 1991 with a 350/5.7 and RPO code MD8 for the transmission. Everything I can find on it, lists it as 700R4/4L60 which means that is could be either I guess. Did GM start using the 4L60 (not 4L60E) half way through the year? I'm asking because as I understand the 700R4 uses a mechanical Speedo adjustment (gears in the transfer case), and the 4L60 does it all through the VSS. I want to get my speedo functioning right again after going to 33s over the stock 31s. Should I just wait and put taller gears in it? RPO code shows I have 3.43. Will 3.73 be enough or should I go for 4.10? It does more time pulling boats and car trailers than off road these days. I am not a mechanic, and just learn as I do things, so opening something up that I haven't done before makes me a little leary. I don't want to screw it up the first time, and watch my wallet spring a leak to fix my mistake. Desertrat "being drowned in NC"