The TH400 does not have the lockup torque converter. So according to what I read if you are using gear-mph-rpm-tire dia formulas, you need to add about 300rpm for a TH400. (Which works out about perfect for the 3.08s I think I must have.) This seems like a bad thing. I primarily use the blazer to tow our camper up to the mountains and hit trails ranging from 1-7 difficulty. I'm wondering if a 700r4 would be better. I'm just wondering if there is an advantage to the slippage in the TH400.