These transmissions need a D4 ATF and the transmission filter needs to be changed at around 15k. This seems to be working great for us. Also yes try to get an external transmission cooler but not a very large one as the tranny pump is not so great. Yes the main reason is better cooling but it also removes that dangerous cooler in the ticking time bomb called a radiator. If it ever overheats it will burn the tranny oil and take engine and transmission with it as well... Learned this the hard way
