I thought the regular pickup trucks got a standard TH400/3L80. Wasn't there also a 3L80HD(TH475)? I thought those were only installed on motor homes? I think they have a brake mechanism on the tailhousing. I don't know what the difference would be, maybe straight cut gears? I was reading a few threads on the Jaguar forums, and some of those guys are very knowledgeable on the TH400/4L80e. Maybe do some reading over there. Performancetruck.net has a lot of information on the subject as well.