First off let me say that the previous owner put in a transfer case control module that is questionable... I dont even know if its the right one but until a week ago it was working.. Kinda.. The first problem i had was the front end is always engaged even if its ONLY putting power to the rear wheels, giving me horrible gas mileagle.. Also the AUTO 4wd button'* light would not turn off.. So every time it detects wheel slip it would switch it into 4hi but both 2 hi and 4hi AND the auto 4wd lights (3 of 4 buttons) would be lit up.. Couldnt turn the 4hi and auto buttons off no matter what i do.

Now just in the past week it has been saying service 4wd and that its in 4wd even though it is not.. And getting stuck like that.
Now its stuck with auto and 4hi lights on and i cant get the 2hi light to come on again.. I replaced the switch on the dash and had the transfer case checked for problems but nothing was found wrong.. The mechanic thinks im insane for thinking the transfer case control module is wrong even though i tell him that a NON MECHANIC previous owner installed it. Im about to go balistic and drive this thing into the test range.

Can anyone give me the OE parts number for a 99 2 door AUTO 4wd GMC Jimmy TCCM and also the numbers of other tccms that will work.

You have to take your VIN number to a GM dealer and they can break it down and tell you what the vehicle was built with.

i know thats one way but all mechanics have access to parts number books. Gm will never tell me which trucks have interchangeable tccms and will want 300$ for a part thats 25$ at the scrap yard.