I’ve had my 91 F150 with auto 4x4 for about 7years and the 4x4 has never worked. It was never really a priority since I don’t have a need to use it but yesterday I decided to install a new transfer case motor and now I have 4x4.

My question is around how its supposed to function. 2wd to 4hi works fine, once 4hi is on it switches to 4lo just fine however doing the reverse doesn’t seem right. Going from 4lo back to 4hi the dash lights represent the change but if i put it in drive it acts like its in neutral. And if I turn 4lo off then 4hi off to go back to 2wd it switches over but its pretty loud transfer. Something doesnt seem right but just looking for insight since its never worked I dont really have anything to compare it to.

 

No experience with the auto shift on that vintage, but found things worked easier with the manual shift between Hi and Lo range with a very slight bit of vehicle roll, either direction (FWD or REV). IMO, slight clunking isn't objectionable, major clunking suggests here something may be in a bind.