I have a 97 f150 xlt 4x4 auto 4.6 with 258000 miles and still going except It has a history of the transfer case assembly failing. Actually, I don't use the 4x4 that much so can't figure out why it breaks. Ford dealerships are the only ones that work on my truck but they really can't tell me why it fails. They just say the "yoke" goes bad causing the rear extension housing bearing to fail causing other things to fail. I have had the rear drive shaft assy balanced so many times so it's not that. The yoke has been replaced about five times since new.
I bought the truck new in 97 and after three months of driving the yoke went bad.....this was the first component that went bad and it has never stopped.
Basically I'm finally feed up with stock parts so I'm considering a new "ATLAS" TRANSFER CASE ASSEMBLY by advance adapters.
This would mean a new rear drive shaft assemble which is ok if it takes care of the problem once and for all.
Does anyone have any thoughts on this?
Oh yea, I've also had the "clunk" issue as well and I add the teflon grease as a bandaid.

 

Is your truck lifted? Big tires?

 

Tires......lt265/75r16.
Not lifted just stock. Someone suggested I get the truck lazer lined.....suggesting it's been hit or something. It's never been wrecked. Again, 12 weeks after I bought the truck new a "YOKE" went bad. What drives me mad is that no one can tell me what causes the yoke to go bad. I'm thinking it's not getting lubrcated properly.
I'm still looking at the aftermarket transfercase aseembly "ATLAS".