I've only owned my truck about a month so I'm still familiarizing myself and I don't have a detailed history of servicing of the 4x4. Engaging into 4Hi while moving forward seems to work just fine, but when in reverse it is almost as thought the parking brake is on. There is a lot of resistance. When I then disengage 4wd and move forward it also struggles for a bit and then I hear a noticeable clank as it comes out of 4wd. I'm just wondering if you have any suggestions of where to begin with my diagnosis....

 

Welcome. Why don't you help us out by telling us what year it is, what engine and transmission.

 

Sorry, thought it would show in my signature. 1992 SR5, V6, 5spd, 4x4.

 

Try it off pavement

Resistance is normal in 4wd. The front and rear tires are trying to move at different speeds, mostly because the front is heavier and or tire pressure is lower in the front or rear. Try putting about 5psi more in the front. And off coarse not usin 4wd unless your in slippery terrain. An empty pickup theres not enough weight to compress the rear tires at all. Compressed tires smaller circumference, blah blah blah....

 

OK, that makes sense. Generally I wouldn't be using 4x4 on pavement, particularly in reverse, I just wanted to test it out....