I ran into a situation recently where my '93 F250 bogged down in some sand and had to be winched out. What's odd is this: I had driven for several miles with no problem. I started to make a sweeping right hand turn and as I did, I could feel the truck bogging down. I tried to give it more throttle to keep my momentum but it was hopeless pretty quick. My immediate thought was that the tranny or t-case had popped out of gear, but that wasn't the case. I got out and immediately noticed that my LF tire had really dug in. The RF looked to have dug a little, but not much. I assume that's because the front is an open diff. Oddly though - the back tires never rotated a bit - after winching out, there was a large hole where the LF was, a small hole where the RF was, but the rear tires had only sunk in a couple inches - about the same as it was at cruising speed. And - once I was out of the hole I was able to drive off like nothing ever happened. That was several weeks ago and although not a daily driver, I've probably put a couple hundred miles on it and driven it down the street in 4H and 4L with no obvious issues.

This has me puzzled. I thought the t-case always split power to the front and rear - so even with open diffs I should have had at least one tire on each axle spinning, right? Is my understanding wrong? Can anyone help me understand what was happening?

 

It still drives in 2wd?

 

The front and rear are hard locked together in 4wd. When making a sharp turn something has to give in order to make the turn. The inside front wheel will bind up as it will need to make fewer rounds in the turn. On dirt and gravel you will be able to feel the front end hopping as the wheels fight against each other. This is very hard on the chain in the transfer case, and all other parts involved.

Even in snow I try to shift into 2wd when making a turn. If that is not possible due to road conditions, I will turn the wheels and use the throttle to break the rear tires loose and spin the truck in the direction I want to go.

 

To my surprise, yep. When I was stuck, I couldn't even get it into 2H and thought it was toast. But I later remembered that sometimes I need to roll the truck just a little then try again to get the t-case to engage. I assume(d) was just to get the gears to mesh better, as it's happened for sure with both 2H and 4H. I drove several miles out in 4H, then shifted to 2H without issue once back on solid ground. No issues since, and I've shifted into 4H and 4L a couple times just driving down my street.

 

the fronts were probably in softer material, and the rears were in harder material. so the fronts dug in, and the rears just spun without digging.

 

Actually, the rears definitely did not spin. The tires that spun (the fronts) threw sand everywhere, while the rears did not. I could even see the tread pattern all around where the rears sat. I"m confident that they did not ever spin. I just can't come up with any mechanical explanation for it.