AWD question

[kazavelli]

Vehicle is a 98 Mountaineer, 5.0 AWD with 126,000 miles.
I recently acquired this vehicle and have been attempting to diagnose and solve a few problems on my own by searching the threads (IAC, MAF, VC) yet now I could use some specific answers to the following issue: In corners, there is a pronounced tendency to act like a 4 wheel drive with lockers. I have read A LOT of posts with the same symptoms and perhaps a failing VC, yet those posts are all accompanied by pops, grinding etc. and mine has ZERO noise issues. So I put the rig on stands and put it in 1st at idle and all four wheels turn as expected. I noticed that the passenger front wheel was moving about 20% slower than the other three, so I attempted to stop the wheel while the others kept turning under power. I was able to do this quite easily with both front tires, one at a time, yet was unable to do it to either rears. I crawled under the rig while everything was turning to check drivelines and TC for noises and such and all seemed rather normal. I then removed the front propshaft to check the CV for binding and it also appeared to move freely. One final check was the tires. There is a 1/32nd tread difference between the fronts and rears and a circumference difference of 3/16th's. I read a post where anything over 1/4 could damage the VC...wondering if that is my issue and nothing more?
My apologies for such a LONG post, yet I wanted to provide as much detail as possible.
Thanks!

 

[ponkotsu]

I think it's pretty normal for the tires to grab and skip turning sharply. I bet it depends a lot on what tires you have. I know mine does it to.

As for being able to rotate the front and not the rear, I suspect that's normal also. I think 70% power goes to rear and 30% to front.

 

[kazavelli]

The turning issue doesnt really bother me, yet I've read several people state that their rigs turn smooth even at full lock doing figure 8's in a parking lot. My rig can do that as well, but it needs extra throttle or else it creeps to a stop. I'm fairly certain that the VC is okay because when I was underneath I could turn the front driveline and the rear driveline didnt move (if the VC failed, they would turn together because the VC was essentially locked, correct?) My big concern is if the tiny difference in tire size has anything to do with it and if I should just get a new set. I dont want to throw money at "possible causes" and the tires are still in great shape, yet if that is the prudent course of action, I will do it!
Thanks again!

 

[FIND]

1/32 difference between the front and rear for the tread can happen between rotations.

3/16" in circumference is about 0.2% of the overall circumference of the tire. It is not enough to cause an issue.

That said, you should rotate your tires if your front is worn down 1/32 more than the rear.

 

[kazavelli]

Yeah, the tire difference seemed negligible but I definitely wanted a second opinion, so thank you for that! That said, is the tight steering feel in sharp corners really something I should just accept?

I did notice a slight whine which starts at 12mph and increases to the point of becoming inaudible by 35mph. It only makes the whine at low throttle inputs...full throttle it isnt present, and when letting off the throttle it instantly dissappears until throttle is reapplied, and again I can only hear it between 12-35mph. While its up on blocks, is it safe to accelerate the wheels to 20mph to attempt to replicate the noise with damaging anything? Just wondering if not having a load on the AWD system is bad for it while everything is spinning that fast?