Okay, the roads got icy a few days ago and it got bad enough I needed 4wd, everything was good until it got on pavement and I let off the gas. It made a horrible noise at any speed and any gear. I have 3 31s and a 265/75, all bald and of different brands, i know you're not supposed to use 4wd on pavement but I'm just wondering if anybody else has this problem, and it's also impossible to get out of 4wd without unlocking the hubs after it's been on pavement.

 

Does the noise go away in 2wd?

 

Yes, the noise will start in 4wd and get quieter and slower as I hit the brakes

 

You might find you can shift out of 4 wheel Drive if you put in reverse and roll back several feet, while gently pushing forward on the 2wd/4wd selector. (From 4HI to 2HI)
If this is the case then your issue is most likely a difference in ratios between your front and rear axles, due to your tires being mismatched in size. One of my toyotas has two different differential ratios! front and back and I need to back up to get it out of 4wd. This ones not my daily driver and the 4wd is fine for getting unstuck, pulling my boat etc. but I don't drive around in 4wd. Hope this helps.

 

Tire diameter! If all tires were brand new you would be ok even on dry pavement for a short time but the slightest diffence in tire size seems to put opposing pressure on gears & driveline. I have tires of all the same size but usually different brands and different diameters from wear if only 1/8 inch and I can't even get out of 4X4 in dirt sometimes, its as if the transfer case locks up. Usually I can get out of 4X4 like said backing, turning, rocking or unlocking hubs which is probably the best thing to do. If tires are actually different sizes I wouldn't go into 4X4 at all myself, even on sand. The noise from what you said might be the tires slipping on pavement kinda like pealing out theres constant wear on tires never mind driveline fighting against each other, let off the gas and seems like you applied the brakes, not a good thing IMO....

 

It slips out really easy on dirt, the noise is definitely the t case and driveline, we greased the driveshafts and filled fluids and checked for shavings. We also tightened the rear output flange. I tried to roll backward and that didn't help, I'll get it binded and then get in some gravel to see if that's the problem.

 

Why did you tighten the rear output? Was it loose? Remove the rear drive shaft and drive around some in 4hi, that will help isolate the problem

 

its the different tire sizes, more then likely. I always have to back up to disengage transfer boxes. its been the case on everyone we have ever had, with manual transfer case.

if nothing else you need a matching set of tires all the same tread and tire pressure to properly troubleshoot your noise problems.