Rockola, I have rebuilt a few of these transfer cases, I don’t see anything inside these that will blow up because I test it on jack stands. The speed sensors will notice the front wheels and rear are not going the same speed and set a code that is easily cleared once work is done.
Sometimes a noise can’t be isolated without a test like this.
Running the truck in gear on jack stands does cause the front diff to work the spider gears unusually hard and that makes odd noises, the CV shafts hanging low with the control arms fully down is not good for them either so I think I will repeat the test with the front driveline removed. If the rear end and transfer case end up quiet after this test I know it is the Front differential but I really hope not. I have never rebuilt one of the front diffs and do not want to learn that one.
Had one with 4.10 gears, was thinking of switching to 3.42 gears for better MPG. I installed a rear diff with 3.42’s and for this test removed the front driveshaft and drove it about 300 miles. MPG was basically the same and the vehicle felt slow off the line after running the 4.10 ratio fso I reinstalled the 4.10 gears. Had to clear the codes of course but no other issues. For my use I really liked the 4.10 gear ratio and would get one again.
A fried Viscous Coupling does not lock up. The fluid overheats and loses it's ability to resist shear, and thus do anything. The VC acts to limit speed differences between the front and the rear. The VC is the money part in the AWD unit. But it is absolutely your BW AWD unit to do with what you want.
This is why they they make horrible sounds when ran on the lift. Those sounds arent happy sounds either.
Front and rear diffs are ridiculously easy to rebuild, its the setup that is an art and if not done properly the diff will live a very short life. Ive seen them get destroyed just going across town after an improper setup.
I distinctly remember a guy rolling up in his 5.0 in the late 90s and he couldnt slam on the gas no more. One of his buddies did him a "solid" and regeared the diff for him and before he made it across town there was less than 50% of the teeth left. There was actually "neutral" spots in the diff because of it. The grinding noise was one of those you never forget.
