4x4 issue

[kaiwren986]

Hi all, been sneaking around the forum. Ive done a search but cant find any answers to my specific problem.

When I put it in 4lo I get binding at while just creeping a few feet havnt tried to use it anywhere. I can feel the drivers side rear suspension go up, then when I put it in 2hi I get a clunk and the truck levels back out.

While in 4hi I get a light grinding noise and a gentle rocking forward and back motion, again havnt moved it more than a few feet, and very very slowly.

Any ideas? Im going to flush the front and rear diffs and also the transfer case.

Its a 99 Tahoe with autotrac. I just bought it been slowly nursing it back to health This is the last mechanical thing it needs.

Thanks in advance!

 

[taylorjm]

Rocking motion? Did you look at all your u-joints in the front end? I definitely wouldn't use it at any speed with that going on. Sounds like it's going to throw a drive shaft or something in the front end! If it was me, I'd take it to a shop and put it on a lift and check it all out in the front and see what's going on.

 

[kaiwren986]

The u-joints seem pretty good it only has 112k miles on them, and none of them in 4x4 mode(was a chicago police department vehicle) but I'll put it on the lift and check it out.

 

[SunlitComet]

By any chance did someone change a axle gear set ratio and not do the other at the same time?

 

[kaiwren986]

its highly possible. the things Ive found done to this poor truck are astonishing

As Ive said I have binding after creeping 2-3 feet I dont even really get a full tire rotation. That would probably be the gearing wouldnt it? I know its got a g80 in the back. Any way to check the fronts without ripping it apart?

 

[SunlitComet]

not definitively. However I have a plan.

Place the vehicle on a frame lift put a whit chalk mark of some sort near the valve core. while on that lift put it in 4lo and in first gear only and let the brakes off. assuming no brake binding all wheels should be about the same rpm. if the fronts turn at different speeds then rears then there is an obvious gearing issue. Don't do it to long tho as you front cv shafts are angled more then usual and can accelerate the wear and stress.

 

[kaiwren986]

Good idea I'll have to take it to get it on a lift this weekend and will post back my findings. Thanks Sunlitcomet