Hey guys so I recently put a 3.5" rough country lift on my 97 grand Cherokee and it started making this whining sound from the tcase I changed the fluid in both diffs also checked for metal shavings got nothing. I'm stumped right now I've heard wheel bearings and pinion angles can be a problem but I need more brainstorming

 

Without more info on what lift you have it is hard to tell. If you put a 3.5" lift on without a SYE, the. You probably have u-joints screaming especially if everything in the driveline is still stock (original).

Do you have adjustable control arms?
Install SYE (I don't even know if they need it)?
Is it all the time or only at a certain speed range?
Does it change when going up a steep or down a steep?
Does it happen when you are under hard acceleration?
Did you take the driveshaft off when installing and did you install it the same orientation?

You may also get more feedback in the correct forum.

 

Welcome to CF!

An SYE or slip yoke eliminator, removes the sliding part of the t/case output shaft and moves it into the driveshaft itself. This requires replacing the driveshaft with one that has this feature.

The lift changed the angle of the driveshaft enough to put tremendous stress on the t/case output bearing. As this guy said, you may not need one because, if I remember correctly, my 97 ZJ had a flange-mount output shaft. It was a 4.0. If you have a V8, it might have a sliding yoke.

 

Is your front driveshaft a cv or u joint ?If its a cv that could be your problem.

 

no I do not have adj control arms and yes it starts happening as soon as I acceleration and no I did not take the driveshaft out during the install

 

I have a 4.0

 

It's a u joint

 

You could try this: take off your front driveshaft, see if it does it. If it still does it, put the shaft back on and take off the rear driveshaft, drive in 4hi, see if it does it.

 

Okay I will try it this weekend thanks

 

pinion angles are key. the double cardon joint 'balances' itself, but the angles on the shaft front and back need to be correct, I can't recall the whole science of it but google is your friend. In other words from what I recall, the u joint at the back of the shaft's angle dictates what the front u joint angle is ..someone with better knowledge chime in pls

 

Unfortunately, there isn't much you can do about the pinion angle unless you rotate the differential and that's just about impossible to do and keep the caster angle right. For the rear shaft, you can drop the t/case to reduce the angle slightly, but that just makes the front worse. The t/case drop is used mostly on TJs where the rear shaft is very short.

 

You say you didn't remove the front shaft during the install? I wonder if the sliding section is jammed from being overextended. That would put stress on the t/case output bearing.

 

I think you can add a double or cv joint at the rear and it will offset it