I am looking for any ideas, or fixes to the following.

First off... I have a 2005 Blazer 4wd ( has the push button 2Hi, 4Lo,4Hi, 4 auto.)

Ill list my problems. I dont know if any are related or if they are completely different from each other.

1. At about 65 + mph the vehicle shakes. And gets worse the faster you go, to a point where you think the wheels will fall off. It has been Road Force Balance by a chevy Dealer and did not help any. I did notice one of the rear rims looks like it has stress cracks or spider webbing on the surface.

2. At oil changes I always check the front and rear diff fluid. The back is always low and needs to be filled. (never seen a leak puddle or anything though) The front is usually fine, but this time it is also low. (does this take the same 80w-90 oil or something special?- the books are kinda vague on this)

So first off, are these two issues related to each other? Any ideas what is the underlining problem is.
Do I need new wheels and or tires to correct the vibrations (if so thats too bad cause the tread still looks really good)
Would the virbations casue the diff to loose fliud? Or is this a separate issue.

Any help or ideas on what/how to trouble shoot this would be appreciated.

 

any suggestions on how to diagnose these problems?

 

Patience man, patience!

Cracks in your rims are BAD! I don't know why someone would balance or even drive on rims that were cracked. That is quite possibly the reason for the shake, but if it isn't and the wheels/tires have been ruled out, then you have to start searching through the rest of the drivetrain.

Both front and rear axles take 80w90 (or 75w90 synthetic - my vote).