how do i know when the diferental is going out on my 90' chevy blazer
on 1990 Chevrolet Blazer

my chevy blazer is making a clanking sound any time it is in gear.
checked the universal joints and they seem to be fine. the clanking is getting loader and loader. it is not just once but repeated.

Asked by for the 1990 Chevrolet Blazer
The vechicle will buck in and out and the engine will actually jump. You can observe this with vechicle on a lift or all four corners secured on jack stands. Do not go under vechicle but observe from side, have someone put vechicle in drive and press on gas and you will see it "buck violently" and make the noise. The shaft going to the rear wheels may not turn at all if this is a 4wheel drive transfer case issue and that severe. If so, you will need to replace the transfer case.