Front Differential Issues

[Waldo]

Howdy All,

I have been chasing a problem for a while now with my 96 4.3 Manual k1500. Around 45 mph I start hearing an intermittent grinding noise from the front end that has a grind about twice every second. the grind increases with speed, slows down with breaks, and does not matter what gear I am in. The truck has newer tires and entirely new front suspension (including wheel bearings and cv axels). the issue continues whether my front drive shaft is attached or detached. I have a few ideas of what it could be:

The 4 wheel drive actuator could be incorrect or broken. I reused the same one from my old frame (I did a frame swap) since the new frame had an electric push actuator instead of the manual one.

The front differential could have a bad bearing. It is more likely this one since the old frame had an unknown amount of milage on it. If this is the case, would it be better to rebuild the old one, or just throw a whole used/new one into it? I think there is a leak on the passenger side seal anyways...

Any ideas or insight would be greatly appreciated.

 

[Schurkey]

Drain the gear lube, look for debris in the oil.

The differential doesn't hold much lube. If there's a leak, there may not be enough gear lube in the housing.

Verify that the brake rotors aren't rubbing on the dust shields.

 

[GrimsterGMC]

Drain the gear lube, look for debris in the oil.

The differential doesn't hold much lube. If there's a leak, there may not be enough gear lube in the housing.

Verify that the brake rotors aren't rubbing on the dust shields.

I second the rotors rubbing on the backing plates, I chased that noise for ages before jacking the front up and spinning a tire to discover it was something so simple and fixed it.

 

[Waldo]

I drained the front diff and filled it with fresh oil and it did not seem to solve the issue. I think the dust shields should be pretty good as there is no noise when i move the wheels with the front up. The odd part about the issue is that the noise only occurs at speeds over 40ish which makes it hard to test parts, but thank you for the advice!