1994 Chevy Silverado 4 wheel drive problems

I had a similar problem with an S-10 blazer once. I would get a growling or grinding noise from the front axle when I put it into 4-high. What the problem was, is that the shift fork (Part #16 in the diagram above) was worn as if someone had "machined" a groove into the fork. It was caused by excessive wear while the shift fork was riding/pulling against the the sleeve (part #22) to engage the the 4x4 system. It is a fairly straight forward repair, even though you have to seperate the axle tube from the front differential (The axle doesn't have to come all the way off...you just have to move it out of the way to pull out the old shift fork and install the new one.)

More than likely this is something inside the differential, but we need to start with draining the fluid and seeing if you can find any metal and see what the fluid smells like.

If the fluid is black and stinks, then more than likely you have excessive heat in the differntial which is going to cause the bearings to fail.

https://www.2carpros.com/articles/differential-gear-oil-fluid-check

The noise sounds like a bearing issue and the fact that you get movement at higher speeds points to the bearings dragging.

Basically, we need to get this addressed because they could lock up and then you will not have 4WD or it could be locked in place.

Let's run through this and let me know what you find.

Thanks