When I make very tight low speed turns in my C-1500 with the G80 rear axle, I sometimes notice a kind of juddering from the rear. Doesn't happen very often, but it is noticeable. I changed the diff oil to 75W-90 synthetic, but there was no change.

My question is whether this is normal.

 

No, that's not normal. Is it the original rear axle? Low speed shuddering on tight turns is typical of limited-slip/positraction diffs due to clutch chatter, but that doesn't happen in the G80 locker.

 

I am not sure the rear diff is the original. I do have the build sheet, which specifies G80, but that doesn't mean that's what's still in the truck. All I know for sure is that it has a 10 bolt cover, and behaves like a limited slip diff. There's s slight whine from the axle under power at speeds over 50 mph, which I find odd for an axle with only 85,000 miles. Could be a set up problem, not sure.

Any tips on making a positive ID of the unit in the truck? No tags on any of the bolts holding the cover in place.

 

Jack up the rear axle so both rear wheels are off the ground with the vehicle in park. If you spin one wheel, the other wheel should spin in the opposite direction with relative ease. That shows an open diff, which is how a properly-functioning G80 should behave.

With a limited slip, and the vehicle in park, it should be difficult/impossible to turn a wheel.

 

Interesting. The build sheet, where it lists the G80, says it is a limited slip. Now I am totally confused...

 

g80 is a type of limited slip, terminology can be a pain in situations like these, the only definite way to know is to pull the cover and look

 

I guess you're right. Over the years, internals could have been swapped out, so who knows what it is now. I can tell by the tach, that the original 3.73 ratio is still there.

BTW, this light-duty 1/2 ton with the 350 vortec likes to get up and go when you stomp the loud pedal.