Made two left turns within 15 seconds and heard some noises and had some bucking with it? The truck has 58,000 on it and a nelson 89 tune. I this the front diff?

 

wheel bearing. u joint, loose bed, bad shock, Cat.

where did it sound like it was coming from?

 

It was hard to tell i was on the phone. I would have to say though it came from the rear?

 

If there was bucking, might be the rear diff...do you have a G80 locker?

 

It's the 14 bolt with 3:73 from the factory.

 

But do you have a G80 locker (factory locker)?
In your glove box look for the RPO code G80.

 

Yes it has the code G80 in the glove box. On the window sticker it states heavy duty diff.

 

Could be the G80 going out.
They are notorious for breaking. If your hard on it around corners especially. They last a while in a straight line, but if you spin em alot and roast em around corners they don't last what so ever.
I don't know what kind of fluid those use.. anyone know? adding a little more might help it out for a bit.

 

It could also be the locker acting normally, locking and unlocking, if it locks up on pavement then your are going to get some bucking, and they clunk when the lock and unlock

 

I agree with you. I took it in for some new fluid's for a peice of mind! The truck has 59,000 on it and i haven't done that yet!