Check inside your glove box on the door. There should be a mini build sheet stuck to it with options your truck has. Somewhere on there you should be able to find IF you have the Trac-loc.
Sounds like EXACTLY what my 97 did. It was making a strange noise only when turning left........It was the dreaded Trac-loc retaining clip problem. One of the clips broke and made a mess of the spider gears. I would go back to that shop and ask them HOW they determined that your differential was A OK if they didn't even pull the cover. I can almost guarantee, when you do pull the diff cover you will find pieces of a broken clip (among other thing) stuck to the magnet lying in the bottom of your housing.

 

Took the truck to a local shop for the differential oil change. Had a good Coupon.

My truck still makes the grinding/crunching noise from the left/rear on left turns.

I'm told the truck has an "OPEN" differential.

So, if it has an OPEN differential that would mean there are NO clutches in the rear differential as there in Limited Slip differentials.

So WHY the noise back there ?

The shop really did not have a good explanation for the noise either. Just speculated possibly an axle bearing starting to go bad and "maybe" even a result of my RF wheel having a crack in it. Really ? Hmm....

 

OK, you've ruled out any trac-lok problems.

It very well could be the axle shaft bearing. When you turn the loads applied to them change considerably.

Changing the bearing isn't difficult. Be sure to replace the seal at the same time. You might consider changing both bearings as you'll have to open the cover to remove the axle, you're more than 1/2 way to changing both.

 

Did they pull the cover and look inside, or just suck as much of the old fluid out as they could and pump new stuff back in? You get what you pay for.

 

Did they spin the wheels in the air with the cover off? Could easily have broken/damaged spiders. But would make noise both directions.

Now that said. You say turning left? The left rear is pushed inwards, the right rear is pulled out. I'd call the right rear bearing suspect.

 

Roger that.

What other methods could one use to determine the condition of an axle bearing ?

 

I really don't know. I dropped the truck off and left it there.

 

I don't know. (See answer above).

Yes, sharp left turn below 25 MPH. Slower you go the louder the noises becomes.

I'm going to try and change out the front shocks before work tomorrow. I'll jack up the rear while I'm out there and do some more inspection work.

Now that I think about it more here, there IS noise from the rear while pulling away from a dead stop going straight ahead. The noise dissipates after 10-15 MPH or so. It's that grinding/crunching type noise like when turning left, but it is NOT near as loud when going straight ahead. ???

Wouldn't broken/damaged spider gears make noise ALL the time ?

 

No, spiders only move while turning. Going straight, they don't move at all, or very minimally.

Not sure where, but somewhere i have a picture of an axle bearing from the camaro. Was in 4 pieces. Didn't make noise, but was leaking gear oil like crazy.

 

You paid a shop to change your Diff oil ?????