1995 GMC JIMMY S-Series 4.3 vortec auto 260,000 and still tickin'.

Replaced rear end from a junk-yard over a year ago. It was a lower mile one in very good condition. Every so often I pull a 16' aluminum boat or 8x8 trailer, and as soon as they are attached and I'm heading down the road I hear a moaning noise coming from the rear end, so anytime I have weight on the tongue, or pull any weight, I'm hearing a low-pitched moaning noise that's cyclid, moaning up and down with the rotation of the drive-train.

Then, when I load my boat from a dock I always pull it out in low gear (shift down to 1st) and hear this god-forsaken growl which sounds like it's coming from the rear end. We pulled off the pumpkin and found everything to be very good. Checked for any slop between gears and the wear patterns are very good. My mechanic seems to think that it's something in the transmission that we think is coming from the rear end. It's only when you put a lot of torque on it, like starting out in 1st gear and punching the gas a bit you also hear it. When you start out in OD, it shifts perectly. It sounds like meshing of gears, but as many times as I've done it, to test it, wouldn't it show something in the gear pattern on the rear diff??

When I bought this vehicle with 140,000 miles on it, the engine looked as though it had been replaced, but when putting it in gear (Drive) it always takes a few seconds to engage, but not in reverse. Any foward gear there's that hesitation to engage, but never in reverse.

Any takers??? It's hard to spot where the actual grind is coming from???

 

Bump!

 

Did you check the u-joint? Mine was doing something very similar to that and would get worse at highway speeds. I never tow anything with it though. When I had my TrueTrac installed, the installer checked out the u-joint and found that two of the caps were completely dry - no grease whatsoever.

Ever since replacing that, it's been as smooth as butter.

 

Thanks Lidberg for your reply!

Come to think of it, we just replaced the rear drive shaft U-Joint that was bad, and put new shocks all around and I think that took care of the howling noise, but there's still a bad grind, growl when I put it in 1st gear and give her gas on a quick start-off, anotherwards when I give her some torque. It also does it when I start off in drive and give it to her, but when I start out in OD, it's fine. It's only under load when I hear this awful meshing of gears. It's probably somethin in my tranny, and the sound is traveling down to the rear end. Any more takers??

 

Or...it could be in your transfer case. That is part of your driveline. Does it get worse or better if you're in 4WD?

 

Did you check the other end of the drive shaft? There's a u-joint on the other end too, or two of them, don't know of the S10's have CV shafts or not.

 

I also had the same problem and it was my rear u-joint. I thought it was my rear. It almost sounded like the rearend was dry--howling like mad! If I was driving and I put it in neutral the howling would go away. Have you tried to do that? just to see what would happen?

 

Maybe you should look at your Pinion Bearings and axle bearings I would check them

 

I had worked on the U-joints while I had posted my first post and it fixed the howling. What I have STILL is a bad grind, growl when I put it in 1st gear and give her gas on a quick start-off, anotherwards when I give her some torque. It also does it when I start off in drive and give it to her, but when I start out in OD, it's fine. It's only under load when I hear this awful meshing of gears. It's probably somethin in my tranny, and the sound is traveling down to the rear end. Any more takers??

I was told by my mechanic that it couldn't be the transfer case, since it is "direct-drive" and that it more than likely would be something in the transmission.

 

Wouldn't hurt to pull the cover see what's going on in there. At the very least for a fluid change.