About a week ago the drivetrain started to shudder in corners. Somewhat like the cluthes grabbing in the LSD. The problem is not consistent. The clutches don't grab in tight figure 8 loops. Now, there is a moan of sorts coming from the drivetrain. I can also feel the roughness. My first problem would be locating the problem area. I didn't get any movement out of the U-joints. The center bearing moves around in a rubber mount? There is no play moving things with my bodily force when the truck is on the ground. Any suggestions? I will raise the rear end tonight and turn the wheels by hand to see if I hear anything. It is really hard to hear with the engine running; sometimes I think I'm hearing things. This morning I shut down the engine and listened while the truck was coasting. This always happanes at very low speed, like when coming to a stop, without engaging the brake pedal. Any help?

 

Did you check the front axial joints ? also the u-joints can feel tight /good and the drive shafts may need to be remove to see if they pivot freely, if all that checks out then removing the diff. cover and making sure that its ok in there, no excesive stuff floating around.

 

When I did the rolling to a stop test this morning, I could definitly feel a grind of something. It wasn' t constant though. It happened at low speed. I'll see if I can repeat it tonight. I did change the diff lube back in Feburary. I had a problem then with the LSD additive. I used some stuff from the local parts store, not the dealer. It was Sta-Lube equa torque. It took 12 oz for there to be no clutch feel or groan, if I remember correctly. I used Redline Lightweight Shockproof oil. I hope there wasn't a compatability problem with this combination. When I first noticed this problem, I added another 2 oz of additive. That didn't help at all. I don't think it is the clutches because it happens when going straight. I also cannot duplicate 100% of the time. I'm prepared for the worst.

 

sounds like yoak bolt is loose on rear end does rear of drive shaft seem loose

 

Since checking the obvious did not reveal the problem, you should jack up the rear end and put it on safety stands. Remove the driveshaft and rotate the pinion slowly to feel for the problem. Check for oil leaks and movement, and rotational feel, should be smooth. Next check the u joints for freedom of movement, should not be tight. Then check the carier bearing if it is a two piece driveshaft.If you can not locate it yet, turn the trans output to feel for looseness and noise, then go to the front axle, make sure the front axle releases and freewheels and check the wheel bearings. Also check the rear wheel bearings, and all the lug nuts.

 

I caved and called the dealer. I'm bringing it in tomorrow for inspection. I'm just not all that good at diagnostics, and I don't want to follow any false trails. We'll see what the techs say. Since I can't always repeat the problem, maybe I'm just paranoid. I should know something tomorrow afternoon.

Thanks for the suggestions. I will keep everything in mind when I talk to the service "salesman"