Metalic clanking sound coming from drive shaft/rear end

[Napoleon_Tanerite]

This just started two days ago after returning from an uneventful 1200 mile round trip down to FL. On acceleration and often when changing gears from P to D or D to R I hear a fairly loud CLANG sound coming from the rear end. It sounds very much like something hitting the drive shaft or exhaust pipe-- a hollow metallic clanking sound. On acceleration the sound persists in increasing frequency up to 10-15mph. The sound is not present on deceleration.

I cleaned the undercarriage (lots of mud) and inspected everything. Nothing appears out of place. I shook and kicked both exhaust pipes and the drive shaft and they didn't budge, and I couldn't replicate the sound.

The rear differential had the fluid changed about 1500 miles ago. The fluid change was uneventful, and the gears looked new.

So what could this sound be, aside from annoying and expensive sounding?

 

[1986Blazerk5]

Check the U-Joints, its possible that with the mud and the 1200 mile trip that they went bad

 

[hoop]

U-Joints

 

[Napoleon_Tanerite]

LMC Truck Parts - Page 135 Is the U joint set listed on that the correct replacement? Seems too cheap, what's the catch?

 

[FMJ]

you can get the u-joints at any auto parts store


http://www.autozone.com/autozone/pa...42?counter=0&itemIdentifier=64133_0_1904_2935

 

[Napoleon_Tanerite]

yep, i just went out to the truck and rolled it back and forth. The joint between the drive shaft and the rear diff has a fair bit of play in it. Looks like I've got a project tomorrow.

 

[Napoleon_Tanerite]

You guys were spot on, the rear u joint was shot. One of the spokes on the differential side was completely trashed.... Forget pin bearings, there was nothing in there but black dust. On the plus side the rest of them were good, but I went ahead and changed both ends anyway. Those things were WELDED in there with mud too!