i have a 1997 1500 5.7 liter 4X4 and have had an issue with clunking in the driveshaft ever since i bought the truck. My transmission broke after about a year and i bought a new jasper and the issue remained, so i thought it shouldn't be the transmission. i think it is a bad connection with the rear diff. but am not sure. any help would be great. Thanks!

 

Is it at slow easy driving or all the time. And how does a bump or a dip in the diving surface affect the noise?

 

its usually at a slow speed and i don't drive crazy. the clunk happens between the 1-2 shift and a smaller clunk at 2-3. The clunks also increasingly get louder as it warms up. i do notice that the shift is a lot louder after coming off of a speed bump.

 

Anytime I have ever had a "clunk" in the driveshaft area I always changed the u-joints out and that usually took care of any clunking.

 

thats what i had heard, but the joints are very firm and don't have any play. could still be it though

 

You cant tell the condition of a u joint by shaking it. You have to remove the shaft and work them around and see how they feel. There has also been a problem with the slip yoke that goes in to the trans getting rusted up. Clean it up and grease the devil out of it. Let us know if this helps.

 

Do a forum search for "slip Yoke" as it is a very common problem... but also check the U-joints as they are the 2nd most likely....

 

what kind of grease would you suggest, i dont wanna get the wrong kind.

 

That is a very good question as there is a special lube that should be used, it has to be compatible with hydraulic fluid / transmission fluid.
the lube: GM PART # 12345879

Here is the thread that has more info....
https://chevroletforum.com/forum/tah...ication-34373/


A few places you can find the lube
GM Performance 12345879 - GM Performance High-Temperature Grease - Overview - SummitRacing.com

 

Thanks everyone i greased the slip yoke and the clunk is gone. everything shifts smoothly. I also repacked the bearings on the ujoints while i was at it. Im so glad to have it fixed