Clunk and jolt coming from the back of the truck

**jaridd** · 10-22-2009, 06:29 PM

This is my first truck (01 1500 z71 extended cab). Every time I brake to a complete stop there is a fairly loud, as in I can hear it over conversation volume music and the A/C on, squeak/clunk and a jolt. From a seat of the pants measurement is feels like something is moving about an inch. When I start from a stop the same thing happens only it is a slight jolt/ clunk and squeak backwards. I have put about 7000 miles on the truck since I got it and the problem sounds like it is getting worse.
My initial thought was the motor mounts, I keep forgetting to check (my truck is parked about a half mile from where I live) but I am pretty sure that the sound/movement is coming from the back.

As I said, its my first truck and while I know it can't be normal, I am not sure how bad it is.

Thanks

**pearlbluesilverado** · 10-22-2009, 06:50 PM

thats clunk noise is not normal its not the motor mounts cause if it was the engine probably wouldnt still be running due to the fact that the fan would end up in the radiator.

**Mean_Green_95** · 10-22-2009, 07:41 PM

have ur u-joints checked. Those sound like some normal symptoms.

**jsburb** · 10-22-2009, 08:00 PM

Ok this is going to sound crazy but trust me this is it...After spending a ton of money on trying to fix the exact same problem you have I finally fixed it with a .99 cent rubber ball and some nasty slip yoke grease from chevy. What is happening is your slip yoke is getting hung up as you brake and acclerate causing a "clunk" noise. All you have to do is pull your slip yoke out and put a small rubber ball in before you re install the slip yoke and grease it with that nasty stuff from chevy. This will cure your problem! I know it sounds stupid but do it and you will be happy and save a ton of money and head aches in the mean time. If you need the part number on the grease I will get it when I get home.

**Beer Belly** · 10-22-2009, 08:58 PM

I just gotta ask......how did you come up with that fix ????

.....not saying it won't work, but who would of thought of putting a rubber ball in the yoke. I have a similiar noise (I think), dealer said it's normal.

**jsburb** · 10-23-2009, 10:09 AM

Well I came across a guy that raced desert with his gmc truck in the stock class and in talking to him I was telling him I loved my suburban but I had this crazy clunk that I couldnt find and he laughed and told me well try this trick....Like I said since I spent in upwards of a 1000.00 on trying to fix it I thought what the hell??? And it fixed it so cheers to him!!! Yeah the dealer always tries to pass the buck if you really dig into it there is a TSB on the yoke itself they replace it with a titanium yoke but you cant beat it.

**jaridd** · 10-23-2009, 11:33 PM

Thanks, Ill have to get a rubber ball to try it.

Is the number for the grease in the manual? If so I can just look that up.

**tbplus10** · 10-24-2009, 10:28 AM

The rubber ball sounds like a decent method of getting rid of the clunking noise. Driveshaft clunk's have been an issue for almost every make truck ever built, some are just louder than others.
The ball is replacing the grease that should normally pack the upper ends of the shaft splines. Make sure you dont use to large of a ball so it doesnt place extra stress on the transmission output shaft, this could be fatal to the trans if done.
Another issue to look at is worn springs, sometimes excessively worn springs (like Burb's tend to easily get) allow torque when braking or starting as they allow a fore and aft rocking motion.

**jaridd** · 12-17-2009, 05:55 PM

I know this thread has not been active for a while but it took me this long to actually get to work on my truck. I did not use a rubber ball I just greased the splines with some very high pressure grease from NAPA.
Here is a good link that explains the process pretty well
http://www.truckmodcentral.com/forum...ead.php?t=2504
Some things to note:
1. It would have been easier with a second person helping.
2. If you have an aluminum drive shaft like mine, it is really light, so don't be afraid of it falling.
3. You will probably need a pry bar or something to get the shaft out of the joint once you unbolt it.
4. WASH the underside of the truck before you start. This will prevent dirt from getting into your slip yoke and will keep stuff out of your eyes.

Oh and I almost forgot - the clunk is completely gone. 15-30 min of work for a lot of satisfaction.

**TJbear** · 12-19-2009, 11:31 AM

Wish it had worked for me. Mine had no grease at all when I removed the shaft. I greased it up with marine grade grease and no change. Lame...

Perhaps it is something else.