Weird driveline noise when accelerating

[GuyZ71]

Here's the deal. Whenever I accelerate from a dead stop I get a weird sound from the driveline and I can't exactly tell where it's coming from. It feels as if a clutch either in the auto tranny or the rear end slips for a split second before grabbing and when it does there's a mechanical "clunk" sound. It only does it on moderate acceleration from a dead stop. If you're rolling at all it doesn't do it. I don't have any other abnormal noises while up-shifting or down-shifting but I do have a "clunk" when shifting from Park to Reverse. I bought this truck from my father and he said it's done this from day one and he took it to the dealer twice and both times they told him it was normal but couldn't offer any explanation for it. The part I don't understand is while trying to figure this problem out I'll power-brake the truck slightly just to put a load on the driveline and when I let off the brake and start to pull away the clunk is there. There's also a noticeable seat-of-the-pants feeling as if there's slop in the rear end or tranny because it feels all the world like a clutch slipping a hair before it grabs. If I floor it from a dead stop the sound is not there and there's no feeling of slipping. This truck has never towed anything over 400lbs. and my father babied it so I know it's not an issue of abuse.

 

Any thoughts

[Cool Zr2]

u joints, they are bad.

[GuyZ71]

That's my thought on the noise when shifting out of Park and into Reverse but I would've thought that when power-braking a little there would be enough load on the U-joints to stop any noise from slop. What the hell, I might as well replace them and see what happens.

 

Thanks for the reply!

[bob002500]

could it be the g-80 locker ingaging?

[az'03Silverado]

I don't think it's the u-joints. My '03 has done the same thing since I bought it brand new. With the Ext-cabs, the driveline is very long and has several joints along the way from the tranny to the diff. The 'clunk' is nothing more than a combination of the brakes releasing, the tranny engaging, and the small amount of slack in the drivetrain, due to its length, being taken up. It's more apparent after a relatively firm stop. I've heard, also, that on firm stops, there is a slight negative axle wrap that occurs and the brakes hold the rear axle/springs in that position until you let the brakes go. That can also contribute to the noise/feeling. I wouldn't worry about it.

[Shaners]

I'd look at the slip yoke and the Universals...

[NOS#9BIGMAC]

my truck does the same thing started doing it after it started the "clunk" when I put it in gear. It's starting to do it around corners now when I lay on it I already know it'sthe U joints but I want to find an extreme duty set so I'm gonna shop around for a bit

[jhm]

Drive line lash. Some have more than others, you could start replacing u joints etc but it could make it worse.

[NOS#9BIGMAC]

I didn't think about that but either way I can't ignore it until my driveshaft drops Witch happend to my girlfriend only her truck ended up in a fireball after the driveshaft went through the gas tank Shed kick my arse if I tried to ignore it. hope she doesnt read this thread or I may be in trouble

[GuyZ71]

I was told there was a TSB about this problem. The solution was a nickel plated yoke. Anyone know what specific TSB number this was and how much it costs?

[Wingnut]

Check this thread.

 

Reading through it, it seems that it might be exactly your problem. Hopefully, it helps.

[frdfandc]

It's starting to do it around corners now when I lay on it

Your clunk around corners when you lay on it is probably the rear diff. Normal.

[budhayes3]

I had the nickel plated yoke installed, transfer case flushed, and a few other trips to the dealer all while under warranty for the infamous driveline clunk. Five years later, clunk is still there. It's annoying, but doesn't seem to harm anything. Still, it's always best to get it checked out just to be sure and for piece of mind.

[DJinCO]

Turn up the radio.

[budhayes3]

Turn up the radio.

Or get a louder exhaust