So I believe I have drive line slack going on, most noticeable at low speeds. Say, in a parking lot let off the the gas and get a noticeable clunk. Anyone else have this going on on the new trucks?, any fixes? I don't think the dealer is going to fix it.

 

On the older GMT 800's it's something I've noticed a few times.

Remove the driveshaft and grease the splines on the driveshaft that go into the transmission or transfer case. You don't need a ton but a good amount will do and then bolt it back together. It may be your issue or it may not be, but it's worth a shot and technically free if you already have some grease laying around.

 

Its a slip yoke problem man. what FFDP said is the solution, for a while..then the grease extrudes and you'll hear a clunk again.

I have the same...had in on my 2003, 2010, 2012, and now the 2014. Get rid of the slip yoke is the only fix...

I do believe they put a zurk fitting in there in these trucks though....you may not have to pull the yoke out to grease it and make the noise go away.

If you lift the truck it will get worse....I lowered my 2010 and 2012 and it got a lot better...less play. The drop shortened the distance between the rear diff and the tail shaft...basically if you shorten a leg of the triangle (ie the height of the rear diff) the hypotenuse gets shorter.

 

Yes i notice this allot. even at higher speeds as well, like when coasting then going back to throttle....CLUNK

 

i have the same problem it's annoying when in traffic .

 

Oh ****...your so right.

 

I'm sure that many here will argue or doubt what I am about to say.

I am not going to say that there is no physical slack in the drivetrain, there is in any vehicle.

That being said; you can eliminate the clunk on most of these trucks(and many cars from GM) by adjusting certain parameters in the tune. Typically in the Gen 5 engine equipped vehicles I do this in the Driver Demand tables.

 

I have been thinking about this to. If the transmission is controlled by the actuation of the the throttle body to not only shift but to also soften the shift in the tuning "to save ware". That maybe the GM programming is wrong and hesitates to long from when i let off the pedal to get back on the pedal. Thus causing the driveline to clunk trying to catch up. I tore through everything but dismantling the diff looking for any indicators of excessive play or ware.

 

I have been thinking about running a tvs 2300 with blackbears tuning, but want the clunk fixed first while I still have a warranty if needed.

 

All drivelines have some slack in them. The machining tolerances of every single part between the crankshaft and the tires, adds up to a certain number. You tend to feel it more in these newer trucks due to the way they coast down. To increase the overall fuel milage of the entire sold fleet of GM vehicles, they have tried to save every drop of fuel as possible in a coast situation. This brings about a very "neutral" condition and when you apply accelerator pedal you feel the clunk or slack getting taken up.

If you go to a new GM dealership and drive ten trucks (all brought up to similar temps) you will feel it in pretty much every one of them.

Now, if yours is more dramatic than those ten trucks, then have it looked at. There are always exceptions and can be bad parts, bad machining tolerances, etc...

My $ is on this being within the average though.