Buddies 08 with clunking sound?

[mattymac]

Have a friend with a brand new 08 mega 6. 7 auto that he says when coming to a stop gradually everything is fine, if he hits the brakes pretty firmly and stops at a harder rate of deceleration the transmission downshifts into what im assuming to be first and he can hear and feel an audible "clunk" from the drivetrain somewhere. Im thinking the negitive slack in the drivetrain with the sudden downshift from the 6 speed causes the slack to be reversed causing the clunk? havent riden in it yet but the guy knows a bit about trucks and all things mechanical so Ill take his word. Any one else experiencing this with your 6. 7's? TIA!



Other than this he says the truck is great in all other aspects! And this coming from a guy who had two other GM's, a 6. 0 gasser that was lemoned and a 04. 5 LLY that seemed to be a good truck.

 

[Simplysmn]

Haven't had anything like that what so ever on mine maybe something loose ?

 

[mattymac]

He just picked up the truck about a week and a half ago and noticed it the first time he hit the binders fairly hard? I havent had time to drive or look at it he just stopped by my shop to see if I had heard of it before so I figured id check here if it is a known problem.

 

[Texas Ted]

Mine will do the same thing when the exhaust brake is on and the trans is in tow haul mode. It is a pronounced clunk depending on how much brake is being applied. Only happens in tow haul. Seems to be normal with the downshift.

 

[Drdorian]

Mine does the same - I thought it was coming from the u-joints so I took a look at them. There is a bit of slop, not enough to make me worried but I'll keep my eye on them every 10k miles or so.

 

[KKelly]

07.5 6.7L - Problems

Mine will do the same thing when the exhaust brake is on and the trans is in tow haul mode. My truck does it on the 3rd to 2nd gear down shift. If the roads are wet the rear wheels momentarily lock and the back end kicks out. I have brought the truck back to the dealer 3 times. Magically they can never seem to duplicate this problem or any of the other problems I am having with this truck. I then told the Service Manger and the Tech to get in the truck with me and go for a ride. The Service manager stated he was to busy to go. I then went for a ride with the Tech and was able to create the problem they could not replicate. After I was able to get the transmission to induce the loud clunk ( Sounds like the transmission is going to drop out from between the frame rails ) and lock the rear wheels repeatedly the tech said "That's Not Good". Apparently DC is working on a re-flash for a problem that doesn't really exist.

The other really annoying problems with this truck are:

The neck snapping engagement of the Exhaust Brake when you lift off the throttle !

The surging of the exhaust brake on steep declines !

The fact that it will not start after it is warm. The starter engages but the engine will not fire. I actually had it towed into the dealer after it left me stranded. Upon arrival at the dealer it fired when they tried to start it.

My trucks latest trick it that it now dies on the fly - It just shuts off !

My wife and kids now refuse to drive with me in this truck.

I am extremely displeased with this trucks reliability and drive ability.

All of these instances are not showing any codes and the dealer cannot figure it out. The dealer looks at me like I'm crazy. I even left the truck with the dealer for a week so the service manger could drive it home. Once again they were not able to replicate any of my problems. Suggestions would be greatly appreciated.

 

[Jeepstang]

if your willing to drive the truck to the DC area I can point you to a good tech

he is one of the best in the area he has done all of my warranty work without any arguing or denials of problems