Hi all, just picked up a 2004 GMC 2500. 6.0, 4.10's, positrac, the usual. The truck has 68,000 miles on it. I've been working through the kinks and issues for the past few weeks, and the only thing left is a scraping sound I get in first gear. it sounds as if something metal is rubbing against the flex plate, you can hear it inside and out of the truck. It only occurs when I'm on the throttle, the amount doesn't matter. However, if I let off and coast, it goes away. Then, it will go away when the trans drops into 2nd. Other than this, the tranny is fine. Smooth, well timed shifts, tow/haul works fine, etc. The fluid is the right color and there's enough of it, and the temp gauge doesn't get higher than I would expect. (I know a guy with an identical setup and he gets the same readings). I've been meaning to pull the flex plate cover and take a look, but I'm not sure what to be looking for. Any help is greatly appreciated! I get a lot of strange looks in parking lots....

P.S. the trans code is MT1, I think it's the one with the straight cut gears. It also has the VYU plow prep package.

 

Would you describe this as a "chirping" sound or is it more of a "grind" type noise?

Allan

 

Definitely more of a grind...no high pitch squeaking or anything like that. The best i can describe it is it sounds like something being dragged across the flex plate. It has that "hollow" sound like you're grinding something metal on a metal plate that's supported by bolts...if that makes any sense. I will try to take some sort of video and put it on Youtube tonight.

 

Since it only does it in first gear, I'd guess it's torque related. Check the motor mounts and rear mount.

Look very closely for any signs of the transfer case/transmission "grounding out" or rubbing on the under body. Also, this could be a rusted U-joint setting up this noise.

Beat on all the heat shields and see if any of them 'rattle'. And, a loose muffler baffle will just drive ya nuts trying to find the noise.

If all else fails, I'd suspect a cracked flywheel.

Hope ya find it!

Allan

 

I know this post was from many years back, did you ever find out what the noise was? I have an 07 with the MT1 trans as well and it makes the noise you are describing