OK, THIS IS MY FIRST D/A CC 2500HD, IT'S AN 02'.


PROBLEMS: IN 4X4 T/HAUL TRANNY OR SOMETHING HOWL'S VERY LOUD AT ABOUT 2000-2200 RPM'S. HAD FRONT DIFF. REPLACED, AND STILL HEAR THE PROBLEM. ALSO GET SERVICE 4WD LIGHT ON AT START UP FOR 3 SEC. AND GOES OUT.


NEXT: BOUGHT THE TRUCK W/12,000 MILES ON IT W/STRAIGHT PIPE NO MUFFLER, 1ST TANK GOT 17-18MPG. PUT STOCK MUFFLER ON AND NOW GET 12.5-14MPG EMPTY.


I AM RUNNING AMSOIL SYNTHETIC IN EVERYTHING BUT TRANS., TRUCK HAS BEEN TO SAME DEALER 4 TIMES FOR SAME PROBLEMS W/ NO RESOLVE. SO I CALL GM, THEY SAY TRY A DIFFERENT DEALER AND SEE WHAT YOU COME UP WITH. THAT'S WHERE I'M AT NOW.


ANY HELP OR ADVICE WOULD BE GREAT, THANK'S AGAIN!!

Well, looks to me like you need to take the muffler back off.

The service 4wd lights on mine stay on too. As for the sound... don't drive on dry pavement in 4wd!


I just got back from a 1400 mile trip in my DM pulling an 18ft stock trailer. Only thing I didn't like was waiting in line at the fuel pumps in San Antonio where fuel was $1.44 cash. $1.58 or higher at most other places.Edited by: dutch

Mine has a howl in 4wd too. I read a post here that there was some type of problem but I cant remember what it was.

There is a TSB on the "service 4wd light" coming on. Look in the TSB section of the website for details. Had mine fixed at about 200 miles...


- jeff

I am sure you verified all four tires are the same size. Later! Frank

seen some t-cases making noise.

Mine, an 01, howled in 4WD. I'm not sure what the rpm was, speed was anything over 60mph. Just like yours, my front diff was replaced. However, they also went into teh T-case and replaced all bearings and the pump. They told me it was due to incorrect torque on teh front diff pinion. That caused excessive wear in teh front diff and the resulting front diff sloppiness caused excessive wear in teh t-case. Now that it's all been fixed, I have a howling at just about any speed!!