Question: As a longtime reader, I try to save every one of your articles that could pertain to me. My 2004 Sierra extended-cab 4x4 has had a clunking noise on moderate acceleration that's driving me nuts. I even drained the rear end this winter expecting to find some debris in the oil (there wasn't any). Sometimes after I spray down the leaf springs with WD-40, it's better for a while. Have any new TSBs been released about this since January 2005 (#01-04-17-0004A)? Did I do the right thing by putting the additive into the synthetic oil in the locking rear? It's supposed to reduce chattering and such. Are there any similar problems with the new GMs?

Answer: There's nothing new other than an update on the previous technical service bulletin to #01-04-17-0004B. And it simply adds the Escalade to the list of affected vehicles. This bulletin is in reference to "a clunk, bump, or squawk noise when the vehicle comes to a stop or when accelerating from a complete stop." The correction is the installation of an updated nickel-plated slip yoke at the front of the driveshaft. Otherwise, GM considers a driveline clunk on acceleration or deceleration a normal characteristic of the 4x4 driveline. But if WD-40 applied to the leaf springs is actually making a difference, take a look at TSB #03-03-09-002C. This one deals with "rear leaf spring slap or clunk noise, most apparent when the vehicle is operated over irregular road surfaces." The suspension fix is the installation of plastic spacers, front and rear, on top of the lower leaf. The term "chattering" always brings a limited-slip differential to mind. If you're getting a chatter from the rear on slow, sharp turns, it could be damaged limited-slip clutch discs or need of service with the correct rear axle fluid. Make sure you use the right stuff. Check with a dealer: There's a big selection of grades depending on your specific drivetrain and rear axle application.


If you have a technical question regarding your pickup, SUV, or van, feel free to contact Alex, a master technician with the National Institute for Automotive Service Excellence. Send a letter to him in care of Truck Trend Garage, 831 S. Douglas Street, El Segundo, CA 90245, or e-mail us at trucktrend@sourceinterlink.com. Please include the VIN with your question. Due to the volume of questions received every month, we cannot guarantee that everyone's question will be personally answered or will appear in the magazine.

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