QDear Tom and Ray:

My son owns a 2003 Silverado 1500 four-wheel-drive Regular Cab Chevy truck. We hear and feel a loud clunk from the rear of the vehicle when starting from a stop. If you concentrate and go very slowly, nothing will happen, but if you take off from a stop normally, you feel as if someone has hit you from behind. The Chevy dealership has lubed the splines and given us a bulletin from GM stating that this is "Driveline Lash" and is normal in all newer trucks. We are wondering if you have heard of driveline lash, and is it "standard" in all GM and other makes of trucks? We will never be able to sell this truck if the prospective buyers feel a clunk. My husband says that it probably needs a new rear end and that the dealer does not want to go through the expense. The truck currently has 33,756 miles. -- Diane

ARAY: Unfortunately, driveline lash has been something of a trademark of GM trucks for the past half-century or so. It results from excessive slop in the differential, between the ring and pinion gears.

TOM: You usually hear it go "clank" when you change directions -- going from drive to reverse, or vice versa. The noise comes from those gears slamming against each other when the drive shaft changes direction. The sound is then transmitted to the front of the truck through the hollow tube of the drive shaft.

RAY: But what you've got doesn't sound like textbook driveline lash, Diane. Normally, you hear it once when you drop the transmission into gear; you don't normally get it again when you start up from a traffic light. So either you've got a particularly bad case of driveline lash (in which case it will get worse and start howling), or it's something else.

TOM: And the most likely "something else" is a transmission problem.

RAY: Here's what I'd do: Tell the dealer you're interested in his driveline lash theory, but you'd like to drive another, similar truck to compare the two. I'm sure he's got another '03 on his lot somewhere that you can drive. If it sounds the same, you might be out of luck. In which case, I'd just be sure to save the repair order in which you complained about the symptoms and they dismissed it as driveline lash. That way, should it get worse or should the transmission fail completely, you have a record of having brought it to their attention while the truck was under warranty.

TOM: But if the other '03 Silverado you drive does not exhibit the same symptoms, then you have a legitimate case to make that they need to fix your driveline lash. Try giving the dealer a tongue lash.

RAY: Actually, your best bet is to be persistent but polite. Your dealer will be more likely to want to help if you approach this as a problem you two need to solve together, rather than arriving with baseball bats and a couple of World Wrestling Entertainment impersonators.

TOM: Right. Save that approach for later.

RAY: If, in the end, the dealer won't help you, ask for an appointment with the Chevy zone manager. A zone manager has more authority, and might be more sensitive to seeing your follow-up complaint in the newspaper a few months from now.

Dear Tom and Ray:

Recently, I had my tires rotated. After driving about 100 miles, I started noticing a bumpy noise. It felt like a flat tire, but I kept checking and the tires looked fine. After another 40 miles, it was getting a lot worse. The tires still looked good, but I checked the lug nuts this time. All the lug nuts were so loose on the driver's-side front wheel that they almost fell off in my hand. Did driving on this wheel like that cause any other damage to the car? Folks at my office said it could have, but the guy who forgot to tighten my lug nuts said it was okay. Thank you. -- Judy

TOM: Jeez! We're glad you caught it when you did, Judy. As someone who has seen his rear wheel pass him on the highway, I can tell you it's not a fun experience.

Aside from the fact that your life was in danger, you've probably done no other damage to the car. Once in a great while, you'll see a loose wheel actually cut into the wheel studs (the things that the wheel nuts screw onto). But those wheel studs are tough, and most likely, no damage was done.

RAY: But to make yourself (and us) feel better, get a second opinion. On our Web site (www.cartalk.com), you'll find a service called the "Mechan-X-Files," which is a database of mechanics personally recommended by our readers and listeners. Enter your Zip code, find one who sounds good to you, and have him double-check your wheel studs for damage. And if you like the guy, make him your new mechanic, because you need one.

Got a question about cars? Write to Click & Clack in care of The Post, or e-mail them by visiting the Car Talk Web site at www.cartalk.com.

(c)(c) 2005 by Tom and Ray Magliozzi

and Doug Berman