The GMC Owners Group

alumitim said:

I recently purchased a 2006 Sierra 1500 SLE2. On the original sales sticker it shows an H.D. rear locking Differential. Today was the first day I have driven it on the ice and I noticed when taking off it started to spin and made a couple of clunking noises from the rear diff. Once I am driving it sounds fine and I understand that it may just be the locking differential, but was hoping that someone that has the same differential could clear it up for me.
Also if you know anything else about the diff that would help as well.
Tim

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Its normal, the axles are locking together to get more traction and unlocking to go around corners or on slippery conditions. I think this is one of the really cool things about chevy trucks. You won't get a limited slip axle on a lot of F or D trucks. This is the reason your truck moves and while driving in rain or ice and the guy next to you is setting still. I think your owners manual tells you all about this. Trust me on this, Sierra's, Suburban (limited slip), SWB V8 5 SPD (limited slip), SWB V6 5SPD (open Diff). Both limited slip trucks made the clunk sound your talking about. The open diff truck does not.

Other drive-line noise causes.

Anytime you have a gears or a slip yoke you have to have a small amount of clearance. This includes: axle splines, spider gears, ring and pinion gears U joints (2 or 3 in your truck) a slip yoke, all of the gears in the transmission, the torque converter or clutch. This clearence adds up. The more gears or yokes in the drive line the more lash. On excelleration you should not be able to feel this lash unless you have a manual trans and don't shift smoothly. The only way to totally remove this lash would be to bolt the wheel directly to the crankshaft, impossible. I my self add some Marine Grease to the slip yoke spline to get ride of the clunk noise when i put it in to gear. (Don't share, my secret )

The longer the driveshaft and more torque the more "driveline wind-up". The drive shaft stores energy like a spring. All drive shafts do this.

You can feel the effects of both of these by holding transmission in a low gear, lightly excellerating and quickly taking your foot off of the gas pedal. The springy forward and backwards jerking motion is driveline wind up. The clanking sound is lash. People Have been complaining about this since somebody in the late 80's decided that a unloaded pick-up ,somehow, should ride like a Caddy.

Note also: the yoke on the driveshaft. 2004/2005 models, seem to have a problem with the splines being dry and the load causes the splines to lock and then suddenly release, creating a thump noise. you can solved the problem by putting high temperature never seize on the splines, or Marine Grease. Other recommend putting tranny oil on the splines regularily or a replacement yoke to replace the stock yoke. Good luck and hope this helps you and others with similar issues.