2008 Chev Silverado with clunk in drivetrain

My 2008 Chevrolet 1/2 ton 4 wheel drive recently developed "clunk" when going from drive to reverse. Note - front wheels disengaged. The "clunk" to me meant play and I figured it was in the rear driveshaft universal joints. This past weekend I crawled underneath with the transmission in neutral and could not identify any slop in the front or rear driveshaft universal joints. While twisting on the driveshaft I noticed that there is quite a bit of play in the differential. The driveshaft might rotate an 1/2 to 3/4 inch. I have never had a differential problem in a pickup. Are these pickups prone to rear end problems? Is that amount of play/rotation of the driveshaft too much? Seems like I have developed a vibration or rumble at highway speeds. Let up on the gas pedal (coast) and the vibration/rumble goes away. The vibration resembles a very low tire. Can the rearend be rebuilt or do people just put one in from a auto parts yard. Any ideas appreciated. Thanks.

Had something like that. One friend ended up with a junk yard rear. His rear was so bad you could pull the rear wheel in and out almost an inch! My Explorer needed a transfer case cause it was way low on ATF fluid. Clunk and thump noises. Don't GMs glue the spiders in? Crazy way to put a truck together. If you jack up one rear wheel see if you get maybe an inch of turn. More than that and you might need some bucks to come out of the wallet.

I'm not there to see whats going on but I have encountered a few of these trucks with spider gear and cross pin wear. It would be obvious during inspection if you were inclined to remove the cover, cross pin and spider gears. If you feel the problem is in the rear axle, you will at least get a probably needed fluid change if everything checked out. If you do pull the cover then inspect for slack or things moving where they shouldn't before taking pin and gears out though.

Since you found play, I doubt this is your issue but these trucks are also known for a clunk sound coming from the slip yoke going into the trans/t-case, mainly after completing a stop but sometimes from rev to drive or other way. The fix was either lubing the splines, replacing the yoke and/or maybe output shaft.

Double check/replace the rear U joint.

NOT quite sure where you are encountering the 1/2" to 3/4" "play", but some play in the "rear end" is normal.

Don't know what the history of the vehicle is, but unless it was kid/BLEM-driven and/or the gear lube in the rear end is NASTY and very metallic looking the odds are in favor of it being a U joint issue over being a rear end failure issue.

But STUFF happens!

With your description it could be either in the differential or u-joints. Look for a light brown stain at the cap seals on the u-joints and don't assume front or rear only. Noise can telescope through driveshafts. I prefer to check them with the wheels off the ground. Have you checked the fluid level in the differential? U-joints can be noisy and not exhibit much play. Also, you may want to pull the pinion yoke forward gently rocking it then move it vertically to check for pinion bearing wear.

You don't say how many miles you have on it, but pinion bearings start to get sloppy around 100K. If oil is leaking out the pinion seal, it's time to have the rear end rebuilt.

If you decide the rear end is going out, don't bother replacing it with a junk yard axle; it's likely to be just as bad as the one you have. You should be able to get it rebuilt for between 500 and 1000, the higher number if the ring and pinion set have to be replaced. If the truck doesn't have a posi rear end, this is a good time to install one.

I would take a close look at the CV joints on the front axles, even though you have the noise in 2WD.

While it is possible you have rear end troubles, I, like the others, encourage you to look hard at the rear u-joint. My 2004 had a rumble, for quite a while, I thought was a tire. Finally, after I thought I had checked it thoroughly, I got the wife to shift it between forward and reverse while I observed, and I finally found the rear U-joint bad. It had a grease fitting on it!!!!!!! Which tells me it had already been replaced. I never thought to look for a zerk. It was kind of a nasty bugger to replace. I had to really squeeze it to get the snap rings seated.

Check your u-joints. Hal

You got some good info with that much slack at the pinion I would have to remove the diff rear cover for a look. Removal of the drive shaft and cover for inspection is not difficult but may require a good trained experienced eye to locate the issue.

I associate slip yoke issues with a bump once the truck starts to roll the yoke binds up and pops.

Your issue is a common issue I googled it lots of info I was going to recommend GM #12345879 Special Lubrication on the slip yoke but ran across this TSB.



http://www.gm-trucks.com/forums/topic/103667-gm-special-greaseuse-it-or-not/

I googled "GM #12345879 Special Lubrication". Its expensive for a one time use and its eliminated some of those issues BUT they always came back in time. The price shocked me but the can has done a many slip yoke for me. I would guess I have lubed 50 are more with one can. I can not recommend any one fix I would be looking at the differential worn carrier/spider gear set ups are not that uncommon on a GM... Even if it were a U-joint issue it would not be a guess you would know a bad joint once the shaft was out.

My '92 K1500 does the same thing and it has done it as long as I remember,now has 145K on it and still going.

Can you run a magnet in the oil check hole on the rear-end to check for metal debris?

What an interesting set of answers. Everything from soup to nuts.......
Now for my opinion.......after having rebuilt hundreds of rears over my time as a mechanic.
First, there are many points of wear that can add up to a lot of play in the rear. The most common is from spinning in slippery conditions. There are 4 gears in the carrier that is the actual differential. Two side gears and usually two pinions. The side gears seat into the carrier and are splined on the inside to engage the axle splines. Where they sir in the carrier, they can wear out that opening causing some play. The pinion gears are mounted on a shaft that is pinned into the carrier. When they spin on that shaft, they will wear into it over time. These parts are not well lubricated, and are not meant to spin very fast. They are designed to allow one wheel to turn faster than the other to allow for turning. When the vehicle gets stuck in a slippery mess like mud, snow, or ice, the driver tends to attempt to escape by racing the engine and spinning the wheels. That causes these parts to spin faster than they were designed or intended to spin. This causes the lubricant to be expelled to some extent, and accelerates wear. This is the primary cause of excessive play in rears in my experience.

Now, having said all of that, the other possible points of wear would be the ring and pinion, the pinion bearings, and the carrier bearings.

Ring and pinion: if your ring and pinion had that much play, it would be accompanied by howling/whining either under acceleration or deceleration. If this noise is not present, your ring and pinion are OK.

Pinion bearings: If your pinion bearings are worn, the yoke on the front of the rear will be loose and will also move from side to side or in and out. If your play is only rotational, your pinion bearings are probably fine. Also, bad pinion bearings are usually accompanied by an oil leak.

Carrier bearings: When these get worn, they make a grinding noise like a wheel bearing. They may also cause ring and pinion noise.

Rebuilding a rear is very simple. Making it QUIET is NOT. Pinion depth, backlash, and bearing preload must be correct or the rear will be noisy.

Also note that a one line answer to your question from somebody a thousand miles away from you that has not seen the problem will not likely be of much value.

I hope that this can be of some help to you.

My '94 K1500 has done the same thing, it still has less than 70,000 miles. My neighbor used to have a '90 K1500 that sounded the same, he traded it off with 215,000 miles. The clunk has a hollow echo to it. When I tap on the drive shaft tube it has the same ringing sound. I suspect that normal play in the gear train and in the drive shaft slider are just enough to set off the resonance.

That's a very common problem on that style of truck. It is the slip joint on the drive shaft. My 2009 silverado has done it since new. Apply the GM grease maybe once a year and it will stop it, at least until it's time for new grease.

Thousands of trucks have this issue and it causes no apparent damage, it's just annoying.

X2, . Do this first, and check the ujoints while the shaft is out.

Just to add , check the level and condition of the transfer case fluid while you are at it. It can get low and black, smelly. It only holds about 2 quarts.

jimg.allentown has given you some excellent advise.

The only thing I will add is checking u-joints while the shaft is installed is only going to identify a joint that is really bad, when a cup dries up or there is load on the assembly play can be hard to detect.
Take the truck for a ride parallel to the side of a building or some other fixed structure, bridge traffic barrier etc, these do an excellent job of magnifying sound back at you.
Roll down your windows then accelerate firmly from a stop and listen for a fairly rapid tink tink tink noise.
If you hear this sound it is a good indication that likely a cup has dried out and the shaft should be removed for closer inspection.

Sounds like the clincher throw out bearing.