Neil, 2 wheel drive, or 4x4?

And how many gears in transmission, 6 speed, or 8 speed?

 

Ray—

4WD, 8-speed transmission, 6.2 liter engine.

Neil

 

I would check the rear diff gear oil. these rear diff's have a break in of about 1200 miles.. did you tow or haul prior to the first 2,000 miles ? also did you operate the truck for a long run at hyway speeds with truck odo less than 500miles on it ? that can cause the problem !!!!!!!!.
I did my diff rear gear oil change @ 10K miles . also I did the transfer case fluid change. I had a clunk when I would stop at a stop light/ /stop sign the I would get the clunk...
If the gear oil looks off color dark/gray etc. then you must remove the cover and clean up the diff box and the magnet on the cover. .. as your truck gets above 75K miles the diff box will not have much steel dust on the magnet cover.. new causes more break in steel dust.. I do the diff oil changes 40K miles.also transfer case if it looks off color..

 

Hi Friends,

My 2017 Silverado with 11K miles on it (still under warranty) has a bothersome problem. When initially putting it in 'Drive' and slowly starting out on a slight downward grade, when the transmission shifts from 1st to 2nd, a loud 'clunk' sound comes from the rear end. The 'clunking' will occasionally happen at other times as well, but it always happens under the conditions I described. I told a service writer at the Chevy dealership where I bought the truck new about this issue. He said, "They all do it." At that point, I knew I was talking to an idiot. (This particular individual has been less than honest with me in the past.)

Since the 'clunking' problem seems to be getting worse, I want to be able to show some understanding when I return to the dealership. Is the issue in the rear U-joint, or could it be in the differential itself? As mentioned, this is a nearly new, low mileage truck bought new. Thanks!

Neil

Neil, if it was me I would return to the dealership and DEMAND that their most senior tech take a short ride with you so they can see for themselves your issue. As you are painfully aware, there are a lot of service writers that don't know jack.

 

Ray-

Thank you for your response. There is indeed a TSB on this problem. I will be contacting the dealer from which I purchased the truck, Sutherland Chevrolet in Nicholasville, Kentucky. It is a good dealership. I'm sure they will make it right. I do need to get a better-informed service writer though.

 

this is the TSB
The issues with the 8-speed GM transmission are two-fold. First, some customers report the transmission shuddering frequently. Secondly, the shifts are very harsh between first to second, and then second down to first, especially when accelerating and the transmission is upshifting or decelerating and the transmission is downshifting. These conditions are most commonly observed under light and medium throttle applications, and as often during full throttle applications.

However, a new fluid flush appears to fix the issues, with some customers beginning to report a dramatic change in shift quality after swapping out the old juice. If the flush doesn’t fix the issue, the next step may be to replace the torque converter, which could be glazed.

you say clunking .........., so the rear diff is the problem .. you may also have the dealership replace the tranny fluid NOW so that the torque converter will get damaged ... I do not recommend NEW GM trucks .. GM does not care ! needs an updated fluid to protect the torque converter.
DEXRON III DAMAGED OLD GM 4L60 TRANNY'S.. I DUMPED DEXRON III IN 1999...GM FOOT DRAGGED DEXRON III UNTIL 2006.. THAT IS WHY GM WENT BANKRUPT.
GOOD LUCK ..
having the high horsepower engine I am sure the diff got overheated and the gear oil got cooked on the first 1200 miles of your driving.

 

Hi Friends,

My 2017 Silverado with 11K miles on it (still under warranty) has a bothersome problem. When initially putting it in 'Drive' and slowly starting out on a slight downward grade, when the transmission shifts from 1st to 2nd, a loud 'clunk' sound comes from the rear end. The 'clunking' will occasionally happen at other times as well, but it always happens under the conditions I described. I told a service writer at the Chevy dealership where I bought the truck new about this issue. He said, "They all do it." At that point, I knew I was talking to an idiot. (This particular individual has been less than honest with me in the past.)

Since the 'clunking' problem seems to be getting worse, I want to be able to show some understanding when I return to the dealership. Is the issue in the rear U-joint, or could it be in the differential itself? As mentioned, this is a nearly new, low mileage truck bought new. Thanks!

Neil

Neil, Does Your Silverado Have the LOCKING DIFFERENTIAL, Which is RPO Code (G80).....

 

he has a full load GM truck .... sure has a locker diff ...........COST ..$65,000 ............!

 

I purchased my Avalanche with a mystery clunk that presented similar to what you describe. The seller spent a year replacing parts, trying to chase down clunk, convinced it was in the front end. The day after I purchased truck, I took it to driveline shop, as I was convinced it was in the driveline. The driveline shop said not in driveline and sent me to an alignment/suspension shop. In less than 5 minutes, they found my tranny mount was loose, tightened it up, and clunk is magically gone.

You may not get that lucky, but it is definitely easy enough to check your tranny mount.

Good luck!

 

I purchased my Avalanche with a mystery clunk that presented similar to what you describe. The seller spent a year replacing parts, trying to chase down clunk, convinced it was in the front end. The day after I purchased truck, I took it to driveline shop, as I was convinced it was in the driveline. The driveline shop said not in driveline and sent me to an alignment/suspension shop. In less than 5 minutes, they found my tranny mount was loose, tightened it up, and clunk is magically gone.

You may not get that lucky, but it is definitely easy enough to check your tranny mount.
Good luck!

what is your vehicles year miles etc...? this 10 yr old ?

 

I looked you up on your ride. 2002 vehicle 240K miles on it dah sure gonna have hardware and body break down.
your oil light comes on at 3-4K miles,,, reason is the PCM turns it on at the mile use.

THE VEHICLE DOES NO DO A OIL LAB TEST ! I change my synthetic oil @7-10K miles its a 2000 5.3L GM truck. original owner.. mobil 5-30wt syn .............no clunks no transmission or engine work .. just fluid replacing.
I do not recommend high mile oil ...also use high quality oil filters purolator pure one ..I cut the filters to inspect the media quality.. jiffy lube filters IMO will never use ..

 

I understand I have an older high miles vehicle. I only point out that sometimes a simple overlooked thing can be the issue and it only takes 1-2 minutes to eliminate tranny mount as source of clunk.

As for oil changes and lights, thanks for the explanation. I had no idea why the light came on, or how jiffy lube magically got it to turn off. Are you sure the motor does not contain laboratory testing?

 

how to remove the oil change lamp,,, turn key ignition on , put the gas pedal to the floor 3 times, then start engine.. that is how to reset the oil change mileage warning lamp...
NO lab test of the oil condition, it is just a mile indication on the oil use. check your oil every week on level ground when the truck sits for a couple of hours. this is an old vehicle so that is why you have to check out the fluid levels leaks etc...also check the drivetrain/tranny fluids for color ...
YOU MUST USE DEXRON VI NOT DEXRON III ..IN THE TRANSMISSION ....GM banned dex III in 2006 because GM went bankrupt on the 4L60 transmission failures do to this failed fluid.
if you do the checks and fluid maint might last to 325K miles if you drive it easy..

 

Neil, Does Your Silverado Have the LOCKING DIFFERENTIAL, Which is RPO Code (G80).....

99Heartbeat,

I am very late in getting back to you. I've been swamped at work. To answer your question: Yes! It has a locking differential Code G80. In my mind, that would explain the clunking. I never even thought to check the detail report; in fact, it never occurred to me that it had a positraction read end. Does the locking differential resolves the problem in your mind, or do you think I should still take it to the dealer?

Thanks so much for your help.

Neil

 

I've had a couple of G80s and haven't had any clunking because of the G80
There is a complaint of a clunk because of a lub problems in the slip yoke (the one at the transmission). Grease will fix it, GM have replaced it with a nickel yoke.
And, it could be a wore u-joint

 

Neil
you have a eaton locking rear diff .. not a posi traction diff. years ago we with the OLD GM trucks did have a clunking noise when stopped at a stop sign or stop light then when the vehicle started to move it would clunk.. ray said the drive shaft yoke in the transfer case needed a grease .. this is an old GM truck issue ..
I do not believe your 2017 truck with low miles on it has this old GM truck clunk.
I would have the dealership check the fluids for level and condition . I would change the rear diff gear oil..

I have a Toyota truck also ,,,and the toyota has drive shaft grease fittings and also grease fittings at the yokes .. 4WD ..I did the rear diff gear oil change @5K miles on my Toyota ... oil looked dark not a brown color.. I check the drive train fluids @ every oil change on all my vehicles GM/Toyota ....
GM does not have any drive shaft grease fittings . I had to replace my GM 2000 truck drive shaft U joints .. one of the bearings on the u joint seized up causing a weird vibration ..I did find it because I dropped the drive shaft and found the bad U joint that caused the vib problem ..

 

@j cat your right, I did a quick scan of posts and didn't see the year of the truck, now I see it is in the title; sorry Neil, j cat is right that problem was fixed by 2017.

Neil, if you have the 8 speed transmission, are you aware that there has been a lawsuit launched to address a number of complaints with that transmission?
One of the complaints is a clunk when slowing to stop and moving from a stop.

 

Just read up on this post. Thanks for posting and I picked up a lot in the replies.

I had two old big 2-door Blazers (5.7liter Silverado trims, a 93 and a 94) with the 4L60E tranny. Had to have one rebuilt, now I see it was a known problem for a long time.

My question is, do we know of a similar problem with the 6-speed transmissions in a 2014 Sierra? If the problem existed in the 90's and up until recently, I presume there is a known issue encompassing this time period and model as well? It does seem to shudder every now and then, and mildly clunk some. Or maybe I'm just real sensitive to it now I've been reading about it?

 

Hi Friends,

My 2017 Silverado with 11K miles on it (still under warranty) has a bothersome problem. When initially putting it in 'Drive' and slowly starting out on a slight downward grade, when the transmission shifts from 1st to 2nd, a loud 'clunk' sound comes from the rear end. The 'clunking' will occasionally happen at other times as well, but it always happens under the conditions I described. I told a service writer at the Chevy dealership where I bought the truck new about this issue. He said, "They all do it." At that point, I knew I was talking to an idiot. (This particular individual has been less than honest with me in the past.)

Since the 'clunking' problem seems to be getting worse, I want to be able to show some understanding when I return to the dealership. Is the issue in the rear U-joint, or could it be in the differential itself? As mentioned, this is a nearly new, low mileage truck bought new. Thanks!

Neil

I have a friend who had the same problem with his. He had a double cab. It would be smart to keep on the dealership because it could cause an accident.

 

Hi Friends,

My 2017 Silverado with 11K miles on it (still under warranty) has a bothersome problem. When initially putting it in 'Drive' and slowly starting out on a slight downward grade, when the transmission shifts from 1st to 2nd, a loud 'clunk' sound comes from the rear end. The 'clunking' will occasionally happen at other times as well, but it always happens under the conditions I described. I told a service writer at the Chevy dealership where I bought the truck new about this issue. He said, "They all do it." At that point, I knew I was talking to an idiot. (This particular individual has been less than honest with me in the past.)

Since the 'clunking' problem seems to be getting worse, I want to be able to show some understanding when I return to the dealership. Is the issue in the rear U-joint, or could it be in the differential itself? As mentioned, this is a nearly new, low mileage truck bought new. Thanks!

Neil

Its not the diff its the trans. Have the Trans ECM reprogramed at dealer. About 200.00 cost
newest software #24276638
It will shift like new.