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Transmission or Driveline 'Clunk'...


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rjdjbd's Avatar
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February 2nd, 2007, 5:42 PM   #1  
Transmission or Driveline 'Clunk'...

Hello everyone;

New member here, with a question regarding my 2003 Suburban LS, 1/2 ton 4-wheel drive. Since new, ittypically makes a 'clunk' sound when upshifting from second gear to third. The local dealer originally said that there was a problem and attempted a couple of repairs, including replacing a 'slip yoke'. Not sure where that is, or if it has anything to do with the transmisson, which at one point is where Chevrolet states the noise is coming from. (To me, it sounds like it comes from the rear of the vehicle.) Chevrolet has stated that there is a Technical Bulletin regarding this issue and that it is now considered 'normal' but do not have the bulletin. What causes this clunk and why won't Chevrolet deal with this issue?

Thanks for any imput regarding my question...

 
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February 2nd, 2007, 8:30 PM   #2  
RE: Transmission or Driveline 'Clunk'...

This is probably the bulletin:

Document ID# 1430424
2003 Chevrolet Chevy Suburban - 4WD
--------------------------------------------------------------------------------
Information on 2-3 Upshift or 3-2 Downshift Clunk Noise #01-07-30-042B - (Jan 16, 2004)
Information on 2-3 Upshift or 3-2 Downshift Clunk Noise
2004 and Prior Light Duty Trucks
2003-2004 HUMMER H2
with 4L60E or 4L65E Automatic Transmission (RPOs M30, M32)

This bulletin is being revised to add the 2004 model year. Please discard Corporate Bulletin Number 01-07-30-042A (Section 07 - Transmission/Transaxle).

Some vehicles may exhibit a clunk noise that can be heard on a 2-3 upshift or a 3-2 downshift.
During a 2-3 upshift, the 2-4 band is released and the 3-4 clutch is applied. The timing of this shift can cause a momentary torque reversal of the output shaft that results in a clunk noise. This same torque reversal can also occur on a 3-2 downshift when the 3-4 clutch is released and the 2-4 band applied. This condition may be worse on a 4-wheel drive vehicle due to the additional tolerances in the transfer case.
This is a normal condition. No repairs should be attempted.
--------------------------------------------------------------------------------

Hope this helps

 
rjdjbd's Avatar
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February 3rd, 2007, 4:40 PM   #3  
RE: Transmission or Driveline 'Clunk'...

RonH;

Thanks for the reply; is this consistent with Chevrolet having replaced the slip yoke? Seems like the bulletin addresses the transmission, but maybe they were trying to eleminate some driveline slack...

 
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February 3rd, 2007, 7:37 PM   #4  
RE: Transmission or Driveline 'Clunk'...

Sorry, don't know the answer to that.

 
engine2's Avatar
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February 13th, 2007, 8:34 PM   #5  
RE: Transmission or Driveline 'Clunk'...

Did you have the tranny mounts checked as well?

 
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November 12th, 2007, 10:36 PM   #6  
RE: Transmission or Driveline 'Clunk'...

rjdgbd's description of drivetrain clunk sounds exactly like what my 2002 4WD 1/2 ton Suburban had from day 1. The dealer also told me this was normal, but didn't cite any tech bulletin. About two months ago, at 47,000 miles, the pinion and carrier bearings went out in my differential to the tune of $1000+. The Tech Bulletin RonH cited refers to 2003 and 2004, so perhaps this doesn't apply to my vehicle. Any thoughts on why my rear-end would go out at so few miles? I tow a 17' powerboat a half-dozen times a year, but surely a Suburban can handle that. (BTW, a torque-reversal just doesn't sound like a good thing.)

 
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November 14th, 2007, 2:38 PM   #7  
RE: Transmission or Driveline 'Clunk'...

The TSB above applies to your 2002 as well, it is applicable to all GMT800 trucks and SUV's equipped with the 4L60E/4L65E transmissions built prior to 2004.

A "torque reversal" happens everytime you transition from having pressure on the gas pedal to releasing it (and vice versa) while you are driving.



 
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November 14th, 2007, 4:58 PM   #8  
RE: Transmission or Driveline 'Clunk'...

Thanks for the info. Do you think there's any "smoking gun" here with regard to the bearings in my differential going bad at just 47K? I pulled out my service paperwork from '03 which documents my concern then about the clunk I was feeling way back then. Convinced it was normal, I just let it go. I think it's worse now and am worried about damaging the new bearings.

 
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November 14th, 2007, 5:38 PM   #9  
RE: Transmission or Driveline 'Clunk'...

You should speak with the service manager at the dealer; run your concerns by him and simply ask if he could get with GM and see about a goodwill (no charge) repair, in your case a refund.


The damage to your rear-end was most likely the result of a manufacturing deficit; either by way of a faulty component or improper assembly.

 
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November 19th, 2007, 9:31 PM   #10  
RE: Transmission or Driveline 'Clunk'...

Driveline clunk IS normal on newer Chevy's. If it isn't I'm the most unlucky person in the world. '96 Blazer, '96 Sierra, '99 Z71, and now '02 2500 'burban. All of them exhibited this. My friend has an '02 Silverado with the same issue. When you think about the tolerance stack up on the many, many components required to transmit power to the rear wheels it's amazing more manufacturers don't have this problem.

That said, normal is not acceptable. This one issue gives Chevy (GM) a huge blackeye in the "fit and finish" department. It just sounds cheap. I hate it.

BTW, I have had tohave the tranny replaced in every one of those vehicles except the Z71. My cousin is driving itwith no problems even today (130K+ miles, unheard for chevy 7004R). The rear end did come apart on me though while towing 6K lbs.The truck had aftermarketaxles and a locker though and the guy before me (first 60K miles) drove it strictly on the street. It also had .410 gears and massively oversized tires. These things explain away the rear end coming loose at 110K miles, at least in my mind.

If you have doubts about the driveline clunk, go to a used lot and tell them you're looking to tradeyours in and want to test drive some. Simple test, before you leave the parking lot, put the truck in reverse andback up about 5-10 feet. Then put the truck in drive and listen. I'd almostbet my tractor you'll hearthe thud. That's the sound of the driveline "wrapping back up",taking all the slop out of the gears, chain drives, splines,yokes, and worn bearings in the driveline.

I'm betting you're carrier bearings were installed incorrectly at the factory or some other component (ringgear or pinion more likely). I'm also guessing if you had a catastrophic failure you have new ring and pinion already and they should have been installed correctly this time. If you didn't have those replaced when the bearings failedthe problem may still exist if that's where it originally was. It would likely be evident though, if you hear a loud whirring when you left off the gas that disappears when you accelerate again you may have alignment issues between the ring and pinion gears.

Otherwise, you've got yourself a genuine Chevy. Enjoy the clunk!


 
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