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Username Post: Rear end clunk        (Topic#182549)
Thurman55 
"7th Year" Silver Supporting Member
Posts: 747

Loc: Albany,Ga. Gold Member
Reg: 05-23-02
02-18-08 01:57 PM - Post#1369071    

2007 GMC Sierra, CC, NBS, with posi--at approximately 15,000 miles it started having a clunk sound in the rear end. Sometimes after I stop, sometimes after I have moved forward a few feet. Actually feels like someone bumped into me when sitting still. The local dealer (joke) says it is inherent with the new posi units, something to do with the clutches slipping. Truck still drives fine, and pulls my work trailer fine. Trailer loaded is well below the max weight. Any others with this noise?

 
LMC Trucks
Bad Bowtie 
Valued Contributor
Posts: 4585
Bad Bowtie
Age: 42
Loc: TX
Reg: 07-04-03
02-18-08 02:07 PM - Post#1369078    
    In response to Thurman55

Sounds kind of like the driveshaft slip yoke is dry...?
GMC. We are Professional Grade.

http://www.cardomain.com/id/2004VHO


 
Thurman55 
"7th Year" Silver Supporting Member
Posts: 747

Loc: Albany,Ga. Gold Member
Reg: 05-23-02
02-19-08 05:19 PM - Post#1370144    
    In response to Bad Bowtie

Thanks, I'll run that one by the service manager at the local dealer and see if he knows what a driveshaft yoke is. I do, and I'll check it.

 
tri5ss 
"7th Year" Silver Supporting Member
Posts: 2572
tri5ss
Age: 63
Loc: Massachusetts
Reg: 12-14-00
02-20-08 06:29 AM - Post#1370483    
    In response to Thurman55

My neighbor's Tahoe was doing the same thing. The dealer also told him it was inherrent with the truck. My neighbor said BS and kept pushing the issue. They finally found that the liners in the rear springs had fallen out and the clunking noise was from the springs moving around. Especially on takeoff where they are working to control axle wrap. I'd have my dealer check that also and accept nothing but the elimination of your noise.

Randy
Tri5SS
'55 210, GMPP ZZZ, 200 4R, 12 bolt 3.73 posi, CPP P/S, ABS D/B.

http://www.picturetrail.com/tri5ss

Nothing is foolproof to a sufficently talented fool!


 
91SilverZ71 
Forum Newbie
Posts: 88

Loc: Ohio
Reg: 04-27-05
02-20-08 09:40 AM - Post#1370585    
    In response to tri5ss

I don't know if this is the problem but GM calls for a special grease on the driveshaft splines. It's GM Part No. 12345879.

Summit Racing
GM Performance 12345879 $39.99
Estimated Ship Date: 3/7/08
Brand: GM Performance
Part Number: NAL-12345879

CHASSIS LUBE

http://store.summitracing.com/partdetail.asp?autof...
Sam

1991 Silver Chevrolet K1500 4WD * Regular Cab *
Long Bed * Z71 * 5.7L V8 * 4-Speed Automatic *
3.73 Axle Ratio with Locking Rear Differential


 
Tinman05 
Forum Newbie
Posts: 41

Reg: 11-13-07
02-20-08 07:19 PM - Post#1371003    
    In response to 91SilverZ71

I know stuff like that makes me want to pull my hair out sometimes... I used to work for a dealer and we had a truck with a posi trac come in with the same problem but it would also pop going around turns. Turned out to be the wrong lube in the rear end. We spent a week trying to figure it out. Finally after going through ALL of the dealer steps to diagnose the problem (bunch of BS) if you ask me. We added the recommended fluid and Additive and it went away after about 5 miles.
92 Mustang LX 5.0 Convertible
03 Durango 4x4 SXT - SOLD
07 NBS Silverado Crew Cab 1500
99 Yamaha 1600 Roadstar


 
elcamino 
Valued Contributor
Posts: 4997
elcamino
Loc: Lake Superior-Michigan US...
Reg: 03-30-00
02-21-08 09:42 AM - Post#1371352    
    In response to Tinman05

You are not supposed to put any additive in a G80 Locker!

The use of any additive in locking rear axles (G80) is not recommended. Rear axle additives are designed for use in limited slip differentials which are normally installed in cars. All light duty trucks equipped with RPO G80 make use of a locking differential and the use of additives will delay the engagement of the locking mechanism and may decrease axle life.

This is right from GM service information..
Mike
2009 Cadillac CTS4 AWD Performance Sedan
2012 GMC Sierra AWD Denali 6.2L


 
Bad Bowtie 
Valued Contributor
Posts: 4585
Bad Bowtie
Age: 42
Loc: TX
Reg: 07-04-03
02-21-08 12:41 PM - Post#1371469    
    In response to elcamino

I'm with u "Tinman05".
GMC. We are Professional Grade.

http://www.cardomain.com/id/2004VHO


 
Mikey1946 
Senior Member
Posts: 528
Mikey1946
Loc: Minnesota
Reg: 04-02-02
02-21-08 03:58 PM - Post#1371598    
    In response to Thurman55

Just search the OBS Silverado forum (99-06 Fullsize Trucks, Vans, Suburbans, Tahoes, Avalanche) and you discover how pervasive a problem driveline clunk is

One would hope that GM fixed old problems with the new design but I'm guessing not. I wonder if the clunking steering wheel problems been resolved with the NBS??

Drive line design, along with a build up of manufacturing tolerances, provide for driveline slop/slip. It's more noticeable in some vehicles than others. It's generally been treated by slopping grease in the slip yoke.

I sure Chevrolet Dealer Service will have a "that's normal" bulletin for you if you ask.

"The machinations of my mind are an enigma."

Patrick Starfish


 
97_cHeVy 
Senior Member
Posts: 252
97_cHeVy
Loc: Texas Hill Country
Reg: 01-02-03
02-21-08 06:14 PM - Post#1371712    
    In response to Mikey1946

My dad's '97, friend's '97, '99, '01, and my '03 all have developed that same damn clunk in the rear end. Grease up the slip yolk or enjoy that "tap on the rear bumper" feeling you get everytime you stop or take off from a stop light. Nature of the beast i guess.

Ben
1999 GMC Z71 Classic

Ben


 
CaptainK 
Senior Member
Posts: 8242
CaptainK
Loc: Maryland
Reg: 02-25-02
02-22-08 05:48 AM - Post#1371981    
    In response to 97_cHeVy

  • 97_cHeVy Said:
My dad's '97, friend's '97, '99, '01, and my '03 all have developed that same damn clunk in the rear end. Grease up the slip yolk or enjoy that "tap on the rear bumper" feeling you get everytime you stop or take off from a stop light. Nature of the beast i guess.

Ben



Or, install the new nickel plated slip yolk and have the problem go away for good
'99 Silverado (NBS)


 
Mikey1946 
Senior Member
Posts: 528
Mikey1946
Loc: Minnesota
Reg: 04-02-02
02-22-08 04:17 PM - Post#1372378    
    In response to CaptainK

How does nickel plating the slip yoke fix the problem
"The machinations of my mind are an enigma."

Patrick Starfish


 
Trevor350 
Senior Member
Posts: 744
Trevor350
Age: 26
Loc: Georgetown/College Statio...
Reg: 01-25-06
02-22-08 09:17 PM - Post#1372564    
    In response to Mikey1946

is the slip yoke that piece coming out of the tranny connected to the driveshaft?
2007 Summit White SCSB Silverado
3" BL
2.5" CCM
305-70-17 Terra Grapplers
Magnaflow


 
CaptainK 
Senior Member
Posts: 8242
CaptainK
Loc: Maryland
Reg: 02-25-02
02-25-08 04:29 AM - Post#1374035    
    In response to Mikey1946

  • Mikey1946 Said:
How does nickel plating the slip yoke fix the problem



For the life of me I cannot recall the details on it (I'll see if I can dig them up though) but I do know that it works (had it replaced on my 99 that had the infamous driveline "thump" on stops and starts)
'99 Silverado (NBS)


 
elcamino 
Valued Contributor
Posts: 4997
elcamino
Loc: Lake Superior-Michigan US...
Reg: 03-30-00
02-25-08 09:59 AM - Post#1374243    
    In response to CaptainK

Non-corrosive, does not rust.

If you grease the oem one all the time so it never rusts, then it won't bind.

Mike
2009 Cadillac CTS4 AWD Performance Sedan
2012 GMC Sierra AWD Denali 6.2L


 
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