Scary noises, Drivetrain clang.
#1
01-09-2007, 04:10 PM
Scary noises, Drivetrain clang.
98 blazer 4x4 4door. When shifting from Park to Reverse I get a bad clang sound from the drive train under the initial load. Then R to Drive I sometimes get it again. Also after a coast when going back into an acceleration. It also makes the sound if I really mash the pedal from a stop or slow speed but in that situation it's more of a rattle than a single clang sound. It will fadeaway with speed on a hard start. I had my wife shift from N to R to N several times in the driveway while I was trying to locate it. As far as I can tell it seems to be coming from the transfer case. Is this right? I've only tried to locate this while in 2wd. Has anyone else had this or know what it may be? I'm at a loss. I'd appreciate any help or ideas
#2
01-09-2007, 08:55 PM
RE: Scary noises, Drivetrain clang.
To me "clang" sounds like a u-joint. Hollow driveshaft makes a clanging sound.I hope you have a lot of confidence in your wife standing on the brake. First with truck running, your foot on the brake,don't give it any gas,alternate slowly between reverse and drive (pause a few seconds in gear each way). If you hear a clang or a clunk doing that - then have thewife do it and you lay underneath and watch the yokes on the front and back of the drive shaft while she does it. They should not "jump" relative to each other, the u-joints job is to keep the 90 degree alignmen between the yokes. Does the truck vibrate while you drive? If so it's a sign of imminent failure
#3
01-10-2007, 12:14 AM
RE: Scary noises, Drivetrain clang.
I agree, I've heard the clang from the driveshaft when in fact the problem was worn u-joint needle bearings.
#4
01-10-2007, 03:07 AM
RE: Scary noises, Drivetrain clang.
Thanks for the advice. I'll be trying it in the morning. I do get a vibration but it's not very extreme and only between 45 and about 55 mph. But still, it's a vibration. As for faith in the wife standing on the brake?.....not with my insurance ; ) Faith in the parking brake. I'll post again with some results.
#5
01-10-2007, 04:24 PM
RE: Scary noises, Drivetrain clang.
Here's some more information straight out of a TSB from GM:
A/T - Clunk When Shifting From PARK/DRIVE/REVERSE
Bulletin No.: 99-04-20-002D Date: June 08, 2006 INFORMATION Subject:
Information on Driveline Clunk Noise When Shifting Between PARK and DRIVE, PARK and REVERSE or DRIVE and REVERSE
Models:
2007 and Prior GM Passenger Cars and Light Duty Trucks
2007 and Prior HUMMER H2, H3
2005-2007 Saab 9-7X
Supercede: This bulletin is being revised to add models and model years. Please discard Corporate Bulletin Number 99-04-20-002C (Section 04 - Driveline/Axle).
Important: The condition described in this bulletin should not be confused with the following previous bulletins:
^ Info - Discontinue Flushing and Replacing Transfer Case Fluid Due to Bump/Clunk Concern (Corporate Bulletin Number 99-04-21-004A or newer).
^ Clunk, Bump or Squawk when Vehicle Comes to Complete Stop or Accelerating from Complete Stop or Accelerating from Complete Stop (Replace Rear Drive Shaft Nickel-Plated Slip Yoke) (Corporate Bulletin Number 01-04-17-004B or newer).
Some owners of vehicles equipped with automatic transmissions may comment that the vehicle exhibits a clunk noise when shifting between Park and Drive, Park and Reverse, or Drive and Reverse. Similarly, owners of vehicles equipped with automatic or manual transmissions may comment that the vehicle exhibits a clunk noise while driving when the accelerator is quickly depressed and then released.
Whenever there are two or more gears interacting with one another, there must be a certain amount of clearance between those gears in order for the gears to operate properly. This clearance or freeplay (also known as lash) can translate into a clunk noise whenever the gear is loaded and unloaded quickly, or whenever the direction of rotation is reversed. The more gears you have in a system, the more freeplay the total system will have.
The clunk noise that owners sometimes hear may be the result of a buildup of freeplay (lash) between the components in the driveline.
For example, the potential for a driveline clunk would be greater in a 4-wheel drive or all-wheel drive vehicle than a 2-wheel drive vehicle. This is because in addition to the freeplay from the rear axle gears, the universal joints, and the transmission (common to both vehicles), the 4-wheel drive transfer case gears (and their associated clearances) add additional freeplay to the driveline. In service, dealers are discouraged from attempting to repair driveline clunk conditions for the following reasons:
^ Comments of driveline clunk are almost never the result of one individual component with excessive lash, but rather the result of the added affect of freeplay (or lash) present in all of the driveline components.
^ Because all of the components in the driveline have a certain amount of lash by design, changing driveline components may not result in a satisfactory lash reduction.
While some owners may find the clunk noise objectionable, this will not adversely affect durability or performance.
Bulletin No.: 99-04-20-002D Date: June 08, 2006 INFORMATION Subject:
Information on Driveline Clunk Noise When Shifting Between PARK and DRIVE, PARK and REVERSE or DRIVE and REVERSE
Models:
2007 and Prior GM Passenger Cars and Light Duty Trucks
2007 and Prior HUMMER H2, H3
2005-2007 Saab 9-7X
Supercede: This bulletin is being revised to add models and model years. Please discard Corporate Bulletin Number 99-04-20-002C (Section 04 - Driveline/Axle).
Important: The condition described in this bulletin should not be confused with the following previous bulletins:
^ Info - Discontinue Flushing and Replacing Transfer Case Fluid Due to Bump/Clunk Concern (Corporate Bulletin Number 99-04-21-004A or newer).
^ Clunk, Bump or Squawk when Vehicle Comes to Complete Stop or Accelerating from Complete Stop or Accelerating from Complete Stop (Replace Rear Drive Shaft Nickel-Plated Slip Yoke) (Corporate Bulletin Number 01-04-17-004B or newer).
Some owners of vehicles equipped with automatic transmissions may comment that the vehicle exhibits a clunk noise when shifting between Park and Drive, Park and Reverse, or Drive and Reverse. Similarly, owners of vehicles equipped with automatic or manual transmissions may comment that the vehicle exhibits a clunk noise while driving when the accelerator is quickly depressed and then released.
Whenever there are two or more gears interacting with one another, there must be a certain amount of clearance between those gears in order for the gears to operate properly. This clearance or freeplay (also known as lash) can translate into a clunk noise whenever the gear is loaded and unloaded quickly, or whenever the direction of rotation is reversed. The more gears you have in a system, the more freeplay the total system will have.
The clunk noise that owners sometimes hear may be the result of a buildup of freeplay (lash) between the components in the driveline.
For example, the potential for a driveline clunk would be greater in a 4-wheel drive or all-wheel drive vehicle than a 2-wheel drive vehicle. This is because in addition to the freeplay from the rear axle gears, the universal joints, and the transmission (common to both vehicles), the 4-wheel drive transfer case gears (and their associated clearances) add additional freeplay to the driveline. In service, dealers are discouraged from attempting to repair driveline clunk conditions for the following reasons:
^ Comments of driveline clunk are almost never the result of one individual component with excessive lash, but rather the result of the added affect of freeplay (or lash) present in all of the driveline components.
^ Because all of the components in the driveline have a certain amount of lash by design, changing driveline components may not result in a satisfactory lash reduction.
While some owners may find the clunk noise objectionable, this will not adversely affect durability or performance.
#6
01-10-2007, 04:36 PM
RE: Scary noises, Drivetrain clang.
Thanks for the TSB. That sounds exactly like what I've got. Well, I got under there and tried it. And I'm alive. I saw some things but I'm not really sure What I was seeing. When running and shifting from D to R the driveshaft makes an initial jump, but I'm not sure how much is to be expected.. ?? Also on the front joint I get a difference in the gap between the tranny output and the driveshaft yokes. Going one way I can barely get a finger inside, going the other there is room for my finger and some wiggle room. This is terrible right? The clang sound accompanies a shift into either direction or even a shift from D-N-D-N. Same with Reverse-N. Please post back and confirm my fears. Thanks again for the help.
#7
10-07-2007, 02:59 PM
RE: Scary noises, Drivetrain clang.
well it def., sounds like a u-joint, u might need to get that stuff checked out
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