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Comments
Thanks, Michael
Info - Driveline Clunk #99-04-20-002A
Driveline Clunk
2002 and Prior Light Duty Truck Models
This bulletin is being revised to add model years. Please discard Corporate Bulletin Number 99-04-20-002 (Section 04 -- Driveline/Axle).
Important
The condition described in this bulletin should not be confused with Driveline Stop Clunk, described in Corporate Bulletin Number 964101R (Chevrolet 92-265-7A, GMC Truck 91-4A-77, Oldsmobile 47-71-20A, GM of Canada 93-4A-100) or Bump/Clunk Upon Acceleration, described in Corporate Bulletin Number 99-04-21-004.
Some owners of light duty trucks 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.
© Copyright General Motors Corporation. All Rights Reserved.
"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."
So in other words, there is too much lash in all of their gears. If the above was a certainty, then EVERY SINGLE vehicle would make this clunk!
Which is why I personally don't believe it's lash, unless they manufactured only Silverados with excessive lash.
The clunk on mine comes from the rear of the truck. I think it's the ring and pinion, but who knows?
"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."
Again, the above paragraph points the finger at shoddy engineering tolerances.
At 42k miles, I had to have the rear rotors resurfaced & they are now at minimum thickness. New pads were also needed. Of course, the 1 year warranty on the OEM rotor has expired.
Are others still having brake life problems? I did a search & see some posts from '02 & '03 but nothing came up in this "active" group of posts. Thanks.
2000 xcab 5.3 SB
At approx. 15,000 miles, something similar happened. It was towed to a dealer and was repaired under warranty. They never gave me copies of the work records, something I failed to notice until several miles down the road.
Has anyone else had similar problems with oil pressure? Any ideas? I am about ready to trade for a Ford!
IS IT ANY GOOD?? HAS ANYONE ANY EXPERINCE WITH IT??
I know that the 5.3L V8 is a very nice engine. BUT the truck that is for sale has got the 4.8.
Uhhhh, I sorta need to know ASAP as I gotta make the deal or not by tomorrow afternoon.
ANY info will be greatly appreciated. Thanks much!
Spray on is the only way to go. The plastic drop in will only wear the paint away and allow rust.
What happens if after running for a period of time the oil works through the engine as is should but the valves are letting oil passed as they should not and it sets in the cylinder until the next time you start it. At this time it is burned and you see the cloud of smoke on start up. The oil passing the valves is minor so you do not see a lot of oil usage.
it misses real bad when it is wet or alot of moisture in the air, i have replaced wires, plugs
cap, rotor fuel filter had injectors cleaned, but
none ofthis has helped, runs goodwhen it is warm
or dry , any suggestions
03Z71
My 2004 1500 Z-71 EC SB w/5.3l & 3.73 rear averages anywhere from just under 17 to just over 19 mpg average for 80/20 highway/city driving (obeying the speed limit too, though). The worst tank my 1/2 ton has acheived was around 12.5 and involved lots of idling on the dealer lot as they let the jumped battery charge.. The best involved babying the heck out of it and running ~2 mph under speed limits everywhere. And, just for those that like things a bit faster and drive mostly highway- on the one long trip I've taken with the truck since buying it in October, I averaged 5 mph over speed limits (said limits being between 60 and 75 - so I did between 65 and 80) the whole way, through fairly mountainous interstate routes (traveling from western NC to eastern WV through western VA), and I still averaged 17.5 mpg.
Hope this info is useful to you.
Edit: Forgot to mention that about as much of mileage is your driving style as the truck / engine / tranny gearing. I've seen varying reports for 1/2 tons similar to mine, ranging from maybe 3 mpg less on average up to maybe 1.5 more than I get. My own father (lives in WV, and is who I was heading to visit on that long trip mentioned above) travels mostly rural roads through the mountains in his '04, and he has been complaining about his mileage lately. It seems he averages about 1 mpg less than I get in most similar driving conditions. His truck is VERY similar to mine with only minor equipment differences, paint color, and 16" wheels vs. my 17's, but the same drivetrain and body style.
Of course if you don't have tow/haul or don't want to use it, I'd say a lot depends on how big a load you're pulling, what kind of road (grade, mainly) you're pulling it on, etc. If the truck can maintain overdrive without constantly downshifting then upshifting again, go for it. What's really hard on the tranny is the constant hunting when pulling a heavier load. When that has happened to me in the past (usually on steeper grades) I've always manually selected the lower gear until I got to an area where the tow vehicle could maintain the higher gear again. (My last tow vehicle was a 2003 Trailblazer and didn't have tow/haul mode.)
Where can we find instructions? Diagrams?
email me at alanjones10@cox.net