Piston Slap: I'm Pickin' Up Good Vibrations Pt. II

Sajeev Mehta
by Sajeev Mehta

Chris writes:

Thank you all for your input on my question. I took the truck to my mechanic and he gave it a good go over and could not find anything wrong. He was said it might be the heat shield on the exhaust system vibrating at that RPM however he could not find anything loose. I did get the transmission fluid changed and everything looked good there. Thanks to you and the readers of Piston Slap for all the good advice.

Sajeev replies:

Loose heat shields make tinny, obnoxious rattles. They can’t cause what you’re feeling. I am a little concerned your mechanic isn’t looking at your specific problem.

The big concerns raised by the Best and Brightest (torque converter, engine mounts and driveshaft U-joints) are hard to diagnose with the truck on a lift. If the mechanic didn’t drive it on the highway, gun the motor while looking at it, etc. you should take it back. Or find another mechanic. Because time is money, and you probably wasted a fair bit of both right now.

That’s my $0.02. Best and Brightest, am I wrong?

(Send your queries to mehta@ttac.com)

Sajeev Mehta
Sajeev Mehta

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  • Obbop Obbop on Dec 09, 2009

    Is it possible that a shop with a dynamometer or other device allowing the free-wheeling of an axle's worth of wheels would assist in ascertaining the source of noxious sounds, shudders, vibrations etc.?? With so many different moving things down yonder it's miraculous there are not more complaints about thuds, groans, squeaks, yawns, groans, clunks, howls, and a horde of various vibrations, some good, some bad, some noteworthy and others grimace inducing. Personally, being a simple creature, I apply what is often the first thing to poke at when electrical/electronic quirks arise.... bad ground. Down below, what contacts the ground? Tires!!!!! Check for out-of-roundness or a bad tread or a defective internal ply or whatever then proceed from there. Perhaps a visit to a qualified tire/alignment place with experienced personnel may be helpful. I take donuts when seeking assistance from the wrench doctors of autodom. Bribery often places personnel on your side, encouraging their endeavors, urging them to exert a few extra calories drawing upon their experience to diagnose your problem and find a cure. A brief mention of appreciation for their experience and efforts regarding what can be a complex subject can be fruitful. Look at society as a whole and where so often the adulation is directed.... entertainment figures, sports stars... the mass media is horrible about this. The "common man" receives short shrift but remove the common workers from the social equation and observe how fast the whole shebang collapses. Get the tech/mechanic on your side, if possible, and you may be on thine way to motoring Nirvana. If not, tray another place, other workers. Donuts are cheap, especially at the bakery outlet stores. A buck for a dozen donuts here in hillbilly heaven. Or is that "haven."

  • Raymond Hieber Raymond Hieber on Dec 09, 2009

    Carrier bearing if I was going to start throwing parts at it.

  • Lorenzo Lorenzo on Dec 09, 2009

    I have to go along with Boombox1, it's most likely a driveline u-joint. I had a 1980 Buick Regal that had the same symptom. It wasn't very noticeable at low speeds, but on the freeway, whenever I was going downhill and let up on the gas, it would vibrate. I took it to a local mechanic, described it, and he said it's probably a u-joint. He put it on the rack and grabbed the driveline near each u-loint and tried to twist it. At the front u-joint near the tranny, the shaft twisted a little, and it was obvious it was the u-joint. He replaced it and I picked up the car two hours later, problem solved, and for very little money. Take it to another mechanic, describe the vibration while coasting/deceleration, and ask him to check the u-joints. There are other possible causes, but that's the most obvious (and cheapest fix), and it should be checked/eliminated first.

  • Eamiller Eamiller on Dec 09, 2009

    I think you missed some TSBs in your last PS question. There are several related to vibrations/rattling like: Make : CHEVROLET Model : SILVERADO Year : 2004 Manufacturer : GENERAL MOTORS CORP. Service Bulletin Number : 04222004 Date of Bulletin : APR 22, 2004 NHTSA Item Number : 10009235 Component : POWER TRAIN:AUTOMATIC TRANSMISSION Summary : RATTLE TYPE NOISE DUE TO A CRACKED FLEX PLATE. GM VOICEMAIL EXPRESS. *TT Make : CHEVROLET Model : SILVERADO Year : 2004 Manufacturer : GENERAL MOTORS CORP. Service Bulletin Number : 3048A Date of Bulletin : NHTSA Item Number : 10017154 Component : ENGINE AND ENGINE COOLING:ENGINE Summary : SUPPLEMENT TO 03-06-01-024B 4.3L LU3 L35 TIMING CHAIN TENSIONER. RATTLE-TYPE NOISE COMING FROM THE ENGINE AT APPROXIMATELY 1800 TO 2200 RPMS. *TT Make : CHEVROLET Model : SILVERADO Year : 2004 Manufacturer : GENERAL MOTORS CORP. Service Bulletin Number : 040601012 Date of Bulletin : MAY 01, 2004 NHTSA Item Number : 10012591 Component : ENGINE AND ENGINE COOLING Summary : RATTLE OR CRACKLING NOISE FROM ENGINE COMPARTMENT. *EH UPDATED 03-07-06. *KB Make : CHEVROLET Model : SILVERADO Year : 2004 Manufacturer : GENERAL MOTORS CORP. Service Bulletin Number : 3105 Date of Bulletin : NHTSA Item Number : 10017226 Component : POWER TRAIN Summary : PING, POP, SNAP OR CLICK NOISE FROM THE PROPELLER SHAFT. *TT Make : CHEVROLET Model : SILVERADO Year : 2004 Manufacturer : GENERAL MOTORS CORP. Service Bulletin Number : 3294 Date of Bulletin : NHTSA Item Number : 10013541 Component : POWER TRAIN:AXLE ASSEMBLY Summary : HIGHWAY SPEED VIBRATION ON SMOOTH SURFACE. *EH Make : CHEVROLET Model : SILVERADO Year : 2004 Manufacturer : GENERAL MOTORS CORP. Service Bulletin Number : 3438A Date of Bulletin : NHTSA Item Number : 10017100 Component : POWER TRAIN:AUTOMATIC TRANSMISSION Summary : TCC SURGE AND/OR FLUID CONTAMINATION. *TT Make : CHEVROLET Model : SILVERADO Year : 2004 Manufacturer : GENERAL MOTORS CORP. Service Bulletin Number : 3260 Date of Bulletin : NHTSA Item Number : 10017145 Component : POWER TRAIN Summary : 4L80E/4L85E HARSH SHIFT OR SLIP NO TCC APPLY. *TT Make : CHEVROLET Model : SILVERADO Year : 2004 Manufacturer : GENERAL MOTORS CORP. Service Bulletin Number : 060417002 Date of Bulletin : DEC 01, 2006 NHTSA Item Number : 10021100 Component : SUSPENSION:REAR:AXLE:NON-POWERED AXLE ASSEMBLY Summary : REAR DRIVE AXLE WHINE NOISE (REPLACE SLIP YOKE ASSEMBLY). *KB Make : CHEVROLET Model : SILVERADO Year : 2004 Manufacturer : GENERAL MOTORS CORP. Service Bulletin Number : 050730017 Date of Bulletin : FEB 01, 2006 NHTSA Item Number : 10017462 Component : POWER TRAIN:AUTOMATIC TRANSMISSION Summary : 4L60-E/4L65-E AUTOMATIC TRANSMISSION/TORQUE CONVERTER CLUTCH (TCC) SHUDDER, WATER IN TRANSMISSION. *TT

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