got the vibe!

Cook · February 14, 2007

whats going on guys? im new to the forum. just picked up a 2003 Silverado 1500 4.3L auto 2WD with 30K miles. im getting a vibration around 40mph @ 1500rpm. basically when it goes into the overdrive gear. the vibration is felt through the floor and pedal, not the steering wheel. if i take it out of overdrive, let off the gas, or give it more gas, the vibration goes away. its completely fine on the highway at all speeds. its really weird, not sure if its the torque converter, transmission, driveshaft, rear end, etc?

looking under the truck it has a new wheel bearing assembly on the drivers side, new u-joints, and new brakes (rotors and pads front and back)

any ideas?

thanks guys

-cook

bobcat5544 · February 14, 2007

Tell you the truth, I could guess all day on this and be wrong. With out feeling it for myself and doing some more test it's hard to help you out. There are so many posibilities.

JRW791 · February 14, 2007

I had the same problem with an '06, 4.3. Took it to dealer for warranty service. Service rep ask me if it was a 4.3 before I could finish describing problem. They cut a section out of tailpipe and inserted a stainless steel flex pipe. Vibration gone!

Cook · February 14, 2007

I had the same problem with an '06, 4.3. Took it to dealer for warranty service. Service rep ask me if it was a 4.3 before I could finish describing problem. They cut a section out of tailpipe and inserted a stainless steel flex pipe. Vibration gone!

wow no kidding, thanks guys! where abouts did they insert the stainless steel flex pipe? got any pix?

thanks again

-cook

bobcat5544 · February 14, 2007

Document ID# 1894053

2006 Chevrolet Chevy C Silverado - 2WD

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Subject: Exhaust Moan/Vibration Noise (Install Exhaust System Flex Pipe Kit) #02-06-05-003F - (01/31/2007)

Models: 1999-2007 Chevrolet Silverado 1500 Series Extended Cab or Regular Cab/Long Box Pickups (Classic)

1999-2007 GMC Sierra 1500 Series Extended Cab or Regular Cab/Long Box Pickups (Classic)

with 4.3L Engine (VINs W, X -- RPOs L35, LU3) and Automatic Transmission (RPO M30)

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This bulletin is being revised to add the 2007 model year (Classic Models). Please discard Corporate Bulletin Number 02-06-05-003E (Section 06 -- Engine/Propulsion System).

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Condition

Some customers may comment on a moan or vibration noise at low vehicle speeds between 900-1200 RPM under load.

Cause

Exhaust system resonance that is transmitted through the powertrain mounts into the body may cause this condition.

Correction

An exhaust system flex pipe kit is available to correct this condition. If diagnosis leads to this condition, install the applicable exhaust system flex pipe kit listed below using the following procedure. Refer to the Parts Information for kit applications and usage.

Important: This fix and the kit part numbers are specific to vehicle frame type. A Level 3 frame was introduced interim 2000 model year (approximately January 2000). With a Level 3 frame, the transmission crossmember was moved forward of its previous location. Pre-Level 3 frames will require the installation of additional components to correct the condition.

1999-2000 4WD Models Built Prior to 1/20/00 and All 2000-2007 (Classic) 2WD and 4WD Models Built After 1/00

These models only require the installation of a flex coupling. The flex coupling has adapter sleeves for the installation of U-bolt clamps. This procedure uses the U-bolt clamps, but the preferred installation method is to weld the flex coupler to the exhaust pipe.

Raise the vehicle.

Locate the first available straight section of pipe rearward of the mid-joint flange and forward of the muffler assembly.

Measure approximately 228 mm (9 in) on the straight pipe and mark.

Using a suitable cutting tool, cut out the marked section of the pipe and remove.

Remove any burrs, if necessary, before installing the flex coupler pipe.

Install the flex coupling (1). Expand the sleeves of the flex coupler, if necessary, to properly fit over each pipe end. The centerline of the installed flex coupling should run parallel to the straight section of pipe (no bends in the coupling) for optimum performance.

Install the U-bolt clamps (2) on each sleeve end of the flex coupling.

Tighten

Tighten the U-bolt clamps to 30 N·m (22 lb ft).

Lower the vehicle.

1999-2000 2WD Models Built Prior to 1/00

These models will require the installation of a flex coupler, two Y-pipe support brace rods w/integral U-bolt clamp assemblies on the LH and RH sides of the transmission rear mount and new transmission mount studs and nuts. The Y-pipe support braces are used in combination with the flex coupler to reduce exhaust moan.

Install the flex coupler using steps 1-7 of the above procedure.

Support the transmission with a suitable adjustable jack stand.

Remove the two bolts and nuts from the transmission rear mount.

Position the transmission rear mount and install two new studs to the mount.

Install the new studs supplied with the kit to the transmission mount.

Loosely position the Y-pipe support braces w/integral U-bolt clamps (LH and RH) to the underside of the transmission rear mount and the crossover pipe as shown. The top ends of the braces attach to the underside of the transmission rear mount. The bottom ends of the braces attach to the crossover pipe using the integral U-bolt clamps. The braces support the LH leg of the Y-pipe where it crosses over the vehicle to meet the Y-pipe collector.

Install the two nuts to the transmission rear mount and the two nuts to the U-bolt clamps.

Tighten

• Tighten the new transmission mount nuts to 25 N·m (18 lb ft).

• Tighten the two U-bolt clamps to 30 N·m (22 lb ft).

Lower the vehicle.

Parts Information

Part Number

Description

Usage

15076982

Exhaust System Parts Package

1999-2000 2WD Models Built Prior to 1/00

15076990

Exhaust System Parts Package

• 1999-2000 4WD Models Built Prior to 1/20/00

• All 2000-2007 (Classic) 2WD and 4WD Models Built After 1/00

• Kit P/N 15076982 includes a flex coupler, two support brace rods w/integral U-bolt pipe clamps, two U-bolt pipe clamps (for use with flex coupler) and two new transmission mount studs w/fasteners.

• Kit P/N 15076990 includes a flex coupler and two U-bolt pipe clamps.

Cook · February 14, 2007

thanks guys! mine is a single cab short bed, think it makes a difference?

JRW791 · February 15, 2007

thanks guys! mine is a single cab short bed, think it makes a difference?

I have a Regular cab with short bed as well. I'll get you a photo tomorrow. The flex pipie did not cure the problem completely but there is a 90% improvement.

ericrlong · February 15, 2007

Tell you the truth, I could guess all day on this and be wrong. With out feeling it for myself and doing some more test it's hard to help you out. There are so many posibilities.

My logic says that your exhaust system is not hung correctly. It may be touching another body or frame part or not suspended by a rubber hanger.