Vibration At 55 - Sometimes

[natesimpson74]

Hello. I recently bought a 1999 Silverado 1500 nbs with 128,000mi. When I get to about 55mph I sometimes get a harmonic type vibration- vmmmm vmmmm vmmmm sound. I can feel it through the floor board, but my wife says she cant hear or feel anything in the passenger seat. I just had new tires installed, fresh alignment, changed fluids in front and rear diff. I also checked the front end and everything is tight. U-joints are tight. I can't find anything wrong. The thing is that it doesn't always happen, probably 50% of the time. If I speed up it is not quite as noticeable, but I can still feel it a little.

 

I searched through many posts and can't find anything out about what this could be. Any ideas as to what to look at would be greatly appreciated. Thank you.

[natesimpson74]

No one has any idea? How do I know if it is torque converter chatter? Would that set a code? I can't find anything else that it could be.

[T1ME_Killa]

Check to see if it is happening at low RPM like 800-1300 i had the same thing and it was an exhaust issue on my silverado they needed to replace some pipe if you would like ill contact the dealer that replaced it and see if their is a recall for you

[T1ME_Killa]

i can still feel it a little from the steering wheel and the pedals

[natesimpson74]

Check to see if it is happening at low RPM like 800-1300 i had the same thing and it was an exhaust issue on my silverado they needed to replace some pipe if you would like ill contact the dealer that replaced it and see if their is a recall for you

 

If you could find out if there is a recall or TSB I would appreciate it. It is at lower rpm like 1500-1700 or so I guess. It pretty much happens after TC lockup.

[T1ME_Killa]

the service dpt is closed in my town now but i will get an answer as soon as i get up tomorrow

[txab]

Maybe driveshaft balance needs to be checked

[T1ME_Killa]

Hello. I recently bought a 1999 Silverado 1500 nbs with 128,000mi. When I get to about 55mph I sometimes get a harmonic type vibration- vmmmm vmmmm vmmmm sound. I can feel it through the floor board, but my wife says she cant hear or feel anything in the passenger seat. I just had new tires installed, fresh alignment, changed fluids in front and rear diff. I also checked the front end and everything is tight. U-joints are tight. I can't find anything wrong. The thing is that it doesn't always happen, probably 50% of the time. If I speed up it is not quite as noticeable, but I can still feel it a little.

 

I searched through many posts and can't find anything out about what this could be. Any ideas as to what to look at would be greatly appreciated. Thank you.

 

GM Document ID:2060205

Bullion number :020605003G

 

if it is what was wrong with mine they will need to install a flex coupling.

 

Ask your dealer about part number 15076928 if you have a 4x2

Ask your dealer about part number 15076990 if you have a 4x4

 

ill post the actual document once i get to work

[natesimpson74]

Thank you for the info. I am getting the feeling it is torque converter chatter though. Not real sure, I am going to add some trans lube to the trans fluid and see what happens.