Vibration

TrumanDrive · February 20, 2005

Hi all, sure could use the help.

I have a 2000 Silverado ExtCab. 2wd. 80k bought new. I have been experiencing a vibration in the seat and wheel for about 1year now, starting @ appox 35 mph to 50 mph. the worst @ 40. Tires have been eliminated. U-joints have replaced. Driveshaft has been balanced. Motor mounts seem good. Limited slip differential has been replaced.(had been acting up).

I read as many post as I could and seems like a dealer wants to just throw alot of money at a problem like this. I'd like to narrow it down a little with your help.

History of Truck----Tranny rebuilt 2 months after purchase, fuel reg replaced, piston slap, ABS mod shot, launch shudder, slip yoke clunk, wind noise from all windows, one window motor shot, fuel guage erratic, rear differential shot-and GM offered me a coupon to buy another. Other than that I love the truck.

mcreyaufmiller · February 21, 2005

My first thoughts were for the u-joints, even though they have been replaced, check them again. then have your wheels checke for true, I noticed that you eliminated the tires, but again, check the wheels. An easy way to do this is to rotate the wheels, if the vibration stays the same, wheels are out. Okay, wheels and u-joints, next, check the tranny. To do this, while driving shift out of drive into N. If the vibration goes away, then you have a problem in the drivetrain. If it stays, than it is in the chasis somewhere. Sorry for the ramble.

71GMC_3/4T · February 21, 2005

What frequency/speed is the vibration? Fast - buzzing? Tire rotation speed - woggly?

The reason I ask is that I had the same type of thing at a similar speed and it turned out to be a bad idler arm. Crawl under the truck and try to push up/down on the idler arm portion of the drag link and tie rod. If you can move it up and down much, it's bad. Maybe about 1/4" would be acceptable. Mine moved about 1/2" and would shake after hitting a certain bump on the road at 40 MPH. It did this every day in the same spot and about drove me nuts! It was a lower frequency vibration, related to the tire speed. The idler arm is a commonly missed lubrication point mainly because it's a real beach to get to.

TrumanDrive · February 21, 2005

The vibration I would guess as a low Frequency rumble. The vibration is present at those speeds whether I am accelerating,deaccelerating or cruising. It is also present in any gear and in neutral during those speeds. As far as tires go, the vibration is present while the rear end is jacked up, with or without the tires on. I am also assuming this eliminates the front end.

However, you say there is a lub point on the Idler Arm that gets looked over? Is that a zerk fitting and approximately where is it located? Thanks

71GMC_3/4T · February 21, 2005

Use a mirror and flashlight, or drop the skid plate to find the zerk. My '92 was way up in there, but once I knew where it was, I could find it by feel (okay, most of the time...). If you have a 2WD, it should be easy to see, so you may have been greasing it already. It's the frame pivot point for the idler arm.

If you have a 2-piece driveline, check the phase angle. That's the rotational difference angle between the U-Joints and it will cause headaches. Take it to a shop and ask them. If they don't know what you're talking about, go to another shop until they do.

Check your tailshaft in the tranny. Maybe you have a bad bushing that's allowing it to wobble more than it should.

TrumanDrive · February 26, 2005

FIXED

Well, I got it. What a pain. After trying many things including having the driveshaft "professionally balanced", I figured out the speed specific Vibration problem....The driveshaft was not balanced. I ended up with 3 hose clamps and a 10 penny nail at the back of the back shaft. Worked like a charm. I quess I'll be asking for my 80 bucks back.

No dents, scrapes or other signs of abuse but after 75k miles I quess it was just time.

I am dissappointed in the local advise (tranny shops,...ect) in a town of over 100k people. I have come to learn that this forum holds extensive lessons to consider if one takes the time.

I am not looking forward to my next truck problem, but I know where to get help when it happens.

mcreyaufmiller · February 27, 2005

Glad you got it figured it out. Take it back to the guy who balanced it and either ask for your money back or for him to do it right. Glad we could help however little it was.