Hi folks,

I just bought a 2001 Blazer LS (2D/2WD) with about 18000 miles on it. The car is immaculate and its history checks out. It's perfect except for one thing -- a really annoying, intermittent vibration at highway speeds above 65-70 MPH.

It is a fairly intense vibration that shakes the whole car. I do not feel it much in the steering wheel -- it mostly seems to be felt throughout the vehicle. It varies in intensity, and I sometimes think I can feel it at low speeds (30 or so) ... but not much. The vibration seems to happen less in cold weather. This weekend the temperatures dropped and it was noticeably better.

The tires have been balanced, rebalanced and then replaced (and balanced) with Goodyear Radial T/As. It has been checked and aligned. Transmission mount is good. Suspension looks fine and shocks are all right. Wheels are round and do not have any damage.

The dealer's service manager showed me a TSB that indicated some of these trucks have a vibration at 60 MPH, and indicated that I should just deal with it because it's just something that happens with these Blazers. I want this fixed.

Anyone have some advice for me? This is my first time posting here, and I could really use some help. :-)

This message has been edited. Last edited by: jbayless,

poss drive line is bent or if the vehicule has been modified in any way with the drive train then thats the problem. some people lower there cars and then forget to adjust the tilt of the rear end that will cause a vibe because the angles are not right.ill just bet its the drive line angles are not right. or i could be really wrong and the front end is in bad shape (ie its hit a lot of pot holes ect so the ball joints are loose ect.

adding to dodges reply
Could be a loose suspension unit or a bush on the suspension unit which is at the end of its life Only way to check for it is to measure the ride height on Level ground from the ground to the top of the wheel arch (only be a fraction of an inch) or.. Jack the Vehicle up onto axle stands Then rock the front wheels from the top and bottom If there is any play the bushes need renewing (Cheap to buy but a few hours work to replace) also any side play may be steering box mountings? No movement then drive coupling or drive shaft damage is my best guess.

PS if it had been a really old car I'd say worn or dry Kingpins AKA Swivel-pins ( Raplacement Job Home mechanics hated)

just reread the question and when you said it improved

quote:

The vibration seems to happen less in cold weather. This weekend the temperatures dropped and it was noticeably better.

Thats Driveshaft ! You'll find 1 or both of the Driveshaft sleeves will be distorted or the Coupling ?
Somebody has overloaded the transmission on an occasion and the result is this damage ...Another clue maybe a soft "clonk" sound on takeup of drive. Try doing a "reverse-drive-reverse" rocking motion quickly (as if you were stuck in mud. You may hear it louder ?Only have to drive a foot or so Use only enough gas to make it creep !

Thanks for all the replies!

There is no clonk on takeoff ... the U-joint has been checked and the steering (ball joints, etc.), have been checked by a front-end specialist that I really trust.

I will rock the truck back and forth a few times before I go to work, and see if I can make it make that sound, just to be sure.

Bedstar, when you refer to the driveshaft coupling, are you talking about the "high-velocity boot" that goes around the end of the driveshaft and balances it, or the U-joint? The driveshaft has been checked out and it appears to be fine. However, I have been thinking about paying to balance it anyway, just to see if that fixes the problem. AAMCO told me there was some minor play in the "high velocity boot," but probably not enough to cause this problem.

My thinking is that this problem was with the truck from the beginning, but the previous owner never drove on the freeway enough to notice it. The vehicle still looks like it is new, and everyone who looks at it tells me the mechanical systems are fine.

The previous owner of this truck was 75 years old, and did not drive it much -- it just has 18K miles on it now. In reviewing the service records (it was purchased and serviced at the same dealer where I bought it), I found the last time the previous owner took it to the dealer for an oil change was in 2002, and it already had 7500 miles on it then. That makes me wonder if it sat for a while, and this could be related to it sitting unused.

Okay, I tested it this morning ... it is smooth when rocking back and forth and there is no audible clonk.

I have read of other people having a problem with the drum for the emergency/parking brake on these vehicles. Apparently sometimes it is oval instead of round. Would that cause this sort of vibration?

I checked you car here the see if there was any "Official" recall. Nothing noted on yur problem.

Auto Recalls

Other folks may like to check the own cars to see if their were any recalls.

Only thing I can think of now is an "out of balance" Drive shaft? Has it got any weights welded to it ?(about the size of a cigar butt)
May be evidence of one that was fitted and broken off? (weld splatter)Though with all the road muck you'll have to wire brush the component to see anything

The driveshaft has no evidence of weights on it. However, it apparently has a type of self-balancing boot on the end that takes the place of weights. Right now, I am leaning toward having that boot removed and replaced with weights.

i have not seen any self balancing drive shafts yet. if the parking brake is part of the drive shaft then it could be assumed that it was driven with it on and that would indeed get hot and put it in a non oval shape witch would explain the out of balance.
that boot on the drive shaft sounds a lot like a dust boot.if its secured then you do not wont to cut it or tear it. looking back at what you said (it belonged to a 75 year old man) he very well could have driven it with the parking brake on that will warp the drum and cause the vibes

My bad - I probably garbled the bit about the parking brake.

I *think* the parking brake is a drum mechanism on the right rear wheel. I am going to take the car to the shop tomorrow morning and have them check it out.
The "boot" I was talking about is a cylindrical metal and rubber assembly that covers the end of the driveshaft closest to the transmission.