1999 Blazer - Vibration somewhere in the drive train

I started getting a bad rumble from the rear when I would go over 40MPH and sometimes I could feel it when starting out.

At first I thought it was the tires, so i had those balanced and rotated.
Rumble sound is still there.

The guy at the tire place said it was in the drivetrain.

I can fix allot of things but to be quite honest I don't know anything about drivetrain related problems.

Any help would be much appreciated! i don;t want to get ripped off if I have to take it to a pro.

Thanks,:banghead:
Tony

I had a bad vibration last year. I too thought it was the tires. Balanced them and nothing. I took it to a tranny shop and they checked it out and said that it doesn't sound too good probably something internal. To my surprise the checked the universal joints and that was the problems. Since then no problems. I am betting the universal joints. Good luck

After tires/wheels are balanced (force balance is best - machine checks tire /wheel combo for heaviest areas and if tire is out of spec) then the U-joints and driveshaft. You can have a auto machine change both and balance the driveshaft for about $100. If thats not the rear vibration, look at the rear disc/parking brake drum assembly - mine (2001) were out of round and caused vibration (bad factory casting and rusting). Drove me crazy for awhile. Jacked the rear up, removed tires and bolted the lug nuts on to hold the rotors, then put in gear and idled it - you could see the disc part was round but the parking brake drum section was oval so at 65mph up vibrated/hopped. Thought it was the axles/bearings but Chevys have some play in them. Hope that helps. Watch out cause the shops love to start changing everything till they get it right on Blazers.

Thanks for the info guys!

I should know more after tomorrow.

It's funny you mention the back brakes because this all started after I had to use the E-brake because I was installing a new stereo and I had to put it in L1 to get the dash off.

About an hour later when we went to the mall, I heard "strange" noise come from the rear and on the way home that's when I noticed the shudder from the rear.

Maybe I'm grasping but I am at a total loss.

thanks again!
Tony

Damn, All Blazers have the same problems. I have this same exact problem right now. god damned funny blazers. the u-joints make sense tho. the same thing happened to my celica. never got it fixed. just delt with the rumblings. then 1 day my drive shaft fell off. scarred the holy shit out of me and my passengers. cost me like 15 bucks for new joints and screws i think. that was a bunch-o-years ago. im gonna buy that shit 4 my blazer 2maro.

Took it to the garage today and both U-Joints were bad.


Thanks again for all the help!

Tony

How can you tell if the u-joints are bad?

The one in the rear had visible wear and would not move at all.
The front one was worn out so much it was ready to fall out.

When they had it on the lift you could see the driveshaft wobbling.

Muzzy, the best way to check U-joints is to drive the vehicle about 5 miles. After parking it, crawl under and feel each bearing cap. If any are hot(not warm), the U-joint needs replacing..

I have been following the vibration thread thoughtout the forum. I have a 98 Blazer LT 4x4 loaded. Tow package and Goodyear Wrangler tires P225-75R15 M/S. I primarly drive it long distance, in the winter, in the North East. I have posted before as to my vibration issues and this is what finally fixed the issue: The probelm was when I drove between 65 - 80 the vibration would shake so bad that I thought the shifter would come off. You could fee it everywhere in the truck. I did have the garage check all of the front end components and was told that the truck was in great shape. So back to the solution. I saw you guys changed out the rear brake assemblies. I needed brakes and had thought about selling the car, but gave it one more try. After $1200.00 in a full replacement of disk/drums, calipers and a new e brake sytem, I have to tell you it is like driving a new car. I want to thank all of you guys for all of the sugestion that I was able to follow. The garage did not think that the rear brakes would make that much difference, but I think they are signing up to this forum now.
Thanks

Just joined this forum,..... Hello,..... thank you for having me!! I do a lot of wrench work and have for years. Whenever I encounter a new problem I like to research it out and find what others have to say about it,..... before I dive in!. My wifes 99 LT 4 door blazer is experiencing the vibration problem that you seem to refer to here. The vehicle is maintained in somewhat fair condition. The brakes have been worked on and are in decent shape. The tires are good. Had the local U.S.A Muffler try to address the issue,.... they wern't sure but thought possibly in the drive train. Well,..... that leaves a lot to think about considering it is a 4x4. Ater driving the vehicle with all the windows down,...... and trying to sense the feel of the vehicle,...... I belive that yes it was in the drive train. I thought of course,.... possibly transmission, differentials, transfer cases and of course U-joints. then before I made it home got that sick feeling as little images of dollar signs started dancing through my head!!! Stopped at the local Advance auto and thought,..... ya maybe U-joints,.... only to find out there are two different type of assembilies for the 99 4x4,..... NICE!! So in the drive way after putting the truck in park,..... shifted to reverse and heard the very audible CLUNK. In the old days that would be a dead give away for U-joints. Knowing there is more components in a 4x4,..... not a dead give away,.....!! So with vehicle off,... properly blocked and raised on a jack with jack stand in place,.... I crawled under to find from the front differential there is a shaft that has 1 U-joint conecting there then assembles to a transfer case Forward mid-way of vehicle thinking it is splined in under a boot assembly. Then a much longer drive shaft coming from the transfer case to the rear differential with U-joints on both ends. I placed the vehicle in neutral and put a small C-clamp around the body of the rear drive shaft and rocked everything back and fourth observing the play from front shaft through transfer case and relation to back shaft. I felt a sizeable amount of backlash through the transfer case,..... and,..... I'm thinking,.... this isn't good. I don't know though what is allowable and what is considered too much. I definately could understand that this could be the CLUNK that I encountered. Heres the thing though,..... I'm still going to replace the U-joints because I know they are due,...... I will see if this helps with the vibration and ugly rumble sound I hear. I suspect though the tranfer case may need to be "Tightened up" ,....... any thoughts on this or someone else's experience would be appriciated! When I have gotten to the point where the U-joints have been changed out,.... I will let others know what the outcome is,..... thanks!!:dunno: