newbie vibration question

hi everybody! i am new here, i just got a 2000 blazer lt 4x4. i am noticing some very subtle but annoying vibration that sounds like it is coming from the rear end, however i can feel it a little bit in the steering wheel too. it only starts when i hit 40mph and go from there. the weird part is, its worse at 40mph then gets less noticeable as i go faster. there is no moaning or howling like a wheel bearing usually does, just a steady vibration whose sound kinda resonates through the whole truck, like a very low-pitched humm. could this still be front wheel bearings? i replaced the driveshaft rear u-joint but not the front one, could this be a cause as well? any and all help would be greatly appreciated, this is annoying me because i thought these trucks were supposed to have really smooth rides. thanks!

hmmmm...

First thing I would have said was rear u-joint.

Odd that that wasn't the problem.

Could be the front one. or the driveshaft is out of balance.

how hard is it for the home mechanic to change a front u joint? do i need any special tools or anything?

The front one is a pain and you will need a torch to melt the nylon asembly to get it out.

I would spend the 100 bucks and have a shop do it. They have all the tools.

hmm ok, but you are definitely thinking front u joint? anything else that can cause vibration? cuz i know the driveshaft is balanced correctly. thanks for the quick replies :)

Before anything I would have the tires checked out for balance and for proper pressure.

32psi cold.

oh yea i forgot to mention that, i just had new tires put on and balanced and a front end alignment done. it definitely feels different than tires out of balance too, its a different kind of vibration. i just wish i could describe it better or you could take a ride in my truck :(

I would have the front u-joint checked before you replace it.

If it moves freely, it is fine.

If the vibration just started after having the tires put on, suspect the tires first. Move the rear tires to the front and see if the vibration changes. Possible bad tire, the balance is off, or a rim is bent.

well we changed the u joints and still doing it, any more suggestions? what kind of rear wheel bearings does the 2000 blazer have, hub and bearings or can the bearing itself be replaced?

Sounds like a weight may have fallen off a rim. My uncle owns a tire shop and it's a common problem.

tires have been balanced twice already, problem hasnt gone away. definitely not tires... any other ideas? how easy is it to change rear wheel bearings?

I have the same problem. My moaning noise starts at 50mph now. I'm thinking it's either wheel weights or bad bearing. I' doin some research on the rear bearing now.

awesome let me know what you find out about the rear bearing, i cant possibly find anything else wrong with this truck... could it be the front u-joint on the rear driveshaft too though? because i do get a clunk when i put the truck from reverse to drive, and i have seen people talking about that on here when they have bad u joints that it makes that sound... help!! :(

You might want to look into a bent axle if you've been in any sort of accident. I think I get slight road noise from the front passenger side of my jimmy from that.

I've seen documents where people say park to reverse clunking is normal on 4wd vehicles, I've also read that it is not normal. Go figure.

I'm planning on going to a shop and have them look at it. I just don't want them to poke, play, and charge me if nothing gets fixed.

If you haven't already, check the front u-joint of the rear drive shaft. Also check the amount of play the front yoke has in the transfer case. Could be a worn bushing. If all else fails, carefully put the vehicle on a lift or jack stands, run it, and look for the vibration.

the front u joint is the ONLY thing i have not replaced yet, that can cause vibration? i do hear a clunk when i shift from reverse to drive, and it sounds like its coming from right under me, which would probly be the area of the front u joint. if you guys think this can cause vibration, i will definitely have this replaced

the front u joint is the ONLY thing i have not replaced yet, that can cause vibration? i do hear a clunk when i shift from reverse to drive, and it sounds like its coming from right under me, which would probly be the area of the front u joint. if you guys think this can cause vibration, i will definitely have this replaced

REPLACE IT!

I just posted this in my other thread, but if I coast at about 10-20 mph then let off the gas I get a clunk from my driveaxle. Does yours do the same thing? I'm pretty sure it's u-joints.

I just posted this in my other thread, but if I coast at about 10-20 mph then let off the gas I get a clunk from my driveaxle. Does yours do the same thing? I'm pretty sure it's u-joints.

Sounds like U-Joints. When going from reverse to forward, a loud distinctive clunk is a dead give-away that the U-joint(s) are shot. If they've never been replaced before, you'll have to melt the plastic to get them apart. But you'll probably find that you have a dry socket, meaning the needle bearings have all turned into rust. If you need more instructions, post back.

More instructions would be nice, though I have the basic idea because I have a Haynes manual.

At this point I'm trying to decide whether it's something I can fix or not. Right now I'm leaning towards having someone else do it.

More instructions would be nice, though I have the basic idea because I have a Haynes manual.

At this point I'm trying to decide whether it's something I can fix or not. Right now I'm leaning towards having someone else do it.

You'll need some basic equipment and tools. A torch of some kind, and a 6" vise or press. One of the small hand held propane torches will do, and I have seen a large C-Clamp used instead of a vise.

Basically, you pull the drive line out of the truck and heat the yoke with the torch until the plastic melts that holds the U-joint caps in place. Once enough of the plastic squirts out of the small hole in the yoke, the bearing cap will pop, and you can usually finish removing them witha ball peen hammer. Repeat this for all 4 caps on the u-joint caps.

Buy the U-joints in advance and get the type that have a grease fitting in them. Then, You carefully press in the new caps/U-joints, taking care not to disturb the needle bearings inside the caps. Usually depending on the type, the new U-joints are held in place with snap-rings or horse-shoe shaped clips. If you're not comfortable doing this, you might let a garage do it the first time and see if they'll let you watch so you'll know the next time. :smokin:

Geez, you make it sound so easy.

I'm sorry if this is a stupid question, but is there only one joint in the rear driveshaft and one in the front (for a 4x4)?

Geez, you make it sound so easy.

I'm sorry if this is a stupid question, but is there only one joint in the rear driveshaft and one in the front (for a 4x4)?

The main driveshaft has a u-joint on each end. Not sure about the front driveshaft, never owned a 4x4.:)

There are no stupid questions! :grinno: U-Joints can be easy, but can also be a real PITA! :iceslolan

There are two u-joints in the rear driveshaft, one at the rear axle, the other at the transfer case. The front driveshaft has one u-joint at the front axle.

Have a shop do it.

Will cost 50-60 and they will have the tools to do it properly.

I just posted this in my other thread, but if I coast at about 10-20 mph then let off the gas I get a clunk from my driveaxle. Does yours do the same thing? I'm pretty sure it's u-joints.
yea mine does the same thing almost, except mine does the clunk when going to accelerate again after coasting like that. its not that loud, but you can hear it and it doesnt sound like something that should be happening. i am gonna go have my front u-joint taken care of within the next day or 2, i hope to god this fixes the problem because i love this freaking truck and i have tried everything just to get a smooth ride out of it :( thanks everyone for all your help and for making me feel so welcome on this forum!!! :)