Vibrations at 55-65mph

[L1011tristar17]

Just like the title says. This has only been happening for a week so far. The wheel weight had fallen off of the rear wheels so that one was rebalanced. Lugs are properly torqued and I just added air to all four wheels. I'm not sure what the source of this problem could be. Wheel bearings in the front are both good but I haven't checked the back ones yet.

And if it matters I changed the transmission fluid and filter a few days ago. Given the mileage on the transmission (135,000) I don't know if changing the fluid could have knocked something loose inside the trans.

[gadget73]

Tires out of balance, tires out of round, bent wheel, bad U joints, severely warped rotors, improperly balanced driveshaft (usually a weight broke off). Basically you'll have to start checking things and eliminating possibilities. I'd probably start by jacking the car up one corner at a time and spinning the wheels. Look straight across the tire and see if you see any high or low spots roll by as the tire spins. If thats good, have all 4 re-balanced and see if that helps.

[L1011tristar17]

I'll check on all that tomorrow! I think I can rule out the rotors, since those were replaced just a month ago and there isn't any shaking or pulsating while applying the brakes. I'll check the driveshaft weights since the wheel weight seemed to fall off on its own. What are the symptoms of a bad universal joint?

[Bigbullitt]

My vibration is between 45 and 50 mph. I'm replacing the u-joints this weekend. Trans fluid and filter change as well.

[jaywish]

Vibrations that go away after speed increases are often alignment. Right Scott?

[L1011tristar17]

Just jacked up the car and checked underneath. Driveshaft looks good (no missing weights or marks) and the U-Joints seemed fine too. However, when I had one rear wheel up it had quite a bit of play back and forth (parallel to the rear axle). It was almost as if the lugs weren't tight enough, but I checked and they were all torqued properly. I didn't have a chance to look at the suspension, so I'm not yet sure what's causing that to happen.

[purplebomb302]

Is the vibration happening when your on the gas or off the gas?

[L1011tristar17]

Is the vibration happening when your on the gas or off the gas?

Both. It seems to get a little better with my foot off the gas.

[L1011tristar17]

I don't know if it needs an alignment. With my hands off the wheel the car continues straight and doesn't pull to either side. Unless it's only the rear wheels that need attention.

[sly]

it a tire has a flat spot (locking up the brakes, sitting for long periods) it'll do that... weak shocks will make it more apparent. Give the car a bounce test (stand on the bumper and jump off) and see if the car does more than one oscillation (up over center and rest at center). Good shocks will just return to center and stop. OK shocks will do one oscillation. Bad shocks will do more.

[L1011tristar17]

Shocks are OK (one oscillation max) and I didn't see any obvious flat spots, although I will check more thoroughly later. One thing I did notice on the wheel that was balanced (d/s rear) is that there is a small scrape on the edge of the rim.



Is this scrape enough to mess up the balance of the wheel? It was there before the wheel was balanced again a few days ago, if that matters.

[GM_Guy]

That shouldn't matter. Looks like it has been there for some time anyway. Did you get all 4 wheels rebalanced? You may have lost a weight on another wheel as well. I'd personally start with getting all 4 wheels run on a balancer. Be with them and watch it on the balancer. You are looking for severe wobbles, and quietly you are looking at the readout before and after a re-spin after adding weights for your own peice of mind that they actually did balance the tires to the best their machine can do. (Which really doesn't mean much if their machine has a problem, but you'll likely notice a change in vibration which will confirm wheels and then find another tire shop for another rebalance. Locally, I get the best balance from a hole in the wall used tire shop. The guy is a balance madman. He's also the only guy who's actually gotten stickon weights done to near perfection on a set of wheels I don't want external weights on.

Alex.

[L1011tristar17]

All wheels have now been balanced. The vibration is a lot better now, especially at highway speeds, although it still occurs at around 45mph. Good enough for me I guess. I'll be driving to Charlotte on Sunday and then have job training (Resident Adviser for this residence hall I'll be living in) for the next two weeks, so I won't have time to tear into anything looking for another cause of the problem.

I guess the wheels really needed a good balancing, because I noticed the front two wheel weights had been shifted forward about 10-15 degrees each. I could see the grime marks and outlines from where the weights originally were. I never really got the wheels balanced after I got new tires now that I think about it.

[Bigbullitt]

Mine is when accelerating or not, but a little worse when giving it gas. Vibration felt more like it was coming up from directly underneath the car. I know what tire vibration feels like, and this isn't it. My new u joints are only guaranteed for 50,000 miles and the car has 150,000, and I don't think they've been replaced ever.

I decided to remove the drive shaft this evening, but got stumped by the bolts. I had nothing that would fit. I'll go to the parts store tomorrow. What size is it, anyway? I'd rather learn it from someone here.

[gadget73]

12mm 12 point if memory serves.