Should pertain to many vehicles on this site. I have a vibration that occurs at 45mph and again around 70mph. Thing is, not even minutely felt in the steering. Just in my*****. I’m not going to try and troubleshoot this issue on the HAMB, but was thinking of a rotating thing that was once fine and now isn’t. Thanks.
If it was "once fine, but now isn't", I would check the u-joints. While it can happen, very rare for driveshafts to lose balance weights unless it got damaged by hitting something.
There’s tires, U joints. And then there’s ride height changes. Either re arranged items, payload, or suspension that all translate to pinion angle and ultimately Ujoints. Tires and U joints start new and enter a path of constant decline towards failure.
Good point. Always figured it was a tire issue and (don’t laugh please) first time I had an urge/need to exceed the speed limit in a long time. That’s when I noticed the 70 mph***** shake. Edit: on the tires, rotate them now and then front to back, not a hint of a balance issue via wear. Time to crawl under it it and do some shaking and prying. Thanks
Yes on the pay load, have pulled a too big of a tongue weight trailer I have too many times. Makes perfect sense.
Does the drive shaft have a slip yoke that slides on the shaft? If so and it's been removed for repair, it must be put back exactly where it was. There is normally a mark on the shaft/yoke for balance position . Just a thought. U-joints are usually the culprit for unexplained balance issues when nothing has been touched to cause it. Have you changed the clutch lately? That could be the problem. Not knowing what car you have is like looking for the needle in a haystack.
You need to try and figure out the frequency of the vibration. Things that are out of balance tend to vibrate once a revolution. Low frequency vibrations tend to be wheel/tire related. Driveline vibrations are a much higher frequency since the driveline rotates at around 3 times as fast as the wheel ends. Engine vibration is in the same range as driveline in high gear but will be felt at lower speeds in the lower gears. One way to eliminate the engine as a source is to note the rpm at 45 mph (your stated vibration speed) and rev the engine in neutral to that rpm. FYI, vibrations that occur at one speed and then again at a higher speed tend to be tire related.
Might try putting it on a 2 post lift and running it with tires off the ground to see what happens. Switch tires around and/or remove them completely. Might be able to see something vibrating or moving funny.......may want to put a jack under the rear to keep appx ride height. Sometimes belts move around in tires if they are defective. I had that problem once many years ago.
From your description I would first suspect a rear tire problem. If you rule that out check to see if you have a worn (loose) u-joint or possibly a u-joint that is seized and hard to move. Easiest to check with the driveshaft out of the vehicle. Before removing the shaft, if you can run it in gear, up on a hoist, and watch the front end of the driveshaft where it plugs into the transmission. If the rear trans bushing is loose the front end of the driveshaft can spin off-center, creating a vibration. My '50 ford was like that when I bought it and a new bushing and slip yoke fixed that problem very nicely. You could feel excessive wear between the yoke and bushing by hand when it was shut off and stopped.
Thanks all. I attributed this issue at 45mph several years ago to the tires. I lived with it as the tread wasn’t worn yet, never had the time to get them balanced (new job, etc). Two years ago I bought a new set. Soon after the 45 mph seat rumble began. On the way home from work this morning was the first time in a long time I hit 70mph. I just don’t have a need or a want to exceed the speed limit. I’ve flipped the tires a few times front to back, they all look/feel like rear tires, not a cup, different wear pattern, etc. It’s a 1 piece driveshaft. The reason I don’t mention the year/make is it’s OT, but figured it would be okay since it’s relevant to a majority of vehicles here. There’s nothing exotic about the truck (in my mind) that wouldn’t pertain to a 55 Chevy ie. FWIW, the engine doesn’t have a hint of vibration at any RPMs with no load on it. Thanks all. Will crawl under it this weekend. No lift available, jackstands too sketchy to run it in the air, hate to have a 45 MPH hole shot occur
If the driveshaft is dented, it’s bent and the only way to properly repair it is to re-tube the driveshaft. Dented and bent drivelines also can not be balanced. Most guys do not realize how fragile drivelines are. If you clamp a driveline in a vise to remove a u-joint, it’s now bent.
Let’s add to that Not sure why the shaft would be clamped in a vise, but every Ujoint I’ve replaced, I use couple of sockets and a vise for my press to remove and install them. I don’t know how it could be done with the business end sticking out in the air?
Mike Go through all the Free "processes of elimination" First , swap your tires front to rear [if they are the same size] and see if the vibration goes to the steering Then check U-joints and front pinion bearing for up/down movement. And also check the rear transmission mount [these perish] If your vehicle has a Torque Arm or Ladder Bar have you changed the ride height? Check the pinion angles Sometimes spacers under the crossmember [to lower the trans] or under the rear mount [to raise the trans] can remedy this
Set the trunnion of the u-joint on top of the vise jaws. Set the other end of the shaft on the bench. Tap on the yoke, and only the yoke, and drive the u-joint cap upwards. Rotate the shaft 180 degrees and repeat the process. It helps to remove the grease fitting from the cross first. Mike, I’m sorry, I wasn’t clear, never clamp the tube of the driveline it a vise. Your method of using your vise as a press is perfectly fine. Some of the drivelines I work on can be 5 feet long, 4-1/2” diameter tubing with a tubing wall thickness of .259”. These get heavy quickly.
A car can be raised and set on some tires and wheels laid flat under the vehicle and makes a very safe and solid platform.....if you have extras laying around. Since you replaced the tires and got the same result as the first set, I'd look elsewhere for the problem......assuming the tires were balanced properly.
I had a vibration issue in one of my old trucks. Went through all the steps of visual inspection, swapping tires around, replaced the carrier bearing, new output seal. Still vibrated at 30mph and 65mph. I took the driveshaft to a shop to have it balanced, then I tossed new u-joints in, still had the vibration. I had a new ring and pinion set waiting to be put in, so I took the opportunity to do it at this time to eliminate this being a differential issue and found one of the axle shafts was twisted slightly near the bearing end. I barely caught it while wiping down the axles before reinstalling. I ordered a new $78 axle shaft, pressed on new bearings and threw some new seals in and the vibration was gone. I've pulled axle shafts out that were twisted on the splined side and never had vibrations, so that twist on the outer side of the axle shaft was a first for me.
I chased what I was sure was a driveshaft vibration in my 54 Chevy. After trying everything I could think of, it dawned on me that the brake drums also rotate and could be out of balance. Checked them on a bubble balancer and sure enough, they were. Got a new pair, checked and installed them, problem solved. Old drums sometimes sling off the welded on weights.
Thanks, no drums on this truck. No motivation today after 5 night shifts, was going to mow the pasture tomorrow, but it’s full of water right now, so will roll under the truck with a prybar and see what up tomorrow.
The Jalopy Journal
