Driveshaft U Joints

[Magic Al]

Have a bad vibration in the car. Occurs in neutral as well as in gear. Slightly less under accelleration, worst coasting. Figuring it's my rear U-Joints.

Recall reading that these were no longer avail, yet Rock Auto lists all kinds of these. My question is whether the rear 2 joints (the "crosses" w/ bearings) are the same as the front one.

I don't want to buy the whole cardan joint, just replace the pieces. Am I looking @ the correct thing? Thanks.

[Hizhonor]

Have a bad vibration in the car. Occurs in neutral as well as in gear. Slightly less under accelleration, worst coasting. Figuring it's my rear U-Joints.

Recall reading that these were no longer avail, yet Rock Auto lists all kinds of these. My question is whether the rear 2 joints (the "crosses" w/ bearings) are the same as the front one.

I don't want to buy the whole cardan joint, just replace the pieces. Am I looking @ the correct thing? Thanks.

Al, if there's a vibration in "neutral" , then it can't be the U-Joints. Check your tires for abnormal wear on the inside and outside tread (steel belt popping through) and check the tire's sidewalls for a bubble. Vibration usually means wheel out of round, front end out of alignment, etc. You could have thrown a wheel weight, too. Check E-Brake for binding, too. One more thing comes to mind ... vacuum leak. Check all the hoses under the hood, especially the one going to the MAP Sensor.

[fury fan]

Are you feeling the vibration more in the seat or the steering wheel? Steering wheel is usualy indicative of the front of the car, while the seat suggests the rear of the car.

To expand on what Hizhonor said:
Why couldn't it be the U-joints? The loading on them changes when going to neutral, of course, but they are still spinning at road speed. Depending on how bad a joint is worn, I think it could still be felt in neutral. At the very least, I wouldn't rule them out without inspecting them, and driveshaft removal is easy enough to justify it. In the past I've found worn joints that felt tight when pried on with a screwdriver when the shaft was in the car, yet had definite notchiness when the shaft was removed and the joints 'swiveled'. Remove the shaft and check them and you may find a 20% contributor to the problem -- or you may find they are A-1 and you can sleep better at night. Remember that the tailshaft area will leak while the shaft is out, so put a drainpan under it. Having the rear of the car higher than the front helps, of course.

One sure-fire indicator of a bad tire/wheel is a slight wobble in the whole car when slowly pulling up to a stop. A wheel imbalance usually shows up as a vibration at highway speed. However, if you have time, pull all 4 wheels and inspect them carefully. Roll the tire for about 20 feet (make sure you make a full revolution) and look at the tread depth across the width of the tire and also along the circumference. The tread depth should be uniform, especially around the circumference. Variations side-side could indicate an alignment problem (which usually doesn't give vibration unless it's extreme) but a circumference variation means you have a broken belt. As Hizhonor mentioned, if you have a bubble on the tread the belt is badly broken (although all broken belts are bad!!!).

Run the engine slightly above idle during your diagnosis, both in gear and in neutral, to determine whether a vacuum leak is a contributor to vibration. I've never had a vacuum leak cause a vibration in a carbureted car, however an EFI car that has IAC with feedback could be a different animal in this regard.

[Magic Al]

Well I took the car to my favorite mechanic, & today they called to tell me it was loose driveshaft bolts. They checked the U-Joints as long as it was on the rack, & all were well. Tightened the driveshaft bolts & it's good again.

Assures me again I have an honest place working on my cars. They could easily have sold me new U-Joints or tires. This cost Less than 50.00 Now why would those bolts have worked loose @ 203,000 miles?

[JBLSC]

my bolts get loose all the time..even with locktite idk wtf it is but luckely i have a lift and its on there every couple of weeks so i go over it and make sure there tight...noticed some bad vibrations last month...got it on the lift and sure enough...bolt was gone haha

[gadget73]

my bolts get loose all the time..even with locktite idk wtf it is but luckely i have a lift and its on there every couple of weeks so i go over it and make sure there tight...noticed some bad vibrations last month...got it on the lift and sure enough...bolt was gone haha

Sounds like you need new bolts and/or a new driveshaft flange. I'm thinking the threads are worn out. They shouldn't come loose like that. I've always had a hell of a time getting the driveshaft bolts loose in anything I've worked on.

[demonswede]

As we are here - what to expect - will the Spring & Ball go bad before the rear u-joint(s).

On my car with about 55,000 miles on + 20 years it did - it was a slight ticking sound & when swapping the U-joints & ball & spring - there was no grease in the spring & ball section & bearing there was bad.

[Leo Cormier]

I just installed new universal joints in my '95 Town Car and I noticed that the flange bolts were Loctited at the factory. I had a rough time getting them loose, but the job went OK. I reinstalled the Loctite when I put it back together. That should prevent them from loosening up.

Leo