Ok, I have a 1990 Ford F-150 4x4 5.0 L. I bought it in September and have had no problems until about 3 weeks ago when I noticed some kind of vibration that seemed to come from the rear end. I looked over the truck myself and found nothing wrong or loose (I am no expert by any means but I am somewhat knowledgeable). So, I took it to two different shops, the first one basically ignored my problem, the second one, the mechanic told me that he look over everything he could think of: engine mounts transmission mounts, and also said that the rear end was tight. Does anyone have any idea what might be causing this vibration? I will be leaving to college soon and really need to find this, besides the fact that I want a reliable vehicle, the sound is very annoying! Any input is appreciated.

 

go to a tire shop and have the balance checked on 'em

 

check your u-joints

 

Thanks, that kind of confirmed what I thought it might be. I called the tire shop yesterday. I checked the u-joints myself and thought they seemed a little loose, but both the mechanics I took it to said they were good.

 

Your drive shaft may have thrown a weight and is now out of balance. If the tires are not the culprit that is another thing to check.

 

I'm not exactly sure what you mean.

 

On the driveshaft there are usually pieces of metal welded on the shaft itself to balance it out (like you would balance a wheel). your gonna notice one missing if one area of the shaft looks like its clean and has no dirt/rust compared to everything else.

You could also have an out of balance tire, get them and the rear checked for play.

 

Could be a bent wheel. My '93 had one when I bought it, my '95 has one now. Vibrates around 50, 55 mph, goes away about 75.

 

check the balance on the tires... then if you can while your there have them do a road force balance. there are a couple variables for the condition you are describing. the first three that come to my head after reading the other posts are either: bent rim, out of balance tire, or the tire has a busted belt. if its in the tire, they will be able to tell with a roadforce balance test.

 

If a tire has a busted belt, you should be able to see it, as the face (tread) of the tire will have a bubble where the belt has busted. If the belt has slipped, you may or may not be able to see it, but it will cause the same result, and you should be able to tell by visual inspection and having them spun on a balancer

 

Ok thanks for all the help, but I have an update on the problem. Last night we got a bunch of rain and I was driving my truck while it was raining. This morning I noticed it was no longer making noise. So, my guess is something was dryed out but I have no idea what. Any ideas?

 

YOU check your u-joints, not your mechanic. Rear-end vibes most often come from u-joint/drive shaft problems...while a bent rim or out of balance tire may be the culprit, those tend to show themselves in the front...also, check the level of the fluid in your rear diff....give your driveshaft a good look-over...wasted rear shocks could also cause a vibration. Keep us posted.

 

I just had the same problem and had checked everything and couldn't fine anything wrong. I decided to just go ahead and change the ujoints. When I pulled the driveshaft, they were a bit loose. After putting new ones on the vibration went away. Pull your driveshaft off and give check your ujoints that way. My vibration started around 55 and was at its worst from 60-65 and was still there til at least 75.

 

Do you have noise, vibration, or both? If everything os OK now, you may have had a glob of mud or something in the backside of a wheel.
Check it at all speeds before you go back to school. I let a U-joint go too long once. Wasted half a day stranded on the interstate, walking back and forth to an auto parts and changing it in the rain.

 

It was both but no its gone. I haven't been mudding recently so I thought maybe something was dry or something. The mechanic I took it to said something about some worn rubber somewhere, but he wasn't specific I thought someone might know what he was talking about so I can keep it oiled so the noise won't come back.