I got a 89 Ford F150 5spd manual. I noticed yesterday I got a vibration whenever I go 55 and faster. Anything after that you don't feel a vibration. I checked my tire pressure and noticed the left rear only had 20 psi when it should have 50 psi so I put air in the tire and it still does it. I'm thinking the driveshaft or the rear end is about to go out. What do you guys think?

 

Shake the U-joints and yokes by hand. Have a tire store look for the leak in the left rear tire. They may discover the tire has cord separation and cannot be balanced. Jack up each wheel and check the wheel bearings by shaking the wheel and rotating it slowly to feel for drag. It seems that the rear end would whine if it was going out. A drive shaft could have been "twisted" if you were abusing it. That would cause a vibration, and would not be visible.

 

I just had to go fill up the rear tire again, it went down to 45 and should be at 50. I filled them all up a couple weeks ago and the others are holding 50psi just fine but the left rear is losing air. Wouldn't surprise me if the driveshaft was twisted cause I had two loads of snow in it during the winter when it snowed and I helped some people move and she was loaded pretty heavy each time! I do know though the brake drums on the rear had got stuck on the truck before but I don't think that would cause the vibration, I do know whenever it rains hard the brake and rear abs light comes on and stays on and I just replaced the rear abs sensor. I should of bought a Chevy/GMC!

 

well, I'd bet it's either the U-joints going bad, or the rear-end was a bit stressed.

When you have uneven tire pressure on your main drive-tires you'll create a difference in speed between the two sides, this will cause the little spider gears inside to spin more than they should - this spinning can (and will) break down the fluid in the rear end. If I were you, I'd change your rear diff fluid, and inspect/grease your u-joints. Make sure you get a tube of "friction modifier" for the rear end - (I use EquiTorque ... not sure of the spelling you can get it at Pep Boys, Checker, Schucks, Kragen, Autozone, Car Quest, Napa or whatever other parts store you've got available) add the modifier to the rear end BEFORE filling with fluid - they say you only need it with limited slip rear differential, but I find it makes ALL differentials run smoother. I also only use synthetic in the rear ends, it holds up better to the type of abuse I can deliver.

--Dave.

 

One of the simplest and cheapest things to check, get your tires re-balanced. Do all 4 of them and like Larry said, get that 1 one that is leaking taken care of and then see what happens. Do you feel it in the steering wheel or just in general? Could be a tire that has worn funny. I have had trucks where the tires started cupping out and it would vibrate like crazy while others wouldn't vibrate. Some out of balance that you could barely feel and others that vibrated like crazy.

My wife's Fusion has a small vibration but I have yet to track it down. Don't feel it, but you can hear it. We had just rotated the tires and when your doing between 15 and 30 you can hear it. We are thinking it could be the tranny starting to act up, my brother's F-150 just lost it's tranny 3 weeks ago at 38K.

 

Rain is one thing, but the ABS sensor can react to a bad wheel bearing or hub. Jack it up and check them out.

 

I appreciate this ALOT! I feel it somewhat but I can hear it. At first I thought it was the drive shaft but I picked up speed to about 65 and it still did it. It didn't get any worse but it does start at 55, anything under 55 and it runs just fine. I only had the truck since january and not sure when the rear end fluid was changed so I better do that and get some grease for the u-joints as well. I'm about ready to get rid of it anyway for a newer truck. But I want to get the kinks out of it before I do!

 

Mr. Ford ...


sounds like cupped tires - if you can hear it, but not feel it, it's most likely in the rear. This could be due to a bad alignment on the front end, or bad ball joints (common on many cars with todays pot-hole free roads everywhere) and when you put the tires out back, the cupping came through as a vibration or hum. This is also a sign of a wheel bearing going bad. Most often you hear it before you feel it.

--Dave.

 

On the road I turn on to go to home from the highway there is a long pothole where the concrete and asphalt meet and it's rough and does jerk the wheel. So wouldn't surprise if there is damage done from that, like I said it just started yesterday when I was coming home from school. I'll let ya know what I find out. Now I need to check the air in that rear tire!

 

have a shop check the ball joints on your truck - they gotta be loaded up to be checked right, so it's best to just have a shop do it - that can cause strange vibrations, but not quite the same as what you're describing.

--Dave.