I have a 1998 F150, 4.6 litre, two wheel drive. When I get up to 60 miles per hour, I feel a vibration, both in the steering wheel and in the seat. Its not an out of balance wheel type of vibration. It doesn't happen at any speed below 60 and fades away as you go above 60.
The U joints were replaced two years ago, could it be that one of them is going again ?
Anybody out there had the same problem, I'd appreciate it very much to hear what the problem was.

 

I would not suspect the U- joints because the vibration you are feeling is in the steering wheel. Check out the bearings at the front wheels. You may have too much play in the axle bearings that is causing the shake . This is a simple check before you spend alot of hard earned cash.

 

Your rear gear oil has broke down - common problem. You'll need 140/90 100% syn gear oil. DON'T forget to add the modifier - book calls for 4 ounces add 6 to yours since you let get this bad.

Do a full Change out of your rear diff oil is what needs to done , use the right stuff and your problem will completey disappear within the next 100 miles.

Seen this problem many times..

Good Luck.


It takes allot to waste these u-joints , my guess is that yours were never bad , just mis-diagnosed . I have 200,00 miles on my joints and there still tight and never been greased.

 

Thank you for your reply.
The rear end fluid in my truck was changed just over a year ago. It's not a limited slip rear end so I don't think the additive would do anything. The fluid level is good and there isn't any whining noise etc coming from the rear end.
If you have any other ideas, I'd be very glad to hear from you .

Thanks again,
Brent W,

 

It not LS - I haven't seen one without , u sure about that? You have an open diff in the back? That would suck..