1997 Ford F-150 Truck shakes at 35mph or above

PDDF150

MEMBER
1997 FORD F-150
V8
2WD
AUTOMATIC
138,700 MILES

I just bought this truck used from the original owner, who seemed to use it seasonally. About a week after driving the truck it started a shake. It will shake notoriously between 35-45 mph and above. Also, it will shake when I have to slow down quickly. My only thoughts are could it be a torque converter/inhibitor, or the rear end? Also, how do I determine which rear end is in the truck, because it is sucking gas (about 11mpg).
Thank you very much for the help in advance.

3 Replies

JACOBANDNICKOLAS

MECHANIC
109,755 POSTS

Actualluy, if you have a 4.6 or the 5.4L, that is about average mileage. As far as the vibration, have you checked u-joints?

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Sunday, July 18th, 2010 AT 10:30 PM

PDDF150

MEMBER
1 POST

I have not checked the U-joints. How do I do that?
Also, there is a slow leak (few drops per day) from the rear end yolk seal. What are the consequences of this?

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Monday, July 19th, 2010 AT 11:53 AM

JACOBANDNICKOLAS

MECHANIC
109,755 POSTS

The slight leak isn't uncommon. Just make sure to check the differential fluid and keep it full. If it is only a couple drops per day, it will go down slowly, but keep an eye on it.

As far as checking the U-joints, park the truck, place the parking brake on, and place the transmission in neutral. Make sure the vehicle can't move because you need to get under it. Craw under the truck and check at each end of the drive shaft to locate the u-joints. Once located by hand wiggle the drive shaft back and forth / up and down to see if there is any play from the joint.

Let me know what you find, and make sure the truck can't move when you are under it.

Joe

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Tuesday, July 20th, 2010 AT 12:25 AM