1998 Expedition 4x4 heavy vibration during acceleration

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Jun 6, 2012 | 08:37 PM

Bsteveo1985

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1998 Expedition 4x4 heavy vibration during acceleration

1998 expedition has heavy vibration between 40 and 70 mph during acceleration. As soon as I let go of the throttle, the vibration goes away which leads me to believe it is the driveshaft. I have checked the u-joints and they all appear to be fine, no play. I pushed up on the driveshaft where it comes out of the transfer case and it it probably moved about 3/8 of an inch. I have not removed the driveshaft to inspect. Does anyone have experience with these types of failures. Could the splines on the driveshaft be worn, or is it something internal in the transfer case. The output seal is also leaking a bit where the driveshaft comes out of the transfer case.

1998 Expedtion XLT
4.6L 4X4
135,XXX Miles

Thanks for the responses.

Jun 7, 2012 | 11:30 AM

alloro

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Quote:

Originally Posted by Bsteveo1985

1998 expedition has heavy vibration between 40 and 70 mph during acceleration. As soon as I let go of the throttle, the vibration goes away which leads me to believe it is the driveshaft.

Nope, if it were the driveshaft the vibration would be there all the time. What you're experiencing is a misfire due to a bad plug, COP, or injector.