I have a 98 xlt 4.2, 2wd 5 speed, 140,000 miles and since I pulled uhaul trailer I have a vibration starting at 53 mph and even gets a little loud until 60 the steering wheel and floor even shakes but if I push in clutch it goes away. If I rev with clutch in no vibration, and last but not least it seems to also go away when I back off gas it goes away. HELP !!!

 

U joints Check them out ASAP!

 

I've got a '97 F-150 XLT and it did the same thing in between third and fourth gear, danas transmissions said it was my torque converter. Idk if it is or not, I'm just going to drive the transmission until it dies and I need to get a new one. I'd check out the transmission if I where you.

 

His transmission doesn't have a torque converter - the 5 speed is a manual.

To the OP - if it isn't the u-joints I would suspect the transmission - there's a reason the manual is only rated to tow between 2000 and 3500 pounds, depending on axle ratio. It's a light duty transmission with a known weak input shaft and bearing. Could be a clutch issue too.

 

Don't know if it's the U-joints, but one actually went OUT on my buddy's '99 a few years ago and that was SCARY as hell.

Be careful revving it with the clutch in . . .

 

Was the rear u joint