hlhunt08

1998 4.6L 4wd: When I hit about 35mph upon accelerating, the truck starts vibrating moderately (seems to be drive train related) the vibration continues whenever I accelerate. Stops when I cruise or decelerate or drop below 35

FYI: I have in the last year or two changed the rear axle seals
I do have a transmission leak (about one qt every 600-700 miles)
if that's pertinent.

loudmustang

One item to check are the ujoints. You can get under the truck and try to twist the drive shaft by hand and see if there is any play. Mine had no play but squeeked and vibrated also, changed them and solved both issues

Insaneba

U joints and tranny ount are two good areas to start with. After that, check rear diff fluid out.

hlhunt08

Thanks for your advice, I will check these out as soon as it dries out and warms up a bit. (hope it makes it that long)

alol24

Well guys my 2011 F150 Lariat with 5.0 had the same vibrating issue on take-off. I called Ford directly and the problem found at the dealership was in the rear-end, apparently there were several metal shavings found inside that came from the spider gear. The gear was replaced and it solved the problem. Has anyone had problems with self acceleration on the F150? Mine did that about 2 weeks ago on take-off, I was in a 40 mph zone and it accelerated to 70 mph before I stomped my gas peddle 3 times. I had 3 people in my truck and they all saw that I did not have my foot on the gas peddle.

MCpllabelle

Had the same issue then replaced U-Joint. The problem went away. Truck now runs smooth at highway speeds. Give that a shot.

jaycarl

Never heard of this "self acceleration" in a F150. If the pedal was sticking it would stay at 40mph, it wouldn't accelerate by itself.

I would get that fixed ASAP before someone gets hurt or worse.

MCpllabelle

Fully agree!! Get that fixed up brahh!