loud thump when accelerating =[

[fordkid417]

hello, i have a 1998 ford explorer, 4.0L, 4WD. fourdoor.

when i accelerate there is a very loud thumping noise coming from what sounds like the front driveshaft. it also happens when i let off the gas. it makes the noise when im in 2wd, and even worse when im in 4WD.

i can turn the front driveshaft 1/4 turn when the truck is turned off in park. is this normal? any input on what i should do?

thanks in advance for anyone that can help, this is my only way to school and my motocross races.

 

[my98nnj]

Check the motor mounts.

 

[fordkid417]

i put it on my friends lift and checked all the motor mounts, everything was fine on that. it used to only make the noise until i reached 35mph, and then it would stop completley until i turned the truck off. now it does it all the time

 

[bretb]

Just curious if you've checked the u-joints, and wonder if by chance you have a front axle shaft going out. I've heard of u-joints making a "thud" when putting transmission in gear, and when you release the brake pedal at acceleration. Hope you find out what it is.

Bret

 

[RickOTR]

Sounds like U-joints to me too. When was the last time you greased the driveshafts slip-yoke? the thump/cluck noise you are hearing is the driveline catching up with the rest of the drivetrain or transmission when you accelerate/decelerate. A 1/4 turn in the driveshaft either way is normal.

 

[rloftis]

You may also want to check the Transmission mount. I discover on my 99 that one of the nuts holding it to the cross member was missing and another was very loose. I put new nuts on and torqued down and no more clunk.

Hope this helps!!!

 

[fordkid417]

thanks everyone for helping me out, this sunday im going to try everything you suggested, hopefully something will work.

 

[marknz]

Hi I posted yesterday. Same sort of thing with my 2001 explorer. Ive got a thumping but only in 4WD Auto. If i push 4WD High is stops immediately. If I push auto again it starts straight away. It is like a thumping at any speed. I can be accelarating, coasting, braking. It can continue if I put it into neutral while driving.

Can anyone please give me an idea what it could be.

Cheers
Mark Auckland New Zealand