Just wondering if someone could help me out here?
I got a 1999 F150 with a 4.6V8.
I am getting a strange shaking when I take my foot off the gas pedal, and start to decelerate.
It is slightly noticable at higher speeds, but more prominant when I let off the gas??
I had the tires checked, they are fine. The drive shaft is tight, so anyone else have any ideas?
Thanks.
Jay

 

If it's happening after 40 mph - You probably need to change your rear gear oil. It will keep getting worse as times goes on.

The friction modifier breaks down - It will eventually start to shake the whole truck when it gets bad enough.

Specially with 9.75 rear gears.

 

Thanks a million.
I will try that this weekend coming up.
I see you need to use 75W- 140?
Good thing I would of thought 80W 90 would of been good.
Thanks again.

 

BUDDY YOU HAVE EXACTLY WHAT JUST HAPPENED TO ME ABOUT A MONTH AGO it would just start shaking out of the middle of noware... and it was so bad it would shake it out of gear!!! i took my dad for a ride in it... and he is the mechanicle type and it totally stumped him... got out after it happened and no smells or nothing... so i dint drive it for about a month till i could find time to get it in and get it checked out... took it in and the mechanic took it for a test drive... it shook and he dint know what it was. we got back to the lot and we got out and all you could smell was brakes burning. i said y is that becasue the brakes were off the hole time... i mean not applied at all. he took the wheel off and looked at it...

COME TO FIND OUT IT WAS MY PARKING BRAKE THAT WAS LOCKED UP!!! it was rusted closed. i dont know y... but one day it was ice cold out... and i went to take the brake off and nothing happened... then i put it in reverse and nothin happened then i reved it up and dropped the clutch so i could get it to move... and there was a big SNAP!!! and then i was off.... and it never worked after that. anyway... i hope i helped you out!!!


let me know what the problem was k?!?!?!

im almost positive this is your problem!!!! if u use the parking brake i am sure it is the problem!!!!!

 

Not the parking brake thats for sure.
I took it off to look, and I need brakes and drums bad.

 

parking brakes are very deceiving. bigjay urs could be dragging very lightly, and we all know heat makes things expand.

 

I changed the rear drums and shoes. I went with the semi metallics.
It is weird, case I still get a weird hopping when I apply the brakes. I adjusted them so they are nice and snug, and then backed them off a bit.
When I am driving forward at a higher speed, and apply the brakes you can see in the rearview mirror the back hopping a bit. Not so much that someone behind could see, just enought to make it noticable in the mirror.
Oh and now my rear ABS works too.....yeah!

 

that sounds like my truck, or atleast very similar. mine bounces at 45-50 and the bed is barely noticeable in the mirrors. i still swear up and down the cause is from the front end. i've had numerous causes and fix's, bad alignment being one of the first ones, down to a loose idler arm. i believe any play in the front end AT ALL on these trucks causes a bounce