This problem just came up the other day when I was driving my truck and from around 35-50 mph whenever you push in the pedal at 20% to 30% throttle you feel some part move and then when you let off the pedal you feel it move back. Also going down the road there is a slight drone noise and vibration, going down a hill with the cruise on is when you really notice the vibration. The part moving back and forth sounds like its coming from the transmission, drive shaft, or axle. Any one have any clue on what this might be?

1) Drive shaft look fine (U Joints, and carrier bearing look fine also)
2) Axle looks fine
3) Transmission brackets look fine
4) No leaks on any components (EX: Transmission, Axle...)

Whats currently done to the truck:
2008 Ford F-250 Powerstroke
DPF Delete
H&S Tuner (On stock 65% of the time)


Any help is appreciated!

 

Update: Sounds like its coming from transmission/transfer case area. Vibrations seems to be coming from the steering wheel and floor next to transmission/transfer case.

 

Is the transfer case accidently engaged? You might need to crawl under and watch the arm as someone switches from 2ho to 4hi and back. Being engaged on dry pavement could easily lead to slow speed walking or high speed vibration on acceleration/decel.

 

I had this problem once...the exact symptom at the exact speed.

the root cause was a broken rocker......huh you say..how would this cuase tranny problems????. well the torque converter locks in the 35 to 45 MPH range....when this happens theres no buffer between engine and tranny. the broken rocker was an intake rocker...this cuase a piston suction that pulled back on the drive train...causing the noises and vibrations. once I replaced my rockers, the drive tran problem stopped.

moral of the story....a problem at the left rear of the truck can be caused by something at the right front of the vehicle....don't limit your analysis to a small area.

 

How do I know if it is a broken rocker, without taking the valve cover off. They are a little hard to get to.

 

regens alot
smokey emissions
poor mpg

 

Not to mention a thumping sound in the intake and excessive valvetrain noise.

 

I have none of these issues currently pulled the air intake and started the truck up and no thumping,
I have an aftermarket exahust with dpf delete and there's no smoking, and I'm getting 22 highway mpg.