[twiztid1981]

so heres the deal when i acelerate slow or fast at 40-45 there is this vibration, if im drivin in a 40 speed zone it stays constent if i gun it its a quick vibration, the only time i dont feel it is when my methonal is on, infact the shifts are very smooth, but dont get it twisted it was doin this well before i put that kit on, my truck has been doin this since i got it, it only has 44,000 miles on it an another thing, since like two days ago its been feelin werid as it shifts its kinda likke the rear end is felxin as it shifts it just feels like the axel is movin up then down, its not constant but it just feels werid, an to clarify i have no lift i have stock tires on it, an i have checked the obviouse stuff my drive line seems fine theres no excesive play im not seein anything leakin down there, any help would be apreciated

 

[sevenmalards]

so heres the deal when i acelerate slow or fast at 40-45 there is this vibration, if im drivin in a 40 speed zone it stays constent if i gun it its a quick vibration, the only time i dont feel it is when my methonal is on, infact the shifts are very smooth, but dont get it twisted it was doin this well before i put that kit on, my truck has been doin this since i got it, it only has 44,000 miles on it an another thing, since like two days ago its been feelin werid as it shifts its kinda likke the rear end is felxin as it shifts it just feels like the axel is movin up then down, its not constant but it just feels werid, an to clarify i have no lift i have stock tires on it, an i have checked the obviouse stuff my drive line seems fine theres no excesive play im not seein anything leakin down there, any help would be apreciated

If you have a two piece driveline I would point at the carrier bearing.
If not then :dunno:

 

[twiztid1981]

i checked that, it seemed to be in good shape

 

[bismic]

This may or may not apply:

Vibration/Hop at 40-48 MPH, Trucks with Trailer Hitch:
Some 2005-07 F-Super Duty trucks with long wheel base (over 156") may exhibit what is described as a hop on smooth or coarse road surfaces. Although Ford considers this to be characteristic of trucks with a GVW of over 8500 pounds, some drivers may be more sensitive to the condition. There is a damper kit (P/N 5C3Z-5D008-A) available to correct the hop under the described conditions. It will not correct shimmy, harsh ride or vibration after hitting bumps. TSB #07-5-11.

 

[bismic]

Here is another:

F350 DANA 80 Dually Rear Axle Chatter on Turns:
Ford now recommends using 75W-90 gear lubricant along with 8 ounces of friction modifier to correct and prevent a chatter condition on turns. If chatter is slight, this can be a normal operating condition. If chatter is still severe after replacing the fluid, disassemble the differential assembly and replace the clutch pack, P/N 3C3Z-4880-AA. Prelube the clutch friction plates with friction modifier before assembly.
TSB #04-16-04

 

[bismic]

Probably not this, but here is a third:

2003-05 Various Running Problems, Check Engine Light; New EBP Sensor:
Trucks built before 1-17-05 that exhibit buck/jerk, hesitation, lack of power, stalling, stumble, black smoke, surging, rolling idle, changes in engine sound at idle or when driving at a steady speed, or with the trouble codes P2263 or P0299, may have an exhaust backpressure sensor signal that is incorrect or erratic. A revised EBP sensor is available if this is found to be the case. Part number 4C3Z-9J460-A. Broadcast Message 3815.
Normal EBP signal reading should reflect atmospheric pressure with the key on/ engine off. Typically, this is 14.7 PSI/0.88-0.9 volts at sea level, decreasing one PSI/0.10 volt for every 2000 feet of elevation. It should be within 0.5 PSI of BARO and MAP sensor pressure signals.

 

[bismic]

Last one:

99-07 Super Duty F-Series Two-Piece Driveshaft Shudder:
Some trucks may exhibit a vibration on moderate to heavy acceleration from a stop. This is usually due to too high of an angle through the center u-joint. The correct angle through the u-joint should be 0.5-3.0 degrees (compare front shaft angle to rear shaft). Check the engineering number of the center bearing bracket to ensure it is the correct application, and replace if necessary. If the bracket is correct, the shudder may be corrected by shimming the bearing down from the bracket using up to three 1/4" shims, part number E0TZ-4A209-A and two grade eight bolts long enough to expose three threads above the nut when tightened to 46 ft/lbs. Loctite is recommended. Broadcast Message 0518, 1475; TSB 04-22-7, 05-17-6, 06-23-4.

 

[twiztid1981]

just wana say thanks for the help, i broke down an bought new tires, the ones i had wernt bad but they wearnt great well needless to say it dosent do the vibration any more at40-45 soooo kool beans