I have a 93 quad cab 4x4 with a 7.3 turbo .I have been chasing a bucking since i got it . I immediatly thought drive train because when you tried to hold your speed between 1800 and 2000 rpms the truck started to buck like the carrier bearing was bad which as long as the truck is and a free floating transfer case i thought i had it figured out .so I did all new carriers and u joints it wasnt it , it only does it between 1800 and 2000 rpms i have no fuel or air leaks that can be foung by myself or the guys at the local diesel shop . any one ever have this problem ?

 

Check ur front end, almost sounds like a ball joint or possibly a u-joint in front axle ... if its not disenguaged, and if you have auto hubs the only way to determine this is to jack up both sides and spin tires, if one makes the axle turn .. there's your issue

Keep us posted ...

 

front end is sound ,we tore it down and replaced everything up there when i got it ,it had a bit of a wobble when i got it. i replaced eveything even fron u joints while i had it apart .i have lock outs and they were fairly new so those didnt get replaced ,i had a questionable tie rod end so replaced all in the steering as well .it stopped the wobble but the bucking continued .the best way to explain it would be like going from 2nd gear to 5th gear but witha harder lunge to it .it would give you whip lash if you let it

 

automatic transmission ?

 

Its a 5 speed .

 

Sounds like you have something in the fuel system thats not working correctly ..... I honestly would suspect either air or a lack of fuel will be the final case ....

I would get a fuel pressure guage and put it between the IP and the filter housing and monitor the fuel pressure ... I would venture to bet your gonna see some sort of irratic fuel anomily of some sort... if not I would post again .... will come up with something


Might be a long shot but jack up rear end and place on stands...... start engine ( have someone in truck ... just in case ) place in 1st gear and look closley at tires .... from shop floor or reasonably straight surface ... do u notice any tire swell like they could be egg shaped ? ... if possible place all 4 on stands and do the same with the front ..... it could be something there also .... just had this happen with a Charter bus where I work .... was real weird ... would have never thought it would make a feeling such as it did .....

Keep us posted .... will be thinking ......