I have a 97 F-350 4x4 with a lift and big tires. 315/75R16 to be exact. lifted 4-6". I bought it a couple of weeks ago and it was already this way. It drives smooth until about 60+ mph, if I hard accelerate, sometimes it seems to appear after i let off the accelerator. It shakes the whole truck and doesn't seem to be in the steering wheel as much as it is in the body of the truck. And it seems to be worse in the front of the truck than the rear. I will be going in cruise control about 70 mph on flat, dry asphault, the vibration will get very bad then seems to taper off almost non-existant, then return again. There is no vibration at a standstill or under 50mph. I had a NTB store balance and rotate the tires before we left the town it was purchased in. The tie rod ends could be changed, I felt unsure on the angle of the rear drive shaft so I shimmed it down trying to alleviate the vibration as much as I could. I also rotated the driveline slip 180 degrees to check for unbalanced drive shaft. I changed the carrier bearing mount, cause it was gone, that helped but didn't fix it. The bearing itself felt and sounded good to me. The u-joints are good. There is just a very small amount of slack on the front hubs. I lifted it off of the ground, grabbed the top and bottom of the tire and tried to wabble it up and down and felt very little, but some is there. We would love to take it to the beach next week, but I dont want it rattling us all the way there. Does anyone have any knowledge, or experience in this particular problem. Any advice would be appreciated. Thank you in advance.

 

ok, I've rotated the tires and put the two new ones on the front and the worn ones on the rear. They have uneven wear and wanted them in the rear. I replaced the drag link bar, and replaced the driver side inner and outer bearing in the hub (took it to a shop for that one). There still seems to be a vibration only less in severity and maybe more to the rear instead of concentrated in the front. I really think it is mostly tire right now.

 

Classic unbalanced tires. when two (or more) slightly unbalanced tires synchronize, the vibration gets worse... so it seems to come and go... usually at certain speeds because of the natural harmonic resonance frequency of all solid objects. (in this case, all or part of your truck.)

Bigger tires are harder to balance and most tire shops think that close is good enough.
Almost no shops will do it properly because it is too time consuming. The proper way is to mount a tire and check the balance. if it is too far off it can be dismounted and rotated on the wheel until the best position is found, or at least a reasonable one.

if they are very far out most shops will do one of two things, add weights further and further from where they are needed because there is no more room, then quitting and calling it good enough or they turn the balancer from dynamic balance to static balance which is easier to do and works great unless you actually drive your vehicle.

Take them to a shop and tell them you want them zeroed out, and are willing to pay extra to have this done. If they can't or won't, bring them to someone who can and will.

 

im going through san antonio on thursday, ill take it to discount tire and see if they will do it. I appreciate the response. Thank you