vibration

I would be looking for metal to metal contact , loose trim, stack mount bushings , loose visor .

 

Tires do cause vibrations that come and go. This is because as you turn corners and the outer tires turns faster than the inner ones and they all end up indexed a little differently all the time side to side and front drive to rear drive. Some vibrations get canceled out from the tire on the other side, or shock absorbers. The cancellation is limited and random due to the change in speed and load and road surface. Some tires are out of round or develop a high spot that actually bounce the axle down the road. This can develop it's own pattern or be very random as well. As fas as trying to diagnose what is the cause there are things you can do to help pin point. Any tire shake normally shows up around 55 mph. The frequency of tire rotation compared to any other drive line component is the lowest. At 55 mph, if you can almost keep up with the vibration by counting really fast, then it is a tire. Everything else just spins too fast and you can only feel the vibration. Tires cause more of a "shake". Vibrations from a bad ujoint or working angles are more of a "buzz". Anyway, here are some things you can do... Get to the speed where the vibration/shake is the worst. Hold the clutch in and go to neutral. This takes all the load off the drive shaft. If the shake is still there, I would say the driveline is ok. Also, if you clutch, let the engine go to idle, but keep it in gear then the input shaft is still spinning faster than the flywheel so the pilot bearing is spinning too. If your shake or vibration changes then it would be something with the clutch/pilot bearing, trans area. If you shift or split gears at the speed the shake is the worst and maintain that same speed but in a different gear and engine rpm and the shake is the same, again the trans/driveline is ok and you are looking at a tire. You can also dump your suspension at that speed and if your axles have enough travel you will feel the higher frequency vibration normally associated with a bad u joint or ride height levels.
Hope this helps, good luck!

 

Did this problem come about gradually, or did you first notice the vibration after any driveline work? (tire replacement, R & R a u-joint, brake job, etc.), if so odds are something in that area is the cause. I am headed to the tire shop this a/m for drive tires, and to (hopefully) correct a problem caused by recently installing two new steer tires, along with new centramatics. My hub piloted wheels are "wallowed" out. Installing the wheels without using the Tru-Balance wheel centering gizmos will cause them to be slightly off center, and cause an "out of round" type of ride (aka vibration). This problem happens pretty often in older hub piloted equipment that has been removed, and re-installed often. I was aware of this problem with my drive wheels, and should have used the gizmos when remounting the steer wheels, but it slipped my mind. Wheels are of 2001 vintage, I did a tire and wheel swap during the trade-in / purchase of my present truck, a 2004. Not anticapating any problems with the newer unit, I guess I decided to hold on to one of my older pita problems.
Good Luck!

 

We are seeing more and more that the wheel will not automatically be centered on the hub because of excessive gap between the centering tab of the hub and inner diameter of the wheel. Like you mentioned, it is causing out of round. You cannot balance this with anything, this tire is physically mounted incorrectly. The tire needs to be centered as perfect as possible. This happens with drive tires too. Anytime a tire is removed for rotation or a brake job it is possible this can happen. What I do is use a spin balancer machine to spin up the wheel while on the hub. As the tire is turning relatively fast you will be able to see it going up and down if it is out of round. I will take my tire crayon and hold it just so the high spot makes contact. I will stop the tire and find my mark the crayon made. This mark will locate the high spot. Turn the tire so the mark is at the top. Loosen the wheel nuts and give the tire a wiggle to let it settle and re tighten the nuts. Sometimes it might take a try or two to get it close. Just remember to retorque your wheel nuts when you are done. To be honest this cures more tire related shakes than re balancing does.

 

I have had u-joints fit lose in a half round yoke (the ones with the straps) and wares out the yoke where the u-joint caps fit and it slides back and forth. Replace yoke and joint fix my vibration.

 

if its driveline vibration i would check your driveshaft to make sure it is phase. u joints aligned with each other. if not you can get some driveline vibration

could also be tire balance. if you guys balance your wheels with lead weights. the more the tire wears the more the balance changes so if it lead you need someone to constantly change the weight on the wheel. we use that equal stuff in our tires.

 

I have a 92 379 Pete daycab with the standard airlief and around 55 to 60 I get a vibration that is so violent that sometimes feels like the whole truck is bouncing down the road. I can push the clutch in and still have no affect in change. I have replaced wheel barrings in the front end, king pins, all bushings in suspension front and rear are new. All u joints new, checked drive lines as well. Brand new tires. (Problem was occurring with old tires also) new cab bushings, nothing has helped please help me its so bad I can't even keep coffee in my cup as it will knock it out of the cup holder.

 

Shocks replaced?

 

Dustin C, I've got a 94 379 daycab with the EXACT same symptom. It will shake my coffee right out of the cupholder, i get so p!ssed i almost laugh. I have done every repair you have except the rear suspension bushing, i've also put new front springs and shackles. I swear some of the rims are square or something. It had the same bounce with cheap chinese ling-long tires and i just put 8 new bfg dr444's and they shake just as bad.