I have a "wobble" for lack of a better term at my front drivers side tire, i've rode shotgun while a friend drove and it's apparent it's coming from the drivers side, just like clock work the wobble starts at 35mph and is gone by 40mph, it doesn't matter if i'm accelerating or decelerating (it wobbles from 40mph to 35mph too), i can power through it while accelerating and you wouldn't even know it existed but under deceleration it's very pronounced, i wouldn't describe it as a shimmy or shake, it doesn't vibrate through the steering wheel, the truck tracks straight and true, the best i can describe it is my tire feels as though it becomes oval (egg like) between 35mph and 40mph, the rims are stock 16x6, tires are 4yrs old (16k miles), 235/85/16 BFG's, the front driver side tire only took .75oz weight when it was balanced and it's still intact, the tire has no obvious sidewall or tread bulge, the tread is wearing evenly with no signs of anything irregular, the front-end is tight with the exception of passenger side tie rod (about 1/16" of play) the truck does need new front shocks though, i have yet to rotate the rear tires up front to see if the problem still persists, i wanted to see if anyone has any ideas, suggestions or comments before i do so, thanks.

 

Have you rebalanced the tire recently? If not start there.

 

Not yet, if all else fails i'll have them rebalanced, when i've had tires out of balance in the past they generally weren't noticable until around 50-60mph and it was more of a "vibration" that you could feel through the steering wheel that didn't go away at higher speeds, this is more speed sensitive, it only happens between 35 an 40mph.

 

I would put the back tires on the front quick. That way you can eliminate a tire issue right away.
If i had to guess i'd say maybe outta balance, mud/debris on inside of rim, maybe lost a wheel weight.

As a side note, I had a vibration I was absolutely certain was in my drivers side. Turned out to be on pass side. Of course that was a 94 2wd though.

cheers and best of luck.

 

I worked at les schwab for a while and sounds like you have an out of round tire. BFG's arent the greatest tire and are known to go out of round. It will balance fine because its the tire moving up and down on the road. Switch it to the other side or the back and see if the problem persists. As noted before i would check for mud or what not on the wheel and see if the wheel is bent. A balancer will pick it up if its a bent wheel. After that theres nothing to do besides replace the tire.

 

If the tire was out of round it should come have been caught when they balanced it. And even if it is out of round it should be noticable under 35 mph as well, he states that it only happens right on or around 35 mph.

 

I neglected to mention in my original post this issue has existed for the better part of a year (i know i should have addressed this problem back then) but life has a tendency of getting in the way sometimes.

It's the 5mph window that has me baffled, this problem only occurs between 35 and 40mph, i'll rotate my tires and see what happens, i've been told a bad shock can cause similar symptoms but why only between 35 and 40??? i need new shocks anyway so at the very least it's an excuse to work on the truck.

 

Again, have it balanaced-that is cheap. Then try rotating it to make sure its the tire. Put a spare in it's place, see if it continues. If it does, your driveshaft may be out of balance.

 

I would start with the simple stuff first,unfortunately vibrations sometimes may only be diagnosed by changing parts till you get it.I would start with the simple cheap stuff.First,I have had bad shocks cause this exact problem,vibration at a particular speed,remember that the whole vehicle is vibrating and the vibration may resonate more at a particular speed due to a number of factors coming together(I know what I want to say but I'm having difficulty putting it into words,the science of metal vibration and amplification was explored and successfully tested my a guy named Nikola Tesla,I am driving at kind of the same thing)but usually on a vehicle with the IFS you will see cupping on the tires,you have a monobeam so you may not see the cupping.Next,I would check all front end components for play and do an alignment.This is cheap and you don't have to shell out any cash yet(if you don't know how to set the toe on your truck let me know and I can show you how to with some spray paint and a tape measure).Next I would check the wheel balance,and while you're at it check the weights on your drums make sure none of them are missing.I had this problem once on a KW.It turned out that when they did steer axle springs they had put one wedge one way and the other wedge the other way.Next I would check your drivshafts to make sure they are in phase and the weights are there also don't forget to check the u-joints for excessive play.If these things don't work and everything checks out then we'll have to go from there.Like I said earlier vibrations can be extremely difficult to diagnose and sometimes it just comes down to trial and error.

 

Well i rotated the rear tires to the front today, a big PIA but i needed to eliminate the tire/wheel/balance as possible causes, took it out on a test drive and the 35-40mph wobble still persist so i can pretty much rule out the tire/wheel/balance as the culprit, so i picked up a set of KYB's and time permitting will either install them today or tomorrow and see what happens.

 

why not replace that tie rod with the "1/16" of play", could be the issue and needs to be replaced anyway
loose connections can cause strange things to happen, like wobble @ 35-45 only

 

This problem could possible be a worn bushing in whats called the tracking bar it mounts to the frame on the drivers side and comes down to the frt differntial the bushing on the frame mount can become deteriated from P/s fliud leaking on it I had a similar problem on my 1977 ford when I went to change that bushing it was extreamly difficult to install even with a press maybee theres an aftermarket neaprime or solid plastic bushing the factory stlye is metal backed rubber I attempted to install this style it almost needed to be compressed before pressing it in so that why i would recomend trying a plastic bushing and it would be better for oil resistance

 

In readed through discription again I am not positive the 3/4 style uses a track bar the thing to check is sidetoside movement of the frt differentail on my rig it only picked up the vibration when you hit a bump but only at the speeds you describe

 

Put the new shocks on this evening and took the truck out for a drive, the wobble is far less pronounced, almost non-exsistent, still feels as though i can sense a very slight wobble but i may just be looking for it too hard (friend says he doesn't sense anything) but i'm happy with the improvement for the time being, still not sure why a bad shock would cause an issue at only 35-40mph but stranger things are possible.
Thanks for all the replies

 

The old shocks that you had amplified the "resonant frequency" and the new shocks fixed it.Do a little reading on Nikola Tesla and search resonance.He did many experiments with this kind of stuff,very brilliant guy,but also a lotta nutty.Thats what I was driving at in my previous post.