Since I have owned my truck, I have noticed a vibration above 70 mph, that increases in intensity especially around an (indicated) 75 mph. Sometimes it feels road-induced, as in upon hitting a slight imperfection in the road, the suspension actually componds it and creates the shaking sensation. This activity has lately become worse. I am wondering if it may be due to needing front ball joints (likely lower and upper - both sides) or if it's tire-related. The front tires are newer and have about 80% tread on them, the rears, about 50%.

I noticed just how bad it really is while driving a friend's '95 2wd Cummins automatic for about 100 miles Saturday. It's much much smoother, but he also has about 160k less miles than I do. What are your thoughts, what should I check out, and is there anything you would reccommend that I do. Again, it's not noticeable under 65 or so, but I'm doing more interstate travel now, and with 70 -indicated- being about an actual 65 ph due to speedometer error, it's starting to bother me. Plus, I don't want to compromise safety. Thanks in advance for your thoughts.

 

When was the last time you had your tires computer balanced ? That is what it sounds like to me since it only happens at a good rate of speed.
You may have thrown a weight ... sometimes that happens and people think "I just got it balanced, so that can't be the problem".

Can you track it down front / back / left / right ? I have seen worn out shocks act like this as well.

PISTOL

 

That can be many things.

Check the ball joints, wheel bearings, shocks, alignment, caster, tire-balance, drive-shaft (u-joints and balanced), wheel joints and steering stabilizer (if so equipped). Any of those items can lead to a shimmy / vibration.

sometimes adding a steering stabilizer can help reduce things like death-wobble or shimmy but take note that you're numbing your feel for the road and only covering up a problem, not fixing it.

 

I have been having the same problem with mine. I just had my tires rotated and balanced but the truck still shakes from about 65-75 mph

 

I was having the same problem and finally got it solved.

It was tire related for me. My tires were balanced, but they were out of round (egg shaped). I replaced with new ones and problem solved. Mechanic told me this condition occurs when the tires are not religiously balanced and rotated.

Good luck.