Violent vibration at 63 mph -76mph cannot figure it out

[I support common sense]

When I take my truck out right at 63mph it start to violently shake and it smooths out at 75-77mph. The tires are brand new and we’re balanced, the inner tie rod ends have been replaced and it has not been aligned since, because the wheel bearing were “bad” so I tightened them up and that fixed it. Now there is no play in the bearings at all. I would go back for an alignment but I’ve still got a sagging leaf spring. There is no play in the steering that I can find in the tire, but the steering wheel seems to have some play in the steering rack. In other words I can move the tire and there seems to be no play but when I have someone turning the steering wheel and I follow the moving parts down it seems to have a very small amount of play in the steering rack. But not vice versa. The rpm does not matter so it’s not an engine issue. Anyway, the shake is driving me crazy and I’m banging my head against a wall trying to fix it. Any help would be greatly appreciated.

No tire play at 9 and 3 o’clock or 6 and 12oclock.
1999 ford ranger 390,000 miles.
Edit: my truck is 2wd so the front has regular hubs.

 

[holyford86]

Is the shake mostly in the steering wheel or the whole truck?

 

[pentode]

Just a random idea since I've seen this before - if the bore in the rotor is worn enough to where the outer bearing race (cone) can move even minutely (as in you don't have to punch it out, it just falls out) it can wildly exaggerate any tiny wheel imbalance you may have. The race will go off center and then, depending on how perfectly round your wheels/tires are, you end up with a lopsided wheel. Rare but it's happened to me before and it'll make you pull your hair out.

Edit, just to clarify, this problem is tricky to detect because you don't feel like doing the normal tests. There's no play in the bearings in the sense that you can't rock them back and forth but they can still move laterally. Unusual in a vehicle like the Ranger where the bearings are in the rotor but more common in vehicles with a separate hub - could happen if your rotors are very old and/or ever had a seized bearing.

 

[I support common sense]

Is the shake mostly in the steering wheel or the whole truck?

The whole truck or at least the front.

 

[Bill]

I had that issue and it turned out to be a bad ball joint, but not bad enough to detect from rocking the wheel. The same pattern can occur with poor wheel balance or an out of round tire. Even new tires can have this problem.

 

[Curious Hound]

Seriously; all the above.
Humorously; it's scared to go that fast.

 

[I support common sense]

Seriously; all the above.
Humorously; it's scared to go that fast.

It shudders out of fear.

 

[I support common sense]

Well, I know the steering rack has play in it. When I drive over bumpy terrain I can feel the steering shuddering a little bit. Is that something that could cause it?

 

[Rick W]

Shocks? Shocks are fairly cheap, and most people never change them when they’re supposed to be changed, they wait until they wear out and the truck shakes at 70 miles an hour. A little theory:

The big wobble is probably from something reaching a “resonant vibration level.” No matter how precisely they build the truck or any machine, there are resonant vibrations everywhere, they’re just too tiny to detect. A resonant vibration is when something vibrates, and the frequency it is vibrating at is exactly matched to what is causing it to vibrate, so with each cycle it gets bigger and broader. That’s exactly what the shock absorber is designed to take out of your suspension. If you hit a bump and your tire bounces coincidentally at the resonant frequency, the shock is supposed to dampen that before it builds. BTW, a little bit of play in the steering should not cause giant violent vibrations. “A little play“ might be 1000 of an inch on the wheel bearing race, but it may be a half inch on one of the pivoting arms then again, you could have the lucky situation that a few different things are out that yields that resonant vibration.

Another thing nobody mentioned. On my 97, there is a little cylinder, a little bit bigger than a sharpie, that is mounted on the frame and attached to the steering mechanism under the battery on the driver side. It’s some kind of steering stabilizer/damper. I don’t know if your truck has it, but if it’s worn out, that might have something to do with it.

As always, this is my two cents, a little bit of what I know, and I am not an expert.

@Curious Hound perhaps has the best advice. If your truck has 390,000 miles on it, and the vibration starts at 63 miles an hour, that’s a built-in warning to let you know when you hit 400,000 miles, at 60 miles an hour, everything forward of the transmission is going to blow out into the universe. The reason the vibration dies when you get up about 73 to 77 miles an hour, is because that’s when the 25-ye old aerodynamics of your truck causes the front end to lift completely off the ground which obviously eliminates the rotating vibration.

I have to think of Him, and you have to smile through the rough spots I hope it all helps…

 

[Terrys87]

I see steering and suspension have been mentioned. How about your motor mounts? Usually a thump when accelrating or decelerating but maybe at that rpm is transferring vibrations.

Some front end shops will look at it for free or little cost and let you know what is not right. My last front end alighment shop did the inspection for free when I let them know I was going to have them alighn it.

 

[I support common sense]

I see steering and suspension have been mentioned. How about your motor mounts? Usually a thump when accelrating or decelerating but maybe at that rpm is transferring vibrations.

Some front end shops will look at it for free or little cost and let you know what is not right. My last front end alighment shop did the inspection for free when I let them know I was going to have them alighn it.

I’ll give that a shot. As for the motor mounts, it is a possibility, but the rpm’s do not matter because the shake doesn’t change based on the rpm of the engine. I can put in over drive or out of overdrive at the same speed and the vibration does not change.

as for shocks, how do I test them? I don’t think they have ever been changed, but at the same time suspension isn’t a big deal to me.
@Rick W and @Curious Hound
The engine is in good condition as far as I know, so I don’t think it’s going to blow up, but that is a distinct possibility.

 

[Shran]

Anywhere that there is a bushing, or rod end, or bearing, or is connected to the steering somehow, can be a source of problems like this if there is any wear or slop. If there are multiple worn parts, they will compound the problem.

Slop in the steering rack is where I would start since you mentioned there already is some. A tire out of balance by a little bit can transmit vibration into the rack pretty easily - I know you have had them balanced but I've had tire guys mess that up pretty bad several times on new tires. Could also be a bent wheel! Tire guys & oil change techs are often very low skilled people that don't catch small problems.

Jack up the front of the truck so both tires are off the ground and check for ball joint/A arm bushing wear by grabbing the top & bottom of the tire and seeing if you can wiggle it there. Then drop one side to the ground, wiggle the front & back of the opposite tire to see if you can find any slop in the steering linkage.

Ball joint/A arm bushing wear will show up as slop at the top & bottom
Steering is usually front & back of the tire
Loose wheel bearings will be both.

Shocks would be the last thing I would look at, they won't cause or fix a really bad vibration problem and they can mask other minor problems that need attention.

It can be pretty hard to track these things down sometimes, my beater '88 Ranger has fought me for 10+ years and it still shakes at highway speed. I have gone through the front end completely... new bushings, ball joints, bearings, steering box, column parts, tires, wheels, etc... I just accepted that it is what it is, and now that half of the floor is made of license plates screwed together, I don't much care that it shakes.

 

[fred m]

Mine had a harsh vibration at similar speeds, showed up around 55,000 miles and never got any worse. I checked and replaced everything I could think of. Drove me nuts for years. Finally at about 320,000 miles, I was under the truck one day and noticed play in the tailshaft bushing on the transmission. Replaced that and the slip yoke and it's been smooth as glass since. YMMV.

 

[Cat.diesel.93]

I had one that would do that, and turned out to be the carrier bearing on the split rear drive shaft. Would start about 62-65, and smooth out around 72, just like you are describing. I'd check for play in that too.

The hard part of rotational vibration at speed is...there's a lot that is rotating