1987 Chevy r10 front end vibration at highway speed

[LB2387]

I have a 1987 350 chevy r10 that has really bad vibration in the steering wheel at around 65-75mph. I just replaced the tires last week thinking this would solve the problem and i needed new tires anyway. New tires did not make any difference. I have replaced all 4 shocks within the last 3 months. I have checked the tie rod ends and the ball joints and there is no play in either of them. I had the alignment done maybe 8-9 months ago. Im kind of stumped on what to check next. Any help would be appreciated

 

[bucket]

Assuming the new tires were balanced too, correct?

Bent wheel? It's very rare, but I've seen heavy-sided rotors before.

 

[LB2387]

Yeah new tires were balanced. Not sure about a bent wheel. Ive had the truck for about 10 years and its never been an issue. How would I check to see if the wheel is bent? Would it have to be visibly bent, or could just a little bit throw it off?

 

[bucket]

You can just jack it up and spin the wheel to check it. It should be noticeably out of round to cause a good shake.

Did the shake develop over time or start all of the sudden?

 

[scottybaccus]

loose tie-rod ends will allow a wobble in the steering, especially with minimum toe-in. You can check that by grabbing one wheel and turning it by hand, watching for slop in the linkage, and delay in the opposite tire following.
loose ball joints contribute to this.
Insufficient toe-in will contribute.

 

[MrMarty51]

Tr4y installing the rear tires on the front, see if it still shakes then.
Insufficient toe in will cause some real bad road wandering.

 

[LB2387]

It kind of developed over time. It shakes really bad around 70 mph most of the time, but every once in a while it will ride ok at those speeds, but it is rare. I dont think its an alignment issue because i can let go of the steering wheel and it will drive straight as an arrow. Jacked up the front end and Tie rods and ball joints all checked out good. There was a little bit of play in the wheel bearings but not much, probably less than 1/16". I spun the front tires and the wheels look straight as far as i can tell. It acts like a wheel is out of balance but I was having the issue before i had the tires replaced; and it acts the same after replacing them

 

[350runner]

Tire rods and alignment they can look ok but once the weight of the vehicle things are totally different.

Sent from the dust in front of you!

 

[MadOgre]

What about A arm bushings?

 

[LB2387]

Upper control bushings have been replaced. The lower bushings look kind of worn out. tryed to move control arm with a pry bar and it didnt look like it had any play in the bushings, but I guess the vehicle weight may have a differernt effect

 

[scottybaccus]

Jack up a wheel and try to wobble it side to side, and up and down. Any play will be in the tie-rods, or ball joints, respectively.

 

[LB2387]

I did that Scotty, Everything is tight as can be. No play at all in tie rods or ball joints. I was wondering if it was the control arm bushings, shouldnt it cause issues at all speeds? not just the 65-75mph range?

 

[chengny]

Sounds as if you have carefully gone over everything on the output side of the steering system, but how about the input side?

Steering gear securely mounted to the frame?

No cracked frame issues?

Excessive internal play in the steering gear?

Pitman arm tight on steering gear output shaft?

Rag joint tight?

The fact that the shake hits suddenly at high speed (rather than building gradually as speed increases) - and also that the truck runs straight and true - suggests that the movable components are tight and doing their job. Maybe too well.

It's possible that under smooth operating conditions, and assuming the dynamic section of the system has little or no play, there will be no apparent vibration felt in the steering.

But consider what happens if a major stationary component - or one that sees only limited movement - is worn (or not securely mounted).

When there is a sudden disturbance imparted to the output side (due to bumpy road conditions, quick direction changes, uneven braking, etc) and the linkage on that end is very tight, that shock is transferred back to the input side.

Since nothing is loose enough to dampen the vibration in the dynamic end, the force will continue back up the steering system. It will not be dissipated until it finds a component with sufficient "give" to absorb the road induced shock.

If, for example, that spot happens to be the steering gear (because of loose fasteners/cracked frame, etc) you will feel it come through the steering wheel. And it will feel exactly like a front end problem.


Anyway, having said all that, I would certainly snug up on your wheel bearings. When you say you observe about 1/16" of play - you don't mean end play do you? If so, that is too much - I think.

 

[LB2387]

Chengny, it does feel like the steering column has a little bit of play in it. I know that there are some small torx bolts inside the steering column that are known for backing out in these models. Ive been meaning to fix it but I havent gotten around to it. Ill do it this weekend and let you know what happens. I also repacked the front wheel bearings and that tightened them up, but didnt make any difference in the ride quality.

 

[chengny]

Is there anything you control that can stop the vibration?

For example, does the vibration immediately cease if you let off the accelerator? How about if you let off the gas and shift into neutral? Or does wiggling the steering system back and forth a bit ever settle it out?

As opposed to making it stop, is there anything you control that can initiate the vibration?

It shakes really bad around 70 mph most of the time, but every once in a while it will ride ok at those speeds, but it is rare.

On those rare occasions when you can bring it up to 70 MPH - without the vibration - is it possible for you to intentionally cause it to start shaking?

By that I mean, is there anything that you can do (e.g. turning the wheel slightly, tapping the brakes, hitting a bump in the road, etc) that seems to consistently bring on the shake.

I know you are convinced this is a steering system/front suspension problem, but have you inspected the drive train and engine/transmission mountings for any worn or loose components?