Front End Issues @ 45mph or higher

[timgco]

I am running 35" X 18" BFG MT's on my 06 (5200 miles). The tires have around 10,000 on them and have been rotated once on the 04 when I had it. They are wearing fine. (no abnormal wear).

I had them re balanced at the Firestone dealer. They weren't off by much, and than again by the HUMMER dealer and rotated again. They said the tires were almost dead on and the test they did on them said no broken belts. All front end components were tight and the RAncho shocks seemed to be Ok as well. The Fabteck tierods were also check.. again, no issue.

issue #1:
So when you hit 45mph you notice a slight front end shake in the steering column and floor boards. It's the same on both DR SD and PS SD. From 45 mph and higher the shake gets worse. 85mph, the truck shakes badly to the point your hands fall asleep on the steering wheel.

issue 2:
the truck tracks straight when you let go of the wheel below 45mph. When you go above that, the truck wanders back and forth but still tracks straight for the most part. It's like you have to adjust the steering wheel more frequent tahn normal.

So, what so you think? The dealer gets the truck this week.

Ball joint? Ideler arm? Pitman arm? Steering Linkage? Axle?

[timgco]

Thanks for the input.

Tire Balance was the first thing I tried due to the issues. The firestone dealer balanced them abd the HUMMER dealer in Milwaukke rebalanced them and rotated. Same issue. Back to square one.

When the tires were off, I did have freeplay side to side and up and down. Now as to what is normal or allowed variance of what "spec" is, I'm not sure.

the dealer will have to mess with it. I just want to be able to go to them with some ammo and things for them to check so i don't get the standard reply: "Their mud tires, they all do that."

[f5fstop]

Could be:
Marginal lateral runout. If the spec is close to max, a vibration could be felt at speeds.

Bad wheel bearing hub will cause a vibration at higher speeds. (Had this on a vehicle once, at about the same speeds you state.)

Force variation of the tire/wheel assembly. Only way I know to verify this is to have the tire balanced on a load force balancer.

Excessive runout of the prop shaft or pinion flange.

If the tires were rotated and the symtoms remained in the steering wheel, it most likely is not force variation, but....

Does it shake worse if you apply the brakes over 45?

[f5fstop]

Originally Posted by timgco

Thanks for the input.

Tire Balance was the first thing I tried due to the issues. The firestone dealer balanced them abd the HUMMER dealer in Milwaukke rebalanced them and rotated. Same issue. Back to square one.

When the tires were off, I did have freeplay side to side and up and down. Now as to what is normal or allowed variance of what "spec" is, I'm not sure.
check the specs in the service manual DVD I sent you.:
the dealer will have to mess with it. I just want to be able to go to them with some ammo and things for them to check so i don't get the standard reply: "Their mud tires, they all do that."

NM

[HUMTECH]

How wide are the tires, A wider tire can have this effect on A highway which has ruts, the tire being wider than the rut is trying to track in the rut, but will move in and out as the tire does not fit the rut. If it does the same thing on A good(new) flat surface road you definatley have A front end issue, possibly the steering gear may have worn pitman shaft bearing or other issues. Usually when felt in steering wheel can be attributed to A separated tire or bent wheelor a balance issue which will be magnified by A higher than stock offset on the wheel.

[Hummie2]

How is your steering stabilizer?

Here is the description from the shop manual concerning wider wheels and scrub radius increases that can be caused by wider wheels:

Scrub Radius Description

Ideally, the scrub radius is as small as possible. Normally, the SAI angle and the centerline of the tire and the wheel intersect below the road surface, causing a positive scrub radius. With struts, the SAI angle is much larger than the long arm/short arm type of suspension. This allows the SAI angle to intersect the camber angle above the road surface, forming a negative scrub radius. The smaller the scrub radius, the better the directional stability. Installing aftermarket wheels that have additional offset will dramatically increase the scrub radius. The newly installed wheels may cause the centerline of the tires to move further away from the spindle. This will increase the scrub radius.
A large amount of scrub radius can cause severe shimmy after hitting a bump. Four-wheel drive vehicles with large tires use a steering damper to compensate for an increased scrub radius. Scrub radius is not directly measurable by the conventional methods. Scrub radius is projected geometrically by engineers during the design phase of the suspension.

[mikejr]

me thinks its a bad kanooter valve assembly.....

[Hummie2]

Tim...

It could also be possible that its not a steering problem. It could be driveline related. How are the rubber bushings that mount the front axle assy. to the frame/crossmembers? I believe you said before that you first noticed it when you came back from Moab, is it possible one of the axle rubber isolaters could have been damaged? Also check your control arms on the rear axle. I recently changed my rear ride height slightly and could feel a vibration in the front floor and steering wheel. I had to install a CV rear driveshaft to cure the vibration. Those driveline angles are only correct when the "D" height is within spec. If it is driveline related the vibration will kill a set of pinion bearings in a short time.
Bad bushings in the rear control arms will not only alter the driveline angles, but will make the truck road wander especially on accel/decell.

[timgco]

Dealer called with the standard reply. They're mud tires, they are gonna do that.

[HUMTECH]

Also try and find A tire shop that can road force balance the tires. Any wheel sizes 18" or larger we always recommend this. With A road force balance the tire and wheel get matched and then weight is added to balance the assembly.

[timgco]

Originally Posted by HUMTECH

Also try and find A tire shop that can road force balance the tires. Any wheel sizes 18" or larger we always recommend this. With A road force balance the tire and wheel get matched and then weight is added to balance the assembly.

Road force test was done twice now. And was good!

The issues just started doing this a week ago. The dealer is going to throw a set of stockers on there and see what happens.

[timgco]

Dealer let me down! Said tires are the issue. They did not even put stock tires and rims on to rule out my tires were the issue.

I miss the old Service manager.