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Idler (and Pitman) Arms:

I was having my alignment checked after a long week of running dirt roads and mud holes and the like and was told that the idler arm needs to be replaced. The owner of the shop suggested that we replace the parts prior to alignment. To those of you who have up graded your steering components (I have a 95 wagon) have you noticed much difference with the hd parts? As I recollect the hd and standard parts can not be mixed. Since I probably answered my own question and will install the hd parts does anyone have part #'s and are they available as a complete kit?

The idler arms are a constant problem on the Hummers. When I had a 95 truck I replaced the idler and pitman around 16,000 miles. At the time they started installing a newer heavy duty idler arm that was being used on the new 12,500 GVW Hummer. The two are interchangeable. Any new idler arm you receive from AMG will be the new one.

The way you check for a bad idler is to jack up the truck under the front right a-arm. Grab the tire at the 9:00 and 3:00 o'clock position and shake it back and forth. Look at the idler arm. It shouldn't move more than 5/16" of an inch (according to the shop manual) up and down. Too check the pittman jackup the left side under the a-arm. It shouldn't move more than 1/8".

I now have a 1996 TD so does one of my friends. He had the idler replaced on his truck around 10,000 miles. I decided to have mine checked so I went for an alignment around 12,000 miles and the idler arm was moving at least 3/4 to a inch. I replaced it with a new one about a week ago. Went back to the alignment shop. It too was bad. It was moving 1/2". What this means is that you can't really set the toe to any kind of tolerance. Setting the toe 1/8" in with the tires waving back and forth 1/2" doesn't make any sense. I have since received another idler and installed it Thursday. I checked it out after the install and it too seems loose. I'm wondering if there is a bad batch of new idler arms.

An interesting aside. The alignment/spring shop I took my truck to works on a lot of trucks all the way from pickups to large semi trailers. The alignment guy told me that one reason the idlers will continue to wear is because of the tie rod and idler arm geometry. The lift of the truck and the desire to keep the steering linkage up out of harms way makes it necessary to have the tie rods at a steep angle. Every time you hit a bump and the suspension moves the tie rod pushes up causing the idler to absorb and travel a greater distance in two directions. He said he sees this on Chevy pickups that are lifted and have snow plow springs installed.

I noticed that you had answered a few questions for Mike Selig. I have a 96 TD wagon with 13000 miles. I brought the truck in to have the toe checked. They couldn't do anything about the front because the idler arm was flexing 3/4". I called Lynch and they sent me a new idler which I replaced about 2 weeks ago. Thinking all was fine I brought the truck in to have the alignment checked once again. The shop showed me that the idler was still flexing 1/2". Lynch sent me another one and it too is flexing 1/2". The pittman is fine, the ball joints are ok as well as the steering box. The mechanic at Lynch said that they do around 3 idlers a week sometimes and new ones don't flex 1/2".

I suspect that there is a bad batch of idler arms. What should I do next?

I have not heard of any new Idler arms with 1/2" play out of the box. It is possible that the shop is using too much force to check the arm. The specification is 1/8" up and 1/8" down for a total of 1/4" play using a spring scale within 2" of the arm and at 50 lbs. tension.

This specification is true for all model years and is shown in the Service Manual pre - alignment checks. I hope this helps establish the accuracy of their checks.

Doug Hamlin

Hi Dave:

Thanks for the fast response. Checking the idler using your method shows the arm is in fact good. We were using the method shown on page 8-2 in the 1996 manual. What it say's is the following:

Raise and support the vehicle under the frame and secure the steering wheel Check for looseness in the idler arm and steering arm by grasping tires at the front and rear outer edges and moving in and out. Replace the idler if the vertical motion at the center link exceeds 5/16".

When we do the above test the tires moves back and forth 1/2" and the idler moves up and down 1/2". The alignment guy said that it's kinda worthless to set the toe in to 1/8 when the wheels are moving 1/2".

What do you think? Do all the trucks' wheels move back and forth 1/2"?

The method you refer to will exceed the 50 lbs. pressure due to the leverage of the 37" tires and angles involved. Per TRW the only acceptable method is the one I described and is now shown in our manuals. There has long been some discussion about idler arms and I can take almost any vehicle with a drag link steering system and make a new idler arm look like junk. I feel that any vehicle would show some fluctuation in toe due to side loads but the settings are to establish a neutral position. This is also true of the camber or caster on any vehicle, not just the Hummer. The toe in should be set per specs and with vehicle at normal operating weight as per any alignment.


I've had problems with alignment, but never tire balance. My 95 GSA's with runflats run smooth from slow to top speed. If you're having problems with shaking at 35 to 40 your problem is most likely a shot idler arm and or a pitman arm.

When driving, as soon as the truck hits 35 mph the front would shimmy and shake like it was coming apart. It would stop at around 40. When the weather got really cold (5 degrees) the problem would diminish. Why? Because the rubber in the idler arm would stiffen up and hold the front end together. As soon as it warmed up to 25 or 30 the shake came back. I had these replaced under warranty last month. They have a new heavy duty idler arm that is designed for the new 12,000 lb. GVW Hummer that they installed. This arm is on all the trucks from 96 on up. This idler arm isn't much better then the old one. Supposedly AMG is coming out with a new design that uses a metal bearing instead of the plastic one.

To check the idler, jack the truck up under the lower control arm on the passenger side. Grab the tire at the 3 O'clock and 9 O'clock position and try to move the tire in and out. According to the shop manual if you have more then 5/16" vertical motion at the center link (long rod connecting both sides of the steering linkage) or 1/32 freeplay at the ball stud it needs replacing.

Too check the pitman, jack the truck up under the lower control arm on the drivers side. Grab the tire at the 3 O'clock and 9 O'clock position and try to move the tire in and out. According to the shop manual if you have more then 1/8" vertical motion at the center link or 1/32 freeplay at the ball stud it needs replacing.

There's a good chance if your idler is shot your pitman will be also.

You can check the ball joints by grabbing the tire at the top and bottom and try moving the tire in and out. Replace the uppers if the movement at the top outer edge of the tire is 3/8" or more. Replace the lowers if the movement at the bottom edge of the tire is 1/2" or more. On a truck with good ball joints there will be no movement at all.

Chuck 98td

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