Info - Effect of Steering Box Limiter Adjustment on Turning Radius and Possibility of Power Steering System Damage Due to Improper Adjustment
| Subject: | Effect of Steering Box Limiter Adjustment on Turning Radius and Possibility of Power Steering System Damage Due to Improper Adjustment |
| Models: | 1990-2002 Chevrolet C-Series (H Model) Medium Duty Conventional Trucks |
| 1990-2002 Chevrolet T-Series (F Model) Medium Duty Tilt Cab Trucks |
| 1990-2002 Chevrolet B6-7 Model School Bus |
| 2003-2004 Chevrolet Kodiak C4500-C8500 Series Trucks Built Prior to July 2, 2004* |
| 1990-2002 GMC C-Series (H Model) Model Medium Duty Conventional Trucks |
| 1990-2002 GMC T-Series (F Model) Medium Duty Tilt Cab Trucks |
| 1990-2002 GMC B6-7 Model School Bus |
| 2003-2004 GMC TopKick C4500-C8500 Series Trucks Built Prior to July 2, 2004* |
| *Trucks built after July 2, 2004 have non-adjustable limiters. |
This bulletin is being revised to add a build date to the C4500-C8500 Series Models. Please discard Corporate Bulletin Number 03-02-32-044 (Section 02 - Steering).
Improperly set steering gear box limiters may result in an inoperative steering gear box pressure relief valve. In other words, a valve that activates prematurely, giving the impression that the vehicle has a tighter turning radius in one direction than the other, or steering system components damaged by excessive power steering pump pressure.
The purpose of the steering limiters is to reduce the assist pressure when the linkage nears the stops of the knuckle. This prevents damage to the steering components. Automatic adjustment occurs, if, using the steering wheel, the steering gear is slowly articulated in either direction until the maximum steering lock or axle stop is reached.
Automatic self-adjusting steering gear box limiters are one-way sliding sleeves. They can adjust shorter to accommodate a steering stop readjustment for a tighter turning radius but have no capability to go longer.
A limiter adjustment will be required under the following conditions:
| • | When installing a new steering gear box. |
| If limiters are not properly reset before starting the engine, the technicians might see a loss of assist pressure before the axle stops are reached. This might be misdiagnosed as an inoperative service gear. |
| • | When readjusting axle stops in order to achieve a tighter turning radius. |
| Steering limiters will have to be collapsed a little further to accommodate the new linkage position. |
| • | When adjusting axle stops to achieve a wider turning radius. |
| In this case, the limiters must first be replaced (refer to End Limiters Replacement in SI) and then readjusted using the procedure described below. |
Use the following procedure to adjust the limiters on the steering gear box.
Important:
• This procedure applies to both the TRW Ross and ZF steering gears. It
does not apply to the Saginaw 710 gear. • TRW Ross steering gears are used on 10K, 11K, 12K, 13, 220, 14, 600 and
16K front axles on the 1990-2002 C-Series and 1993-2002 B6-7 school bus. • ZF gears are used on T-Series tilt cab trucks and 2003-2004 C4500-C8500
Series for all axle applications.
Important: If in making a readjustment, the technician goes too far with the wheel stops and wants to go backward, the limiters will have to be replaced.
- Adjust the steering stops on the knuckles. Refer to Stop Screw Adjustment in SI for the proper procedure.
- Suitably raise and support the front of the vehicle so that the front tires are off the ground.
- With the engine off, cycle the steering wheel slowly in both directions until the linkage hits the axle stops.
An alternate method is to use turning platforms under the tires, if available.
The limiter hits an internal valve in the gear that will reduce the assist pressure. Articulating the steering linkage with the engine off slowly collapses the limiter to a precise length. This will provide for pressure relief at the right time.
Due to some spring back in the limiter, the pressure will start to relieve approximately 3-5 mm (0.12-0.20 in) before the linkage hits the axle stops. This is normal.
Warranty Information
For vehicles repaired under warranty, use:
Labor Operation | Description | Labor Time |
|---|---|---|
E9955 | Limiter, Power Steering - Adjust | 0.5 hr |
