| Subject: | High Pitched Whistle Noise on Turns with 700 Series Gearbox |
| Models: | 2003-2005 Chevrolet 2500/3500 Silverado |
| 2003-2005 Chevrolet Suburban |
| 2003-2005 GMC 2500/3500 Sierra |
| 2003-2005 Chevrolet Express Van |
The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in the PI.
Condition/Concern:
Owners may comment of a high pitched whistle noise coming from the steering gear while turning. An offset drilled oil return hole in spool valve has been found to be the source of the noise. The whistle noise is mainly on left hand turns. This only
applies to the 700 series gear box.
Note: To properly identify a 700 gearbox, the stubshaft is held in place by a threaded retainer and lock nut, SI Document # ID 1551804. A 680 gearbox uses a stubshaft housing that is attached with 4 mounting bolts, SI Document #
ID 725682. A 670 gearbox also uses a stubshaft housing but is only retained by 3 mounting bolts, SI Document # ID 415118.
Recommendation/Instructions:
To correct this concern, install a power steering adapter (P/N 26109078) between the power steering gear and the high pressure hose.
If the noise is not corrected by installing the adapter, replace the steering gear with a new gear for GM SPO parts. Current SPO parts contain known good stock.
All models listed built after January 14, 2005 have the revised steering gear box
Please follow this diagnosis process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.
