Alignment - Lead/Pull, Torque/Memory Steer: Overview

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NUMBER: 92-T-20

CORP. REF. NO.: 073002R

DATE: December 1991

SECTION: 3


SUBJECT LEAD/PULL, TORQUE/MEMORY STEER,
STEERING WHEEL OFF CENTER
- DIAGNOSIS AND REPAIR

MODELS/YEARS 1982-88 FIRENZA,
1982-91 CUTLASS CALAIS,
1992 ACHIEVA


This bulletin cancels and supersedes Dealer Technical Bulletin 90-T-140 which should be discarded.

Figure 3:

The following diagnostic and repair information has been developed and compiled to assist dealer service personnel in their efforts to diagnose and correct vehicles exhibiting lead/pull, torque steer, memory steer, steering wheel off-center, and/or unusual tire wear conditions. A flow chart which will be helpful in understanding the logic of the diagnostic and repair procedures is included (Figure 3).


DEFINITIONS
Lead: On a smooth, flat road with the transaxle in neutral, the vehicle does not require a noticeable torque input to the steering wheel to maintain a straight path. However, with hands removed from the steering wheel, the vehicle drifts to the left or right.

Pull: On a smooth, flat road with the transaxle in neutral, the vehicle requires a noticeable torque input to the steering wheel to maintain a straight path. A pull requires noticeable input to correct.

Note: "Leads" and "pulls" are different terms for the same condition. Lead refers to the path deviation (usually a lane change in 0.2 miles or less); pull refers to the torque at the steering wheel required to maintain a straight path (more than 0.3 N-m or 2.7 lbs.in.).

Torque Steer: On a smooth, flat road the vehicle has a left or right steering force that is eliminated when the transaxle is placed in neutral. The magnitude of the steering force is usually (but not always) dependent on the amount of applied engine torque. Torque steer at constant highway speed is frequently mistaken for leads/pulls.

Memory Steer: On a smooth, flat road the vehicle exhibits a slight lead/pull condition when the vehicle is returned to a neutral or straight ahead position after completion of a turning maneuver. This condition is always noted as being in the same direction as the last turning maneuver (after a right turn, the vehicle leads or pulls to the right; after a left turn, the vehicle leads or pulls to the left), and may vary in degree right to left. This condition is most noticeable with the driver's hands off the steering wheel.

Steering Wheel Angle: The "levelness" of the steering wheel when following a straight path. Steering wheel should appear to be level with the instrument panel when going straight ahead, and within +/- 5 degrees when measured on an alignment machine.