Bonneville V6-231 3.8L VIN 3 SFI (1988)
FIGURE 3 - DESIGNATED HIGH ALTITUDE COUNTIES*
BULLETIN COVERS:
A harsh 3-2 detent downshift that occurs at high altitudes for some 1988 Bonneville models equipped with a 3.8L or 3800 engine and a THM 440-T4
transaxle. This condition may be corrected by replacing the 3-2 control valve spring (341) shown in Figure 2. Refer to Figure 3 for areas designated as
High Altitude Counties in the continental United States.
Prior to replacing the 3-2 control valve spring, other items to be inspected that affect transaxle operation and may contribute to harsh shift conditions are:
-
Vacuum leaks (low vacuum supply to the vacuum modulator). Required vacuum is 44-61 kPa (13-18 in. Hg.)
