3–26 Copyright © 1996 General Motors Corp.
AT 500, 1500 SERIES AUTOMATIC TRANSMISSIONS
A. Abnormal Automatic Shifts (cont’d)
Shifts occurring at too low speed —
full throttle
Governor spring weak or missing. Replace governor. Refer to Para-
graphs 5–3e and 7–10a.
Mechanical actuator kinked, bro-
ken, or not properly adjusted.
Replace, adjust, or repair cable. Full
actuator control cable travel must
correspond with full throttle (push or
pull system). Refer to the latest edi-
tion SA1321, AT Mechanic's Tips.
Shift signal valve spring adjustment
too loose.
Tighten spring adjusting ring to
specification. Refer to Paragraph
3–13.
Modulator valve stuck open. Check spring adjustment. Clean or
replace modulator valve. Refer to
Paragraphs 6–6a(5) and 6–6b(16).
Rough shifting Governor valve malfunctioning. Clean or replace governor screen
and/or governor. The governor may
be disassembled for cleaning and
inspection only if the kit consisting
of two governor weight pins and
cover gasket is available. Refer to
Paragraphs 5–3e, 5–3h(5), 6–5,
7–10a, and 7–11a.
Vacuum modulator valve spring not
properly adjusted — vacuum hose
kinked or leaking.
Check spring adjustment. Replace
hose. Refer to Paragraph 3–13.
Mechanical actuator cable kinked,
broken, or not properly adjusted.
Replace, adjust, or repair cable. Full
actuator control cable travel must
correspond with full throttle (push or
pull system). Refer to the latest edi-
tion of SA1321, AT Mechanic’s
Tips.
Mechanical actuator malfunctioning. Replace actuator.
Vacuum modulator failed. Replace vacuum modulator. Be sure
that O-ring is installed and that the
modulator vacuum fitting is facing
forward and positioned 10° below
horizontal. Refer to Paragraphs 5–3c
and 7–11b.
Table 3–13. Troubleshooting Chart (cont’d)
Problem Probable Causes Suggested Remedies
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