3–30 Copyright © 1996 General Motors Corp.
AT 500, 1500 SERIES AUTOMATIC TRANSMISSIONS
C. Low Pressure
Low main pressure in all ranges Low fluid level. Add fluid to the proper level. Refer
to Paragraphs 3–4 through 3–10.
Filter element(s) clogged. Replace filter or element(s). Refer to
Paragraph 3–10.
Sealring on intake tube leaking or
missing.
Install new sealring onto the top end
of the intake tube. Refer to Para-
graph 7–10b.
Main-pressure regulator valve spring
weak.
Replace spring. Refer to Paragraphs
6–7a and 6–7d.
Main control valve body leakage. Replace or rebuild main control
valve body assembly. Refer to Para-
graph 6–6.
Valves sticking (trimmer relays, and
main pressure regulator).
Replace or rebuild main control
valve body assembly. Refer to Para-
graph 6–6.
Input charging pump worn or dam-
aged.
Replace or rebuild pump. Refer to
Paragraphs 5–3i, 6–7, and 7–8b.
Missing priority valve. Replace missing valve. Refer to
Paragraphs 6–6a and 6–6b.
Low main pressure in first range,
normal pressure in other forward
ranges
First range circuit leakage in control
valve body.
Replace or rebuild main control
valve body assembly. Refer to Para-
graph 6–6.
Excessive leakage at first clutch pis-
ton seals.
Overhaul transmission. Replace pis-
ton seals.
Low lubrication pressure Low fluid level. Add fluid to the proper level. Refer
to Paragraphs 3–4 through 3–10.
Engine idle speed too low. Refer to vehicle service manual.
Cooler lines restricted or leaking. Check for kinks or leakage. Reroute
or replace lines as necessary.
Excessive internal fluid leakage. Check other pressures in this chart.
Also check valve body mounting
bolts. Refer to Paragraph 7–10a.
Table 3–13. Troubleshooting Chart (cont’d)
Problem Probable Causes Suggested Remedies
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