Table 2-1.--Allison Four-Speed Automatic Transmission Troubleshooting Chart
TROUBLE
PROBABLE CAUSE
REMEDY
Automatic shifts at too high a speed
1. Governor valve stuck
1. Clean or replace governor
2. Modulator cable adjustment
2. Adjust cable
Automatic shifts at too low a speed
1. G governor valve stuck
1. Clean or replace governor
at full throttle
2. Governor spring weak
2. Replace spring
1. Add oil to proper level
1. Low oil level
Low main pressure in all ranges
2. Replace filter
2. Oil filter element clogged
3. Install new sealring
3. Sealring on oil pickup tube leaking
or missing
4. Main-pressure regulator Valve spring
4. Replace transmission
weak
5. Control valve body leaking
5. Replace transmission
6. Valves sticking
6. Replace transmission
7. Oil pump worn or damaged
7. Replace transmission
1. Replace transmission
1. First gear circuit of control valve
Low main pressure in first gear,
body leaking
normal pressure in other forward
ranges
2. Excessive leaking at first and reverse 2. Replace transmission
piston seals
Add oil to proper level
1.
Low oil level
Intermittent buzzing noise
1.
Replace intake pipe seal and filter
2.
Air leak at oil intake pipe
2.
Replace filter
3.
Clogged filter
3.
Improper oil level, or improper or
4.
Aerated oil
4.
contaminated oil
Excessive creep in first and reverse
1. Engine idle speed too high
1. Adjust idle speed
Low lubrication pressure
1. Oil level too low
1. Add oil to proper level
2. Excessive internal oil leakage
2. Check other pressures above; check
valve body mounting volts
3. Check for kinks, leakage; replace
3. Cooler lines restricted or leaking
lines if necessary
1. Refer to vehicle service manual
Oil leaking into converter housing
1. Leaking engine crankshaft rear oil
seal
2. Charging oil pump, lip-type seal at
2. Replace pump seal
torque converter, leaking
3. Leaking sealring around body of oil
3. Replace transmission
pump
4. Cracked weld in converter assembly
4. Replace converter assembly
leaking
Add oil to proper level
1.
Oil level low
Transmission heating up in all ranges 1.
Drain oil to proper level
2.
Oil level high
2.
Refer to vehicle service manual
3.
Engine cooling system restricted
3.
Clean or replace lines
4.
Oil cooler lines restricted
4.
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