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Allison Transmission Parts

Troubleshooting Charts For Allison Transmissions AT / MT (B) / HT / V
The troubleshooting information contained in the following charts outlines the possible causes of transmission conditions and their remedies. Several possible causes are indicated; numbered items indicate suggested remedies for the causes. For Sales and Service Call America's #1 Supplier of OEM Allison Transmission Parts and Authorized Allison Dealer;
TransDiesel Transmission Call us: 1-407-295-1221

E - LOW PRESSURES
Condition Probable Causes Suggested Remedies
Low Main Pressure in All Ranges 1. Transmission fluid level low. 1. Add transmission fluid to the proper level. (Be sure dipstick calibration is correct for specific model.)
2. Filter element clogged. 2. Replace filter or element.
3. Sealring on transmission fluid intake tube damaged or missing. 3. Install new sealring onto the top end of the intake tube.
4. Main-pressure regulator valve spring weak. 4. Replace spring.
5. Control valve body leaking. 5. Replace or rebuild control valve body assembly. Take care when removing valve body components to properly label the components for proper reassembly.
  6. Valves sticking (trimmer relays and main-pressure regulator). 6. Replace or rebuild control valve body assembly. Take care when removing valve body components to properly label the components for proper reassembly.
  7. Input charging pump worn or damaged. 7. Replace or rebuild pump.
  8. Priority valve missing. 8. Replace missing valve.
Low Main Pressure in First Range, Normal Pressure in Other Forward Ranges 9. First range circuit leaking in control valve body. 9. Replace or rebuild control valve body assembly.
10. First clutch piston seals leaking. 10. Overhaul transmission; replace piston seals.
Low Lubrication Pressure 11. Transmission fluid level low. 11. Add transmission fluid to the proper level. (Be sure dipstick calibration is correct for specific model.)
12. Engine idle speed too low. 12. Refer to vehicle service manual.
13. Cooler lines restricted or leaking. 13. Check for kinks, leakage; reroute or replace lines as necessary.
14. Lubrication valve spring weak. (Not applicable for AT models.) 14. Replace spring.
15. Lubrication valve not seating. (Not applicable for AT models.) 15. Replace lubrication valve.
16. Excessive internal transmission fluid leakage. 16. Check other pressures. Check torque on valve body mounting bolts.