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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

N - CLUTCH(ES) SLIPPING - MT(B) 640/643/650/653* Condition Probable Causes Suggested Remedies Slipping in First and Reverse Ranges Only Slipping in second or Third (MT 640, 643) or Third or Fourth (MT 650, 653) Only 1. First clutch defective. 1. Overhaul clutch and replace piston seals. 2. Clutch for particular range defective. 2. Overhaul clutch and replace piston seals. Slipping in Fourth and Reverse Ranges Only 3. Fourth clutch defective. 3. Overhaul clutch and replace piston sealrings.   4. Sealrings on center support hub worn or broken. 4. Replace sealrings. Slipping in Low Range Only (MT 650, 653) 5. Low clutch defective. 5. Overhaul clutch and replace piston sealrings. Slipping in All Forward Ranges 6. Centrifugal check valve stuck open (forward clutch). 6. Inspect check valve for contamination and proper operation. 7. Trimmer valve stuck (selected range.) 7. Overhaul trimmer valve. 8. Piston seal damaged. 8. Replace piston seals. * NOTE: If unit is modified for split shaft PTO, all external circuitry must be removed before troubleshooting.