Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
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HOMESERVICE MANUALSCHEVROLET1987FORWARD CONTROL 4.8 T, AUTOMATIC, 400/M40REPAIR AND DIAGNOSIS (SINGLE PAGE)TRANSMISSIONAUTOMATIC TRANSOVERHAUL - THM 400TESTINGROAD TEST
1987 Chevrolet Forward Control 4.8 T, Automatic, 400/M40
Road Test
1987 Chevrolet Forward Control 4.8 T, Automatic, 400/M40SECTION Road Test
- Connect tachometer to engine. Place selector lever in "Drive" range and accelerate vehicle from standstill at minimum throttle opening.
- The 1-2 and 2-3 upshifts should occur as vehicle reaches correct speed. As vehicle speed decreases, 3-2 and 2-1 downshifts and engine braking effect should be noticed. See SHIFT POINT SPECIFICATIONS .SHIFT POINT SPECIFICATIONS
Application Speed (MPH) Upshift Minimum 1-2 15 2-3 30 Detent Downshift Minimum 3-2 68-73 2-1 28-32 Upshift Maximum 1-2 44-48 2-3 77-83 - Stop vehicle and place selector lever in "2" (Intermediate) range. Accelerate from standstill. Upshift 1-2 should occur at all throttle openings (shift point will vary with throttle opening). The 2-3 upshift should occur. Stop vehicle and place selector lever in "1" (Low) range. Accelerate from standstill. No upshift should occur.
- With selector lever in Drive range and vehicle speed at 35 MPH, move selector lever to "2" (Intermediate) range. Transmission should downshift to 2nd gear. Increase in engine RPM and engine braking effect should be noticed.
- With selector lever in "2" (Intermediate) range and vehicle speed at 25-35 MPH (not over 40 MPH), move selector lever to "1" (Low) range. Throttle must be in closed position. Transmission should downshift to 1st gear. Increase in engine RPM and engine braking effect should be noticed. Stop vehicle and place selector lever in Reverse. Check for reverse operation.
CLUTCH & BAND APPLICATIONS
| Lever Position | Elements In Use | |
|---|---|---|
| "D" Drive | ||
| First | Forward Clutch & Low Roller Clutch | |
| Second | Forward Clutch, Intermediate Clutch & Intermediate Clutch Sprag | |
| Third | Forward Clutch, Direct Clutch & Intermediate Clutch | |
| "2" Intermediate | ||
| First | Forward Clutch & Low Roller Clutch | |
| Second | Forward Clutch, Front Band, Intermediate Clutch & Intermediate Clutch Sprag | |
| "1" Low | ||
| First | Forward Clutch, Low Roller Clutch & Rear Band | |
| Second | Forward Clutch, Front Band, Intermediate Clutch & Intermediate Clutch Sprag | |
| Reverse | Direct Clutch & Rear Band | |
| Neutral Or Park | All Clutches And Bands Released Or Ineffective | |
RENDER: 1.0x
NO RELATED
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.