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.
1988 Chevrolet Hi-Cube 5.7 M, 475/M40FACTORY OEM SERVICE PROCEDURE
Throttle Valve Control Pressure Check
- Install pressure gauge on transmission line pressure tap. See Fig 1 . Install tachometer on engine. Apply parking brake. Ensure engine is at normal operating temperature.
- Operate engine at 1000 RPM. With gear selector in "P" position, note oil pressure reading. Move gear selector to "D" position, and note oil pressure reading.
- Oil pressure "D" reading must be equal to "P" reading or must not exceed it by more than 10 psi (.70 kg/cm). Operate engine at 1400 RPM. Oil pressure should increase. Adjust throttle valve cable if pressure does not increase. See appropriate TRANSMISSION SERVICING - A/T article in the AUTOMATIC TRANSMISSION SERVICING section.
Factory Service Tools
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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.
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