GM Service Manual Online
For 1990-2009 cars only

Using the Clutch

When you are starting to move the vehicle, it is important to begin with the engine speed at idle. Then start to engage the clutch and listen for an engine speed drop of about 100 rpm. At this point, the clutch is engaging, so you should increase the engine speed and fully engage the clutch. It is important not to increase the engine speed sooner or before the clutch begins its engagement. If you do, you can cause damage to the vehicle.

Double-Clutching

You must use the double-clutching method when you shift an unsynchronized gear set. Disengage the clutch, shift to N (Neutral) and engage the clutch. When upshifting, slow the engine until the engine rpm and road speed match. When downshifting, accelerate the engine until the engine rpm and road speed match. Then quickly disengage the clutch and move the shift lever to the next gear position and engage the clutch.

Eaton® Fuller® Five and Six-Speed Transmissions and TTC Spicer Seven-Speed Transmissions

These transmissions have gears that automatically synchronize when you shift up or down (except 1 (First) gear on the five-speed and seven-speed transmission which is unsynchronized). Choose the gear that will maintain the road speed you want while keeping the engine above two-thirds of the governed speed. When the engine speed drops below two-thirds of the governed speed, shift into the next lower gear before your engine begins to lug. When you shift down, be sure to double-clutch if required.

Eaton® Fuller® Nine and Ten-Speed Non-Synchronized Manual Transmissions

If the vehicle has one of these transmissions the engine rpm and road speed must match when upshifting and downshifting. The label above the windshield will tell you the operating basics you need to know.

The following are driving tips.

    • Always choose an initial starting gear suitable for the load and terrain.
    • Always use double-clutching procedures when shifting.
    • Never move the range shift lever to the LO speed gear position after HI range preselection, or anytime the transmission is in the HI range.
    • Never move the range knob or lever with the shift lever in N (Neutral) while the vehicle is moving.
    • Never make a range shift while moving in R (Reverse).

Clutch Brake (Vehicles with Non-Synchronized Transmission)

A clutch brake is used to stop transmission input shaft rotation so that 1 (First) or R (Reverse) gear selection can be initiated when the vehicle is at a standstill and the engine is idling.

Press the clutch pedal all the way down to the floorboard to apply the clutch brake.

When using the clutch brake, disengage the clutch pedal and shift the transmission into either the initial starting gear or R (Reverse). If the tooth-butting occurs between the clutching teeth, re-engage the clutch while applying light pressure to the shift lever. This will provide for a smooth shift into either 1 (First) or R (Reverse) gear.

Notice: Using the clutch brake for shifting into any gear other than 1 (First) or R (Reverse) may cause premature wear of the clutch brake and make gear shift effort more difficult. Do not use the clutch brake for shifting after engaging 1 (First) or R (Reverse).