How do you shift 8 speed transmission?

If it is an eight speed in a truck, chances are it is a big rig of some sort. Push the clutch in and put the shifter in first gear. Slowly let off the clutch until the truck starts to move. Speed up until it feels like you need to shift again. You can slip the shifter out of first and into second without using the clutch if you are quick and get the feel of the engine RPMs. If you want to use the clutch you will need to double clutch. Push the clutch in to shift from first to neutral. Now let the clutch out so the engine and transmission gears start turning at the same speed. Now, quickly clutch again and shift into the next gear. let off the clutch and accelerate again. If you have a four speed with a two speed rear end there will be a switch on the shifter. Shift through the first four gears normally, then flip the switch an go back to 1st, which will become 5th gear with the axle in high range.

To down shift you should double clutch too. First, clutch to shift into neutral. Let off the clutch and rev up the engine so the RPMs are correct for the vehicle speed and the next gear you want to shift into. Now clutch again and downshift. When you let off the clutch the engine, which can only turn so fast, will pull the truck speed down. You can give the engine some throttle and slowly back off so the engine braking isn't so rough or sudden. Good Luck!