10 - 12 Speed Confusion

[ThaddeusW]

Ok I see there are a few different names for the old 10 and 12 speed transmissions. First there is the two stick ten speed, 12 speed extended range and plain 12 speed.

I thought the two stick 10 speed had a lo/direct compound stick and 1-2-3-4-5 with a hi-lo-N-rev air switch on the main. 10 foward gears, 5 rev gears with 1st used in lo on the compound for two crawler gears. 12 speeds foward speeds in total. Is this also called the 12 extended range? The model is TRTXL1070.

The other 12 speed I know of has a single stick with 1-2-3-4-5-6 and hi-lo-N-rev on the air switch. You split each gear to 6 for 12 foward gears and 6 reverse gears. What model transmission s that? TRXL1270? Newer mack transmission model numbers confuse me.

[chris88]

I never quite understood how the figured out the 12 speed to be a 12 speed, a 5 speed main box and a low and high split and then air shift reverse. and then a compound low in the front box.

[HK Trucking]

I never quite understood how the figured out the 12 speed to be a 12 speed, a 5 speed main box and a low and high split and then air shift reverse. and then a compound low in the front box.

You could use the 5 speeds with the air splitter in low or high, that's 10 speeds, then with the front compound in Lo Lo you could use 1st gear with the air splitter in low or high for 2 more speeds, total of 12 speeds.

[chris88]

Alright i got it now. I never thought of spliting the back box with the front in low. Those damn 12 speeds are huge. Ive pulled a few out and everytime i do its almost intimidating. An 8ll looks like a toy sitting next to a 12 speed mack.