1985 MACK R Model (R686ST) Twin Stick Shifting forward and reverse

The Mack has a twin stick Maxitorque Extended Range 6 speed transmission. The left stick is the “Main” and consists of neutral and gears one through five. The right stick is “Compound” (I referred to it as high and low) and that consists of reverse, Lo & Direct (high).

Although physically, I can shift one through five in low as well as direct, Mack does not recommend doing this. Mack designed this transmission to go forward in low first gear and then moved the compound or right stick from low to direct and then continue after that shifting the main transmission or also known as the left stick through the remaining five gears.

There isn’t a splitter and because the gear ratios are so close to each other it’s impossible to shift the right and left sticks as if one of them is a splitter.

From what I found through research of this transmission, the reason Mack  doesn’t recommend shifting one through five while in low is because the torque is too strong and can wear out the gear teeth in the transmission under a heavy load.

This is why it’s basically a granny gear and then four more gears after that. So it’s a total of six because you start in first low, and then shift to first direct, and then second direct, third direct, fourth direct, and fifth direct which equals six total.

Reverse is taking the Compound (right stick) and push it towards the dash and to the left. Then it is acceptable to shift one through five and have five different reverse speeds. Also, to run the winch or the PTO, put the compound stick in neutral, and then shift one through five on the main stick. That gives me 5 different speeds for the winch.

I can also put the compound stick (on the right) in direct/first and then and shift as a five speed.