cecilktm

Thanks Underdog.

I don't think the type of air cleaner has anything to do with the truck being Canadian or not. R model air cleaners with two air ducts coming out the front would be an indicator that the truck had a Maxidyne 285 or 300 with tip turbine / coolpower set-up. One air duct goes directly to the intake side of the turbo and the other goes directly to the cool air side of the heat exchanger. I haven't seen any other type of Mack engine using this type of dual duct air cleaner, but I also haven't spent too much time in Canada. I only mentioned this at all because it would have been a non-typical powertrain combination to have a 12 speed transmission mounted to a Maxidyne 300 engine. The high torque and long powerband of the Maxidyne did not need so many gear ratios, and the whole selling point of the engine was to cut down on the number of gear shifts needed when accelerating or decelerating. If in fact Canadian R models had two air ducts coming out of the air cleaner for some other reason, then I'd be interested in understanding why.

If it were a "quad box" it would have 4 speeds on the auxiliary stick, 5 speeds on the main, and 18 usable forward gears total, as 220cummins shows in his post. What your dad's truck has is a "lo-hole" 6 speed, which means it also has a Maxidyne 237 engine, both available for the first time in 1966 (the Maxidyne 300 engine did not debut until 1973) EDIT - I JUST SAW YOUR PREVIOUS UPDATE ABOUT YOUR DAD CHANGING OUT THE ORIGINAL HEATER COVER AND REPLACING IT WITH ONE THAT HAD THE "LO-HOLE" SHIFT PATTER STICKER...... I IMAGINE THAT WOULD BE QUITE A SITUATION IF SOMEONE TRIED TO SHIFT THE QUADRUPLEX TWIN STICKS USING THE LO HOLE SHIFT PATTERN

Looks like a 12 speed with the extended range on the extra stick instead of a dash switch (see shift pattern below). Also, looks like the truck has a Maxidyne 300 based on the air cleaner, assuming it's original. In lieu of the the typical 5 or 6 speed lo-hole, it's got to be the less common 12 speed paired with the Maxidyne.