13 speed downshifting tips?

I use it from a stop when bobtailing but that's about it.

 

I'll sometimes use it on a steep hill when I want to get out of low range. It gets me onto the high side with just a shade higher ratio and now I can split and crawl my way up that bugger 200 rpm at a time.

I believe the term is "overlap"

 

Hi GasHauler, ah yes, we called it the "mystery gear". 25 (2)+2 got it, granny (or 1st gear) in high range. Usually empty, or bobtail, it eliminated going into the low side going around a corner, coming up on a traffic light that just turned green. Generally, not while loaded.High range reverse was another one when bobtailing.

 

Man whenever the truck stop is full I use high range reverse and make my own spot

 

Always liked the 2 stick Mack. 5 speed reverse. Hard to back a trailer much past 2 though.

 

Hi 1johnb, do you mean the 2 stick 6 speed? The 1st T/T I drove was a '75 R model Mack with the 6 speed. The boss made it clear to me that high/low/reverse stick was NOT a splitter, although, I think some guys did it anyway. That truck rode so rough (with a 24 ft dump trailer) the main stick would jump out of gear. I had to have a tarp strap around it.

 

May have been 6 speeds, if I recall it was high low & reverse. I was in the shop but got some seat time in them. We had a 69, 78 & 79 R models. We upgraded the rears to 38000 camel backs. Yes they were stiff especially with an empty fuel trailer.

 

13 speeds are great. What I did on a hill was click the splitter back then very quickly let off then got back into the throttle, enough to break torque and then rev it 250 or 300 rpm, then when it was positively in gear got back into the throttle all the way. Took less than a second all told, and more graceful than an automatic. Takes some practice, really need to get a feel for the fuel pedal in the particular truck, but makes for a split-second shift and keeps you in the part of the power band that's best for hills. Needs to be really fast if you have a high running gear like a 3.55 or faster, and the hill is steep. My advice to the OP is to really get a feel for the fuel pedal.

A mechanic who works on our trucks had some old Macks and Autocars on his lot with twin sticks the other day when I dropped off a truck for service. Some local lumberyard is still running them, they're '84 or so models with only 100,000 miles on them (I poked around a little). I've always wanted to drive a twin-stick, just to have done it, so hats off to you guys who had to learn on them. I used to drive old Macks that had 5 speeds - the guy I worked for was such a cheapskate that he spec'd tractors with 5 and 6 speeds, no auxiliary box or anything. All mechanical. He'd load the trailer to the hinges with 100-lb burlap sacks of coffee beans - you were in 5th gear at 25 mph, it took all day to get up to speed on the highway, on flat ground. Some of the cabs only had a 237 mack engine - you might get up to the speed limit on the turnpike if you found a downgrade, and the weight pushed you up to 2300 rpm. I really could have used a second stick in those things. They also had the huge roulette wheel that you couldn't fit your hand between it and the driver's door - only took one time spinning the wheel around with the window open and almost breaking my finger to stop that habit. Least environmentally friendly trucks I've ever driven, you couldn't see behind you for a city block after taking off at a green light. Anyway, they're making it too easy these days with automatic trans and plastic trucks, so hats off to the OP for learning a 13 speed. Another few years and these things will drive themselves.

 

Hi DD, I did that too with 13 speeds on a downshift in a main gear, almost like an automatic. Regarding the 2 sticks, it is cool for a while, but gets pretty tiresome after a while. The 1st heavy duty truck I drove was a IH R-190 tandem dump truck (with no rear springs, just rubber pads) with a 450 cube (not hp) gas motor with a set of sticks, and shifting that thing was a constant chore. Someone said 2 sticks were outlawed in new trucks, not sure if that's true, but you never see them anymore. Regarding the 5 or 6 speed Macks, your boss wasn't being cheap, the "Maxidyne" high torque rise engine, was developed with an operating range of 1200-2100 rpm, and a 5 or 6 speed was standard equipment. I've driven many Macks and never had a problem with the driveline, ever. They were truly the toughest trucks out there.