I'm not a trucker and my little car has only five speeds forward and one reverse... but this thread has captured my interest and is fun reading. Thanks for posting the questions, slim... and thanks to all who are responding. You guys know your ####!
And now? I'm off to youtube to find those clips...
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the one i drove we used for hostling containers around the yard, so i don't remember ever getting the A box out of 1st, and the B box had a funny shift pattern. 1st was left and up, 2nd was left and back, 3rd was a horseshoe shift over to right and back, then 4th was right and up. i always had fun driving that thing.Ducks Thanks this.
That "mail box flag" that dropped in front of the driver's windshield was a low air warning.
Dwight Phillips wrote an article in the Sep/Oct 2008 issue of Wheels of Time titled "Missing the long haul after a life on the road". He begins with a description of a Model T Ford farm truck. The truck had 14 speeds forward and seven in reverse. Phillips wrote, "This was accomplished by the addition of a 3-speed transmission and a 2-speed rear end to the standard 3-pedal set-up. The left pedal, when depressed, was low, and when let up was high with neutral in the middle. Put the transmission in low and depress the pedal and you had one gear. Letting the pedal up gave you the next gear. Going through the three gears in the transmission gave you six speeds forward. Shifting the rear end to the high side and going back through the transmission again gave you another six speeds forward. If you put the transmission in reverse and depressed the center reverse pedal it would go forward, shift the rear end and you had another forward speed. ...I'm not saying that some of the gears didn't overlap with the same speed."
And we thought we had it rough.
This brings back some memories. Being a retired Navy Seabee Equipment Operator we had 5X4's for along time. Our road tractors were Jimmy's with 318 Detroits up until they started to get replaced around the late 80's. I believe the thinking behind that type of transmission was they were just about indestructible and we pulled alot of heavy loads with small power.
Fortunately, I was taught by some old timers before I went into the service how to drive these antiques and I remember 2 key issues. Always shift the main first and NEVER stick your arm through the steering wheel. I know some have already stated about the steering wheel but I can tell you if you blow a front tire or even hit a hole in the road that steering wheel can break your arm like a twig. If you have power steering it might save your arm but the roads (or I should say the no roads) that I have had to haul bulldozers and track loladers and such on had some holes that nothing would help.
You select the main then split the gears. You basically have to do what a 13 or 18 speed does but with another stick. You might have a 4X3,4X4,5X3,or 5X4 or a couple of others. But they're basically the same when it comes to shifting. Like 1st main then aux 1,2,3,or 4, then second main with the aux back down to 1. Then aux, 1,2,3,or 4 and so on. To down shift-Down shift the main to the next low gear bring the rpm's back up and shift the aux to 3, or 4 then 2, 1, then shift the main again. East right!
You don't have to use every gear and you'll want to select the lowest gear that will move the truck with no applied power. Plus, after awhile you'll find out you don't want to miss a gear when pulling a grade!
GasHauler, I respectfully disagree with your statement about always shifting the main transmission first. Quote: "To down shift-Down shift the main to the next low gear bring the rpm's back up and shift the aux to 3, or 4 then 2, 1, then shift the main again."
For example, you are climbing a grade and have downshifted the auxiliary transmission to underdrive or low with the main transmission in 5th. You want 4th in the main transmission, but you would have to rev the engine way above the operating rpm range unless you begin the split shift by shifting the auxiliary to overdrive as your first move. As a practical matter, you may be skipping overdrive and going for direct, but whatever, the transmission to be upshifted is shifted first. The reason is that you can always drop the engine rpm, but you can never accelerate beyond the governor. They won't go into gear if rpm does not match road speed.
Some drivers are "granny shifters". With that technique, the driver leaves the auxiliary in underdrive or low until he reaches high gear in the main transmission. Only then does he shift the auxiliary. He never split shifts and he never makes a mistake.
We have a 72' binder dumptruck at work, that rarely leaves the yard, but I have taken it out on the road in the past. The motor is a 6-71 screamer, backed by a 4x4 spicer airshift.
basicly, the second tranny is shifted by a rotary selector on the knob. You rotate it clockwise, from N-1-2-3-4
the pattern is
1-1,1-2,1-3,1-4 then you hit second gear in in the main tranny,
2-2,2-3,2-4, then third
3-2,3-3,3-4, then fourth
It's really a very, very fast shifting tranny.. unlike the truck which tops out at around 52mph..
Thanks for all the replies! Though I have to admit I'm still a little confused though I get the idea. What confuses me the most, when you shift both the main and aux...Do you need to adjust the RPM when shifting the aux AND the main...like let the RPM drop, shift one box, blip the throttle, shift again? And when downshifting? I couldn't imagine how nightmarish it would be to lose a gear with one of these things.
I find it so incredible that at one time drivers could do this type of thing in their sleep. And now with automatics some drivers would be confused with a 10 speed! I guess I like a challenge and would really like to learn a 5 and 4. The drivers I knew who could handle them they just loved them for the versatility, and the funny thing was one of them was a pretty young guy, not an old timer who grew up on them.
Shifting sequence for 5x4 with enough HP to pull it...Start Main in 1st, Aux in 1st. move Aux to 2nd, then move Main to 2nd, move Aux to 1st, then 2nd. move main to 3rd (which is "around the corner"), move Aux to 2nd, the around the corner to 3rd (if trans uses rods make sure you make a square corner or you will be along side the road with the shift tower boot off and a crowbar moving the shifter slides) then move main up against the dash, Aux to 2nd, 3rd then up against the dash. Man I wish still had a set of sticks !!!!!
The first truck I drove was an old Pete cabover with one of these transmissions. I think the old man made me drive it so I would learn it first. Didn't know how hard I had it till I drove his K100 for the first time.
Mack made a 9 speed, & 10 speed, Duplex. 13 speed, & 15 speed, Triplex. 18, speed, & 20 speed Quadraplex.
They also made a 6 speed, & 12 speed with two sticks. The transmissions were designed to be shifted with one hand. The best thing about the Mack transmissions was the cases were bolted together, eliminating the use of a jack shaft between the boxes like most of the other combinations.
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