Twin Stick Transmission Shift Patterns

[HeyCharger]

better check and see what a real DUPLEX is. i think you're getting your two sticks mixed up.

←

Hi TSM, please enlighten me as to "what a real DUPLEX is".

I was only quoting from various Mack manuals.

Rod. (always eager to learn).

[b61fred]

Hi,

I have two trucks with duplex transmissions, one is a trd720, the other is a trd72. I will start with the trd720, this is simple, 5 speed box with low and direct rear box, this trans has 5 progressive ratios, with no overdrive, so it is shifted 1st, low then high, 2nd low then high, and so on, 10 gears... the other trans screws things up some, the front box has 5 progressive ratios BUT 4 th is direct and 5th is overdrive( also known as overgear) and has the some low and direct two speed box on the rear. This will give yo 10 gears right? well yes and no, 4th gear in direct is 1.0 to 1.0 ratio, ( input shaft turns 1 turn output 1 turn). now if you shift into 5th low the main box is in over drive( 0.69 to 1) but the low gear in the 2 speed box lowers the ratio, this will give you a ratio of 1.04 to 1 , almost the same a 4th direct, so you have no need to use this gear sence it is the same a 4th high and uses two gear reductions to get the same ratio as conecting the input shaft to the output shaft. So the the proper shift for the 9 speed overgear trans is the same as the 10 speed other than you omit the 5th low because it is a duplcate ratio. If thats not enough for you you can get into your trdx72 and trdx720 trans, these trans. have a very low gear in 1st. for heavy work, this realy misses up things, this trans you have to shift very differently than the other two. All 4 of these transmissions are duplex transmissions. So I would say that all of you are correct. I believe that is why all of these trucks have those little tags up by the sun visor, there are so many variations, it just comes down to what your truck was designed to do, and if the guy that ordered the truck knew what he was doing. Fred

p.s. the triplex and the quadraplex have some duplicate ratios also because of the overgear 5 speed front box and overdrive in the rear box.

[Freightrain]

Welcome Admiral.

As for shifting sequence. Do what ever you feel it needs. As long as it's not lugging then it's fine. I leave out gears all the time. Skip along for whatever the situation requires.

NO one can say what is right or wrong for sure. The only people right are the people that say start in the basement and use every gear, every time. No matter what. But we all know that the real world does not follow that thinking.

Have fun!

[Joe Cummings]

You should see me behind the wheel in one of my concave cab B models,Larry.

I have the same problem with those. I think if those B-67s are put together right they have a smaller wheel. But even with the right one I never could drive one far.

Joe

[Joe Cummings]

a 2 stick 6 speed is realy a 5 speed with the option of a low first gear for extream off road or heavy hauling.

the main box has 5 foward gears

the aux has revers, Low and direct

under normal use . you only shift the main stick (closest to your leg).1-2-3-4-5 the aux box stays in "Direct"

If you are very heavy or in a hole and need to climb out you would put the aux or compound box into "low" and use the main in 1st. After the truck is out of the hole mud etc...and on flat level ground you would shift the aux box from "low" to "direct" accelarate then shift 2-3-4-5 with the main. So basicly its like splitting 1st gear in half with the aux box. this gives you 6 foward speeds. However the shift from "low" to "direct" has to be done carefully as if the truck is still climbing out of a hole you likely will miss shift as the slow road speed will fall very quick.

Trent

There was also a another version of that low hole box with an extra low reduction in the compound. It was designed for concrete mixers so they could do curb pours without working the hell out of the clutch. I could get a few extra gears out of these if I shifted them right.

And then there were the "high hole" version of the 6 speed with that big heavy triple case. You went through 5 in dirrect and then shifted the compound into overdrive. I used to see these alot in DM600 & 800s with Maxidynes and rears #55,000 and greater.

[Jocko]

i used to drive a 5+4 trans in a B-model as a yard jockey this is how i drove it

1+2

then shift the main into 2

2+2 Main+Aux

2+3

2+4

then split the two sticks to 3+2

3+3

3+4

then split them into 4+2

4+3

4+4

then split into 5+2

5+3

5+4

then i was done shifting

1 4 R 2 4

Aux= /---/ Main= /---/---/

2 3 1 3 5

then in my fathers old 72 Autocar he had a 4+4+Overdrive

wich was just like a 5+4 just 5 gear was Overdrive and the gear patterns were backwards

like this

2 3 (OD) 2 4

Aux= /---/ Main= /----/----/

1 4 1 3 R

same thing except backwards hope this helps.

[Jocko]

i used to drive a 5+4 trans in a B-model as a yard jockey this is how i drove it

1+2

then shift the main into 2

2+2 Main+Aux

2+3

2+4

then split the two sticks to 3+2

3+3

3+4

then split them into 4+2

4+3

4+4

then split into 5+2

5+3

5+4

then i was done shifting

>>>>1 4 R 2 4

Aux= /---/ Main= /---/---/

>>>>2 3 1 3 5

then in my fathers old 72 Autocar he had a 4+4+Overdrive

wich was just like a 5+4 just 5 gear was Overdrive and the gear patterns were backwards

like this

>>>>2 3 (OD) 2 4

Aux=/---/ Main= /----/----/

>>>1 4 1 3 R

same thing except backwards hope this helps.

[Mike]

Yaw is makin me head hurt. An I thot a duplex wus a house wid a mudder in law next doe. As fur shiftin, we always did, me and de ol lady, not de mudder in law........... I'm a goin now.

Sta tuned fur da nxt show.

mike

[chris142]

This is me in my Petercar. 5x3. My main is near my leg and the brownie is near the passenger seat. I think your Macks are opposite. Same principle though.

[other dog]

This is me in my Petercar. 5x3. My main is near my leg and the brownie is near the passenger seat. I think your Macks are opposite. Same principle though.

to simplify everything, main in first,shift under,direct,and over in the aux ( that's low split,direct,hi split in the compound for a Mack triplex or quadruplx-same thing) . then 2nd,under,direct,over,3rd. under, direct,over,4th. under,direct,over,then to 5th. in the main with a quad,if your main is overdrive in 5th. If it's direct in 5th. shift the aux. or compound under,direct,over like the lower gears. You shift a quad. just like a triplex on the road, don't use lo-lo.

[mackdaddy]

You should see me behind the wheel in one of my concave cab B models,Larry.

twin sticks? try workin 3.........a five, a two, and a three, with 3 150rpm splits. And as you can see.......there is no belly room. Mack got it right on this one and the aux. is closest to the driver since that is where the action is.

Edited January 24, 2009 by mackdaddy

[jaysm35a2]

Hate to bring up a ollllllld thread but I figure that ill add to this than make a new one. Im new to the duplex Mack also. It hurts the truck when empty to leave the right in high and just shift it like a 5 speed? Im a litte lost and I dont want to hurt the B I have. -Jay

[HK Trucking]

http://www.bigmacktrucks.com/index.php?showtopic=13481

[jaysm35a2]

Im going to go with its ok empty. - J

Also , you shift around 12 right?

Edited May 2, 2010 by jaysm35a2

[HK Trucking]

Im going to go with its ok empty. - J

Also , you shift around 12 right?

If your truck still has the original Thermodyne diesel, then the operating range is 1500 to 2100 RPM, anything below 1500 is "lugging", and you'll eventually burn a hole in a piston or blow a head gasket if you lug those engines.

That's the reason for the extra gears on the compound - to allow the engine to stay in the correct operating range when pulling.

.

[jaysm35a2]

Yes it has the orginal engine. Am I shifting too low at 1200 RPM? I was told that was what it shifted at. I havent drivin it much. Im going to learn the correct way to shift it before I do much more. I know you go : 1 low 1 high 2 low 2 high and so on from what I read. Seems like everyone has there own way of driving. I read that stay in high and shift like a 5 speed when empty and dont lug under 1500 PRM while driving your ok also. Thanks for talking with me on this. -

[HK Trucking]

If you're using the tach to upshift the main, then yes, if you run the engine up to 2100 you'll catch the next gear on the main at about 1200. If the engine will accelerate from 1200 with no problem then that's not considered lugging. Lugging is when the engine is working with full throttle under 1500 RPM and will not increase RPM. Use the compound as necessary to prevent the engine from lugging.

[hillconst1]

Hi,

I have two trucks with duplex transmissions, one is a trd720, the other is a trd72. I will start with the trd720, this is simple, 5 speed box with low and direct rear box, this trans has 5 progressive ratios, with no overdrive, so it is shifted 1st, low then high, 2nd low then high, and so on, 10 gears... the other trans screws things up some, the front box has 5 progressive ratios BUT 4 th is direct and 5th is overdrive( also known as overgear) and has the some low and direct two speed box on the rear. This will give yo 10 gears right? well yes and no, 4th gear in direct is 1.0 to 1.0 ratio, ( input shaft turns 1 turn output 1 turn). now if you shift into 5th low the main box is in over drive( 0.69 to 1) but the low gear in the 2 speed box lowers the ratio, this will give you a ratio of 1.04 to 1 , almost the same a 4th direct, so you have no need to use this gear sence it is the same a 4th high and uses two gear reductions to get the same ratio as conecting the input shaft to the output shaft. So the the proper shift for the 9 speed overgear trans is the same as the 10 speed other than you omit the 5th low because it is a duplcate ratio. If thats not enough for you you can get into your trdx72 and trdx720 trans, these trans. have a very low gear in 1st. for heavy work, this realy misses up things, this trans you have to shift very differently than the other two. All 4 of these transmissions are duplex transmissions. So I would say that all of you are correct. I believe that is why all of these trucks have those little tags up by the sun visor, there are so many variations, it just comes down to what your truck was designed to do, and if the guy that ordered the truck knew what he was doing. Fred

p.s. the triplex and the quadraplex have some duplicate ratios also because of the overgear 5 speed front box and overdrive in the rear box.

You are exactly right, a quad is not a quad. Not all quads used the same sequence hence 14spd, 18spd, 20spd. You have to know your ratio list before you can figure out what you can use and what you can't. I bought a '60 B613 witha 20spd when I was 18 yrs old and had it down in no time. Once you get the feel it sure is a lot of fun!

[HK Trucking]

You are exactly right, a quad is not a quad. Not all quads used the same sequence hence 14spd, 18spd, 20spd. You have to know your ratio list before you can figure out what you can use and what you can't. I bought a '60 B613 witha 20spd when I was 18 yrs old and had it down in no time. Once you get the feel it sure is a lot of fun!

The "20 speed" would be thr TRQ720, those had more overdrive on 5th, so you could actually use all 3 splits in 5th if you wanted to.

I've seen the TRQ7210 referred to as the 14 speed quad box, but I owned one of those in a 1962 B613T, and drove one in a B61SX, and they shift the exact same way as the TRQ7220, which is known as the 18 speed quad box.

The TRQ7210 and the TRQ7220 have some miniscule differences in various ratios, but I could never tell the difference when shifting one or the other.

.

[other dog]

If you're using the tach to upshift the main, then yes, if you run the engine up to 2100 you'll catch the next gear on the main at about 1200. If the engine will accelerate from 1200 with no problem then that's not considered lugging. Lugging is when the engine is working with full throttle under 1500 RPM and will not increase RPM. Use the compound as necessary to prevent the engine from lugging.

I started reading this and thought "gee,this sounds familiar"...didn't realize the original post was that old. But I would imagine that if you're not used to older equipment it's hard to imagine nowadays. The newer engines are so different. Lugging the engine was just something you never did, you had to keep 'em "wound up"-now they're all about like a maxidyne, you can pull down to 11-1200 rpms and it won't hurt them. That's what they say anyway, I still downshift at about 14-1500. And it used to be if you let the temp. get much over 200 too much, you'd cooked an engine. Now the fan doesn't even come on until it gets to 205 degrees.

[fundadtn]

I have never had the oppertunity to drive a twin stick mack transmission and I was wondering how they are setup. For example I have herd that the basic setup is a 5 or 6 speed main and a hi-lo-reverse secondary. Is the hi-lo ment to split the gears? Also is there any online info on the different mack twin sticks and diagrams/pictures/instruction on the shift patterns? How does one shift progressivly through the gears?

I saw one mack on ebay that had a real weird shift pattern that loked like an incomplete H shift pattern like this :

gear - gear - gear

xxxx- gear - xxxx

(it was one of the two shift patterns and you could not really see the other pattern for the second stick)

Thanks!

There were several types of "TWO STICK" transmissions. After the Maxidyne engine came out, with the 5 speed transmission, Mack also made what was known as an extended range transmission, that did have 2 gear shifts, but is not anywhere near the same as the old original 2 stick transmissions. The Duplex was essentially a 10 speed tranny with a 5 speed main box, and a 2 speed auxilliary. For each gear on the main box, you split it with the auxilliary transmission. So each MB, gear was divided into 2 steps. The triplex had a 3 speed auxilliary, and a quadraplex had a 4 speed auxilliary. With the Quadraplex, when you upshifted the main, you brought the aux immediately back to 2nd, if you brought it back to low/1st then your speed ratio was the same as the previous MB gear in high on the aux. THIS CAME IN HANDY WHEN YOU WERE PULLING A HEAVY LOAD UP A HILL FROM A START AT THE BOTTOM.

For the "most part" unless you were really havily loaded, you started off in 2nd on the MB, and 1st on the Aux. You progressed through the aux to 4th, and then the next shift, you shifted to 3rd on the MB, and then brought the aux immediately back to 2nd. Then you upshifted to 3rd aux, and then 4th aux, and then the MB to 4th, and the aux back to 2nd. Down shifting was the opposite. If you were really havily loaded or in soft dirt, you started off in 1st MB, and 1st in the aux. (being really easy on the clutch to keep from throwing a U=joint, or wrinkling the drive line.) There are some videos on youtube if you want to see how the 2 stick was progressively shifted. I also created a visual video demonstrating how to shift a quadraplex. these types of transmission were primarily designed for the old gasoline and early thermodyne engines, with low torque factors. If you try to use one behind a maxidyne or later variant engines, it will take out the bearings in the trans... pretty quickly, and I have heard it will break the gears, so I wouldn't recommend using one with the high torque engines. I hope this helps you.

Dan.