Too Much Torque?

[dockmen027]

A friend has a B-75 twin-screw in which he put a 300 Maxidyne in, and still uses the origional triplex. Someone told him that is too much torque for that transmission, is that true?

[Rob]

A friend has a B-75 twin-screw in which he put a 300 Maxidyne in, and still uses the origional triplex. Someone told him that is too much torque for that transmission, is that true?

If the truck is driven responsibly and the driver is not "hot of the throttle", it will last just fine. The torque rise of that engine is rated much higher than the design criteria of the transmission but it has been dozens of time in the past. The key to make it live is to gradually apply power when loaded.

The only real drawback that I experienced with mine was that the engine was hardly ever in it's torque band for maximum efficiency the engine was designed for. This is not detrimental to operation at all.

Rob

[HK Trucking]

If the truck is driven responsibly and the driver is not "hot of the throttle", it will last just fine. The torque rise of that engine is rated much higher than the design criteria of the transmission but it has been dozens of time in the past. The key to make it live is to gradually apply power when loaded.

The only real drawback that I experienced with mine was that the engine was hardly ever in it's torque band for maximum efficiency the engine was designed for. This is not detrimental to operation at all.

Rob

That's the key:

Drive the truck the way it would be driven if it still had a Thermodyne in it - shift as needed to keep the engine between 1500 to 2100 RPM's, don't pull that Maxidyne down into it's high torque band which is 1200 - 1300 RPM.

[theakerstwo]

That's the key:

Drive the truck the way it would be driven if it still had a Thermodyne in it - shift as needed to keep the engine between 1500 to 2100 RPM's, don't pull that Maxidyne down into it's high torque band which is 1200 - 1300 RPM.

And if you want to get the pump set up better then send in and have the governor set up for a ten speed trans and that will let the bottom end torque be raised up to the top of the rpm range and it will feel better to drive. The maxidyne pump makes good torqe at the bottom but then with a ten speed it gets to feel like a sled as it gets close to 2100 rpm. Now with it set for a ten speed the power builds as the rpm does and just feels like you want it to.

[Rob]

The maxidyne pump makes good torqe at the bottom but then with a ten speed it gets to feel like a sled as it gets close to 2100 rpm. Now with it set for a ten speed the power builds as the rpm does and just feels like you want it to.

That is a real good analogy Glenn. I had an ENDT676, (283hp) in a B model with a triplex and the power really fell off above 1600 rpm. It actually felt as if the engine was starving for fuel but was not. For the power band of the engine, you ran out of gear much too fast.

Rob

[rw613]

That is a real good analogy Glenn. I had an ENDT676, (283hp) in a B model with a triplex and the power really fell off above 1600 rpm. It actually felt as if the engine was starving for fuel but was not. For the power band of the engine, you ran out of gear much too fast.

Rob

it will take it we have a f model with a 375 v8 with a triplex with a million 8hundred thousand on it

[dockmen027]

Having only driven an occasional CH since 1980 (prior to that mostly 237's and 300's), I lost track of the later Mack engine models. In the 80's they came out with the 300 plus which was used with a 9 spd or more, is that a 300 with a different pump? Also, before my arrival at ABF they had 1987-88 R-models that said Econodyne on the hood, was that a 300 plus?

Thanks,

John

[Rob]

Having only driven an occasional CH since 1980 (prior to that mostly 237's and 300's), I lost track of the later Mack engine models. In the 80's they came out with the 300 plus which was used with a 9 spd or more, is that a 300 with a different pump? Also, before my arrival at ABF they had 1987-88 R-models that said Econodyne on the hood, was that a 300 plus?

Thanks,

John

It very well could have been. The econodyne engines were the same basically as the Maxidyne series with different pump/governor calibrations. All of the Maxidyne engines that I've seen were backed by either a five, or six speed transmission to take advantage of the torque rise of that series.

Rob

[Rob]

it will take it we have a f model with a 375 v8 with a triplex with a million 8hundred thousand on it

Yes they will take it if not rammed upon. It has been years since I've seen a single countershaft transmission worked regularly but in the past it was commonplace with the horsepower race of the 70's. I've seen several more twisted and broken input shafts on triplexs, and quadraplex transmissions than I've seen good ones when a Maxidyne engine was placed up front and the truck worked as designed. This is vocational work I'm referring to.

Glad to hear you have a good one. Most likely it has had a pick of easy drivers. If it does break nowadays, it will be expensive if not cost prohibitive to repair.

Rob

[Mark from OZ]

I think the Quad duplex ect was rated at 700f/lbs touque or there about

I have seen some bigger engines in front of the older boxes some lasted

most eventualy died. I have seen a quad box with a fuelled up 237 but it was owner driven

it lasted fair few years. But when it went bang every thing inside the box was totally wore out..............

[HK Trucking]

In addition to my earlier comments, I should add that in the past I have transplanted a 237 and a 285 into trucks with quad boxes and it worked well, no trans troubles.

But just like anything else, if you drive it sensibly and shift it smoothly it will last a long time.

Drive it rough & crazy and the transmission will be scrap iron in short order.

[other dog]

In addition to my earlier comments, I should add that in the past I have transplanted a 237 and a 285 into trucks with quad boxes and it worked well, no trans troubles.

But just like anything else, if you drive it sensibly and shift it smoothly it will last a long time.

Drive it rough & crazy and the transmission will be scrap iron in short order.

that's it in a nutshell- it's all in how you drive it and what it's going to be used for.

[alphadog]

that's it in a nutshell- it's all in how you drive it.

As for me, I would match the drivetrain with margin and durability in mind. If the engine has 1000 lbs torque, I would want a transmission that has 1200 lbs+ rating. I personaly am more agressive with the truck sort of the way I drove 21/2 &5 ton military trucks. Not abusive mind you, but I don't baby them either.Thats my 2 cents.