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Matching Up An Older Mack Engine With An Allison Auto


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Hi,

Was wondering if anyone had success getting an older Mack engine to work with an Allison auto in a B or H model truck?

Wondering if there are proven combos of the two that are out there working in one of these older trucks.

If so, just curious what the engine / tranny model that worked and how much fabrication was needed to get it to happen!

Thanks!

Rob

p.s. Yes, I am considering making a "lazy man" model out of my H series. Love the look and want to restore to original appearance but might put a modern drive train under her to make it a real easy hauler for the family. This is just data gathering.

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A 237 & 5 $peed probably make$ more $en$e unle$$ you got lot$ of the$e!!!

Yup. The 5 sp. is certainly on the list of possibles (and a good one).

I am just seeing how far I might be able to take it... with the Allison being a possible consideration.

$$ is expected. However, at this point, I am not even sure what would work (especially using a Mack engine).

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Believe it or not,an automatic could be ordered in a B model,but if you ask me,that would be about like buying a case of empty beer cans.The main thing you gotta remember when considering a transmission swap such as an automatic or even going to a 5 speed,you're going to have to consider your rears too or you might end up with a 40 mph truck.

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Believe it or not,an automatic could be ordered in a B model,but if you ask me,that would be about like buying a case of empty beer cans.The main thing you gotta remember when considering a transmission swap such as an automatic or even going to a 5 speed,you're going to have to consider your rears too or you might end up with a 40 mph truck.

It appears switching to an Allison will be a major re-think of the engine / tranny / rears / mounting locations / etc.

The good news is, all options are still possible because the truck has not even been torn down yet.

Hopefully I will have a direction for the entire drive line in the next 3-4 weeks.

I would not attempt anything this ambitious on my own.

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Well, allow me to preface my remarks by stating that I have an innate dislike of automatic transmissions.

That said, there were lots of Mack fire trucks factory equipped with Mack diesel engines and Allison automatics.

The ones I remember sounded like they had either a 237 Maxidyne or a ENDT673C 250 H.P. thermodyne in them. Never actually popped the engine cover on one to see for sure. Maybe some of our fire truck friends on here can shed some light on this.

You stated earlier that your H model currently has a triplex, so as Superdog said earlier, you're gonna have to do some calculations of trans high gear ratios vs your rear axle ratio if considering a transmission swap. For example, if you have a TRT7220 triplex now and you replace it with a TRL107, 1076 or 1078 5 speed, the high gear in the 5 speed is 1:1, same ratio as your triplex has in 4th direct, therefore your truck would be very slow with the 5 speed unless you change the rear axle ratio to a faster one. This is just one example of what could happen, there are many variables depending on the particular transmission being considered for the swap. Just wanted to give a heads up, so you don't get any surprises, all things must be carefully considered & calculated.

"If You Can't Shift It Smoothly, You Shouldn't Be Driving It"

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