Why Should You Allison Swap Your Cummins Truck


Over the years we’ve seen many transmission and engine combinations, certain ones are better for driving, others for towing, racing, and so on. Take for example the Dodge 47/48 Re, the quick shifting nature is best suited for drag racing, but if you’re looking to tow a trailer at a high horsepower, this may not be the best transmission.

What would be a good transmission for a person that tows and wants a high horsepower? The Allison 1000 is a great option, which now isn’t just limited to the Duramax pickup trucks. The overall size of the internals of this transmission makes it a workhorse while maintaining longevity.

Double Down diesel's first Allison swapped truck is not a deicated puller.

These two factors are what drove Double Down diesel to put an Allison in a 2001 Cummins with a five-speed stick. They were never happy with the transmission that came in the Cummins. After years of breaking and rebuilding them, they wanted something that could handle the torque of the Cummins engine.

That is when they decided to convert to an Allison 1000 five-speed automatic. Looking back eight years ago, this was new territory as there weren’t any trucks out that had undergone this type of conversion.


One of the biggest benefits of the Allison is that you can get the shifts tweaked to the timing you want and it also learns your driving style. After tweaking the timing and tuning, the 2001 Cummins, with the Allison, could now handle 700-800 horsepower and was great on road, towing, and sled pulling.

Today this truck is a dedicated sled puller in the 2.6/3.0 smooth bore class, with the same transmission that was put in eight years ago. The Allison 1000 has proven its reliability and power year after year, even at the 1,150 horsepower mark.

The last thing you want to find in your transmission is a clutch pack like this. This pack was out of a Cummins transmission before the Allison swap.

Over the last eight years, the conversion technology has changed to become even more efficient and the Allison five-speed has replaced the six-speed, which means a double overdrive at a .61:1 ratio. The adaptability of the Allison makes it a great conversion choice, from the way it bolts to the engine, to learning how you personally drive.

For guys with a Dodge six-speed 68RFE transmission, the Allison is a great choice. To build a 68RFE to handle what the Allison can, you can expect to pay just as much as simply putting an Allison in.


For those wondering about the tap shifting capabilities, you don’t lose them. For the 6.7-liter Cummins, you can use the factory shifter, for older trucks you can purchase a new shifter, which can be installed in a matter of minutes and still has all factory functionality.

Overall the Allison can handle more power, with more functionality and longevity than other transmissions. An Allison swap a solid choice whether you want it for your daily driver, tow a lot or want to take your truck down the sled pulling track.

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