Can You Put An Allison Transmission On A Cummins?

Cummins engines are popular because of their reputation for reliability and undemanding maintenance and the availability of upgrades. Due to the robust design and plentitude of aftermarket parts, it's tempting to make improvements to an already-capable Cummins engine. A popular upgrade is to swap out the stock transmission for a different unit. This can make your truck more versatile and fuel-efficient or better suited for a particular purpose. Allison-branded transmissions can definitely be used with Cummins diesel engines, and Allison has even partnered with Cummins to produce transmissions for their low-emissions engines. 

Allison transmissions that fit with Cummins engines include the Allison 1000 series that comes behind many of GM's Duramax diesel-powered trucks. The 3000 series Allison automatic is found in sanitation, utility, and emergency vehicles and public buses. The Allison 4000 series is used for heavy-duty vehicles including buses, construction equipment, and military vehicles, while the TC 10 series is made for heavy-load carrying vehicles like tractor trailers. For pickup truck owners, an Allison transmission can be a big upgrade over the stock unit. Many Ram trucks come with Cummins engines and 68RFE six-speed units made by Chrysler, and the 68RFE's maximum torque capacity is 750 lb-ft. The six-speed Allison 1000 series transmission can handle up to 900 lb-ft. 

Allison Transmission used to be owned by General Motors and has produced components for aircraft and marine transmissions during wartime. Its maybe best known for the 1000 series transmission, which made its way into trucks from Ford, Chevrolet, and GMC. Vehicles that are equipped with the Allison 1000 series transmission include the Chevy Colorado, Hummer H1, and GMC Sierra. For owners of trucks with Cummins engines, fitting an Allison transmission is worth considering, given the somewhat straightforward swap process and potential gains.

The process for installing an Allison transmission to a Cummins engine begins by researching which Allison transmission unit is compatible with your particular vehicle. ATS Diesel sells complete conversion kits to enable a Cummins/Allison combination. These kits can cost more than $11,000, and you might still need to fabricate or purchase new engine or transmission mounts. Along with the new transmission and torque converter, you'll get the correct electrical components to ensure the Cummins engine and Allison transmission work properly together. This includes wiring harnesses, sensors, and control modules, as well as the hardware to securely mount them. These modules monitor and control how and when the transmission shifts.

Use case applicability is a key factor when combining a Cummins engine and Allison transmission, because there are countless combinations of the two. If you pull a heavy trailer or do a lot of off-roading, you'll want to make sure your transmission is geared for those uses. While relatively manageable, adapting a Cummins engine to use an Allison transmission will require substantial mechanical and electrical knowledge to safely and decently execute. 

You'll also need the right set of tools and equipment when working on an engine and transmission; an extra set of hands can be invaluable when it comes time to mate the two components. Even if you have experience with major mechanical projects, this is a complex job with a high probability of error or omission during the build. If you pay to have a professional drop an Allison transmission behind your Cummins diesel engine, you'll have a guarantee that the upgrade works as intended.