Cummins to Chevy Allison Adapters

This topic covers available adapters for bolting a 1000-2550 series Allison with the Chevy bellhousing to the Cummins B and ISB engines.

Currently the adapters for Chevy bellhousings are all quite similar in design, for space requirements they require a Ford 6.0 or 6.4 diesel starter, use a custom flexplate, and range in price from $1195 to over $1600 from many different vendors on the web, including ebay.   Some of these were designed for the 4L80E, and do not have the bolt holes on the bottom edge, and even though these would “work” for an Allison, it’s best to get the Allison version when you can.

The advantage of this adapter is it has the fewest parts and is relatively thin in design, compared to others out there. The flexplate is the thing I dislike most about this type of adapter, not all of the manufacturers balance them (might argue they don’t need balanced) and in my opinion do not have as much engineered flexibility as they should.   The other things about this adapter that can be a challenge is the transmission cooler ports are often close to the exhaust and the starter has to be relocated to the passenger, exhaust side of the engine as well (because that is where the accommodation for the starter is in the Chevy bellhousing).   In some trucks this is a really poor location for the starter so plan your best option and you will be glad you did.