One of these days I'm going to get around to buying an old Jeep truck and installing a Cummins. Most likely it will be a 4BT for space, weight, and torque considerations. My understanding is that most of the 6BT upgrades can be applied to the 4BT to make power.

The real question is this though: what transmission or geartrain to use? My first thought is to use an automatic to help keep the turbo spooled up for any hauling I might do. I would prefer to have a wide range of gears, like 5 or 6 speeds. My hauling needs right now are fairly light, but I prefer to be prepared, and really prefer to do this once. Also, the transmission needs to 4x4 compatible.

Can the newer electronic automatics be used with the older all mechanical 4Bt's (I'm really looking at either the 545RFE, the 68RE, or the GM 6L80E)? If not, would you guys suggest an auxiliary transmission like Gear Venders makes and mate that to a 3 or 4 speed? Should I skip that and just use an NV4500, NV5600, or ZF manual?

Open to all thoughts and suggestions.

 

You would get more action on Pavement Sucks ot Pirate 4X4 on ansews

 

Why not just use an Allison?

That's what the Utility truck Mfgs did. The little 4BT will kill more tranny than you think.

 

J, I'll look into pirate 4x4. Thanks.

Pat, I've never done a powertrain upgrade or swap before. I'm trying to keep the cost and complexity down and reliability up. Any idea on how to do the 4BT to Allison mating?

 

Either bolt up directly with a Chevy step van adapter with either stock adapter ( canted 11 degrees ) or the pricier solid billet adapter from PATC. If you want to go Industrial, I believe the later step vans that came with Allisons had SAE bellhousings.

Try over on 4btswaps.com for more involved info.