Im thinking about swapping out my old 350sb engine to cummins power. The truck is going to be my wheeler so i dont know which one would be better for power and weight distribution? I want to be able to mod either one to the 300-400hp range. The truck will at some point in time be running 37-38.5in tires with a 8-10in lift im not sure which one yet though. Any advice would be appreciated.

 

The 4BT is obviously the lighter and smaller choice, but the 6BT will likely be the cheaper and ultimately easier choice. The downside to a 4BT is availability and the amount of work it will need to make and maintain your power goal. The downside to the 6BT is size and weight which can make a short top heavy rig even more squirly. The downside to either of them, especially in an off road rig is torque and spooling; diesel torque can quickly destroy puny drivetrain turning big tires on off road conditions, and sometimes an improperly setup system will not produce the snappy throttle response you would get with a high horse gasser...not to mention a little lag and fuel loading followed by rapid boosting can break parts as well or put you somewhere you don't want to be (I've witnessed a compound turbo fire breathing 12 valve send a 2.5 ton Rockwell and Ag tire equipped Chevy sideways right into a tree when the chargers finally lit and it hooked). Just some things to consider...

When it comes down to it, all that matters if what you can find and what you can make of it. A donor 12 valve truck would be a pretty good start...

 

Thanks i think i was kind of leaning towards the 6bt anyways. There all over craiglist and i havnt found a 4bt yet, plus ive been researching how to mod them and the 6bt does seem alot cheaper and easier. Im going to definetly have to get used to the power but hopefully i wont be having any issues when wheeling haha im just going to be going straight in the mud no big turns hopefuly haha

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and what would be a good transmission to pair with the 6bt in a chev? The 700r4 is starting to go out on me.

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What would be not so exspensive tranny to drop in it aswell that would still hold up? The 700r4 in my truck is starting to go out on me and i want to replace it with one that could be used with the 12v aswell.

 

Easiest and cheapest is just to stick to whatever transmission is behind the Cummins. Toughest is generally thought to be the NV4500 5-speed in the 2nd Gen trucks. The trouble comes when running passenger side drop front drivetrain as 2nd Gen on Dodges had driver side drop and funny spline counts on the transmissions (assuming manual still). The automatics of the Dodge variety tend to have a fairly bad rap, but setup properly will do whatever you ask of them....for a price, especially when throwing around big power.

Find a good donor first and go from there. The 1st Gen Dodge trucks will be easy and will have the passenger side drop you want (and a D60/61 front, D70 rear and NP205 t-case for the 4x4 models). Just my $0.02..

 

6bt with nv4500! best set up i think.