Transmission help

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Jan 15, 2026 | 06:24 AM

cooperkoh

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Transmission help

I know i have a few posts going. I am trying to get all my info so i know what to look out for. I am swapping a 12 valve into my 86 f350 cclb dually. I wanted a manual but after looking into it, it would be far too expensive for what i want. I am wondering what trans i should use, the motor is stock now but i plan to make more horsepower in the future. I dont want anything with expensive electronic controls or anything that would be expensive to adapt to the 12 valve. Right now i believe it has 3:55 gears.

Jan 15, 2026 | 07:25 AM

FuzzFace2

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Joined: Nov 2015

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From: Angier, NC

When you start down the path of fitting motors / transmissions / frames into something that never came with them and in your case cross breeding it will not be cheap unless you have everything already.

Part of the problem is that 6BT motor makes a lot of TQ and it was even known to hurt the transmission that the factory put behind it when it first came out, weak input shafts IIRC.
So even if the cost is high for the transmission that bolts to the motor in my book you are best to go with it.
If you find a different transmission that can handle the TQ you then have to spend money on adapter kits to get the 2 to bolt together then deal with flywheel / clutch parts and starters.
So in the long run what did you save money wise?
Just spend the money on the motor / transmission combo and only worry how to mount them in the frame you go with.
Again a full truck with the parts needed is the way to go.
Dave ----

Jan 15, 2026 | 07:34 AM

Olds64

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Joined: Jun 2017

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From: Edmond, OK

^^^THIS^^^

What engine/transmission does your truck have in it now? You know that

put an International diesel in the Bullnose trucks, right?

Jan 15, 2026 | 08:48 AM

cooperkoh

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Quote:

Originally Posted by FuzzFace2

i know i need to do it right the first time. i’m okay with spending money on an auto, i was just saying how i wanted a g56, nv5600 or a zf6 and they all were like 5k used, when i looked into autos they were all way cheaper, not to mention for most of those manuals id have to buy kits to make them work. I didn’t know what auto was best recommended that already mounts to a 12v.

Jan 15, 2026 | 08:52 AM

cooperkoh

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Quote:

Originally Posted by Olds64

^^^THIS^^^

What engine/transmission does your truck have in it now? You know that

put an International diesel in the Bullnose trucks, right?

I have an auto 6.9, i’m not interested in building up that, for this truck atleast. Turbo kits are expensive. i love how bullnoses look, i hate how 2nd gen dodges look and 1st gen’s are stupid expensive for a crew cab long bed. I really like 12 valves too, best of both worlds. i looked for turbo stuff for a while and with the cost of the turbos and injectors and upgrading all that goes with it, it wasn’t worth it to me. i got my 12 valve with 100k miles for 1700 complete and injectors.

Last edited by cooperkoh; Jan 15, 2026 at 08:54 AM.

Jan 15, 2026 | 05:24 PM

Franklin2

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Joined: Jan 2001

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From: Virginia

I would think the easiest transmission to use is one already made to mount to the cummins engine. As to which on is best, I would ask that question on a dodge diesel forum, I and most of these guys know nothing about dodge setups.