Duramax Diesel Conversions

[More Power]

I received this email this morning, asking about an '80s square body conversion. Thought the discussion might be of value here.

On 2021-04-15:
> I am considering doing a Duramax/Allison swap in my 1984 chev c70
> rollback it currently has a 427 5 speed,
>
> In has a cable driven speedometer I wondering what you have done to
> correct that ?
>
> Also does the Allison have the required hardware internally to drive a
> PTO , I know it has a cover plate but what about the internal gear
> required to drive the PTO
>
> If I do proceed with this project I will be purchasing you guide. Do
> you need to buy a wiring harness to make the conversion or does the
> guide show you how to modify the existing harness.
>
> Thanks In Advance
>
> Larry
>
>

Hi Larry,

I recommend you modify the dash of your 1984 truck to accept the new instrument panel. This will solve the speedometer problem and you'll gain a lot of functionality with the new powertrain. I also recommend you install the steering column that matches your engine package. This'll make it easier to shift the Allison, and it'll add a lot of functionality as well.

I know the early Allisons were setup to run a Power Take-Off, but I know the PTO was dropped a few years into production... before re-adding PTO in more recent models. So, to answer you, I don't know. I guess it sort of depends on model year, but I don't have a model year breakdown for the PTO.

For wiring harnesses, I recommend using the OE harness that matches/came with your engine package. New, these factory harnesses are about $600/ea (one for the engine and one for the Allison). One of the more expensive options is to acquire an aftermarket stripped-down harness that was designed for boats/RVs/basic conversions, but they require a specially programmed ECM/TCM and you'll lose most/all of the luxury features that came with GM's 2500/3500 trucks. Contact ppepower.com or bankspower.com for more info about their harnesses and ECM/TCM. Just remember that using an OE harness doesn't force you to use the extra features - you can pick and choose. The Conversion Guide we offer shows you how to install the OE harnesses, which is the least expensive option - no cost if it came with your engine/trans.

In the meantime, I'd suggest you spend some time with the following article that shows a 1987 Chevy C30 conversion...

https://www.thedieselpage.com/featur...Conversion.htm

Good luck,

Jim