My Sub is, currently, a lawn ornament. I changed direction mid course and will be selling the engine and trans; L31, 4L80E (core). I want to remove the computer and run a 12v 6BT. The question I put to you good people is which trans to run? I have a few choices, but am not sure which way to go; the only certainty is I would prefer to keep an automatic, as my knees may not be too happy with a clutch and traffic, along with the sourcing the needed conversion parts and the actual fitting into the truck, though a 4500 is not off the table. I do not want to spend a ton of cash (no more than a remanned 4L80) but it needs to be strong enough to handle the torque and up to a 12k loaded trailer. To support this I'm also converting to a dually using a boneyard axle.

I did recently find a 24v NV combo in my local yard, but it's being sold as a core; yard guys told me they think it ran but could not guarantee anything. Price is really good, though it's missing the turbo and a few assorted items (ebay has them dirt cheap) so that doesn't concern me. I don't enjoy the thought of swapping that VP44 out for a P pump, either, being an added expense (pump, front cover, lines, brackets, etc) but will have to do it to avoid the computer. A better option may be eBay; a seller in Ohio has several 12v Allison 545 combos for about the same price as getting that 24v converted and running. The only issue is with the 545. Need to do a bit more research on it and decide if it's viable.

Any other trans suggestions are greatly needed here.

 

I would go with the 6.5L Detroit Turbo Diesel. The 4L80 transmission will bolt right in to that as it was included in many of the diesel version Suburban 2500, or the 4L60 in the 1500.

I do have the 4L80 in my 1500 5.7, and it seems to do well.