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Thread: M1008 12 Valve Cummins Swap

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    Default M1008 12 Valve Cummins Swap

    Recently started a 12 valve Cummins swap on my 1986 M1008 ex-fire truck. Thought I would start a build thread.

    Won the truck on auction. 93,000 miles. Original plan was to sell but the history of the truck was too neat to pass up.
    End goal of the project is to have an all around solid truck that can tow, haul, daily drive, and weekend wheel. Not perfect at one thing but good at many.


    Truck after it was delivered. Washed and waxed of course.
    20180916_152016.jpg20180916_152305.jpg20180916_152404.jpg20180916_152150.jpg
    Rust isn't terrible. Oddly enough the heavy rust is only on the drivers side of the frame, axle, and suspension components.


    Truck has progressed much further. I'll post more once I get the pictures sorted out.

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    Colonel Glockfan's Avatar
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    Looking forward to seeing this...

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    I'd recommend planning it out well. I saw one of these conversions that left a lot to be desired, sitting at too much of an angle, fractions of an inch from the firewall, extremely loud and rattly. The guy who owns it wishes he left it stock.

    That said, I'm sure it could be done better, and look forward to seeing your progress.

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    4 Star General 91W350's Avatar
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    If you have not bought your Cummins yet, look for 4BT. They are two cylinders shorter and will be much easier to set in the hole. With 4.56 ears, you will still have torque to burn.
    The five tons have dried up and are about gone, we have some deuce remains around, the military salvage yard is looking pretty empty these days!

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    Thanks all for the words of advice. I've been planning this project for about 10 years and just recently ran across all the parts needed and for cheap. Original idea was to keep this project cheap too but we all know how that works.

    Order of purchase
    1994 Ram 3500 NV4500
    1995 Cummins 12 valve with 185,000 miles
    4.10 K30 axle set (dana 60, 14 bolt)
    1993 Ram NP205 with Getrag/nv4500 adapter
    Truck was last to purchase



    Here are the axles. A little rough but they were cheap and I could work with them.
    20180917_181351.jpg

    Started off last fall sand blasting the rear axle.
    20181104_131434.jpg

    Debated between welding the axles tubes or adding a truss/bridge. Truss was on sale so I picked it up and had a buddy burn it in.
    20181124_154208.jpg

    Adding the truss was really what changed the project direction.
    20181124_154224.jpg

    Poor quality shot of the painted axle before the pinion guard was bolted on. Used POR-15 base and semi gloss topcoat.
    20181217_164256.jpg

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    Sergeant Major 1StumpJumper's Avatar
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    The 4BT is great, but the shake, rattle, & roll? No thanks. 4.56 gears w/a TH400? No thanks. I have a 4BT, 6Bt, 4L80E, NV4500, and still would not use the 4BT in my M1008.
    M274A2
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    I have three friends that run around town in 73-87's that have a 6bt cummins swap. It is a great combo, does take some fabrication to get the crossmembers somewhere out of the way, cooling system up to snuff and the charge air cooler plumbed in. Fantastic torque, two of the guys I know are actually running the dodge Dana 61 axles with the numerically low gears just because they run stock sized tires and wanted to retain the excellent milage and highway low RPMs. With 4.10 or 4.56 gears, even with overdrive I'd want to run 37" or taller tires.

    Maybe someday I'll do the same swap. For now I just rattle around with 140 horsepower. Keep us updated!

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    The nice thing about this swap is the amount of knowledge and swap specific parts available just for 73-87 Chevy trucks.


    Found a better picture of the axle with truss/bridge and brakes installed. Added a 3/8" think diff cover as well.

    20190113_150600.jpg


    Bed removal was easy with the military cargo hooks inside the bed.

    20181222_092514.jpg

    Frame had rust but nothing horrible.

    20181222_100934-edit.jpg

    Too cold out to sand blast so I wire wheeled the rust off.

    20181223_124757.jpg

    Didn't turn out too bad.

    20181223_124803.jpg

    Prepped with POR-15 products before applying their base coat and top coat semi gloss black.

    20190114_165754.jpg

    Looks much better with frame and axle painted.

    20190114_165804.jpg


    Rear spring mounts will be swapped out for Offroad Design shackle flip and more flexible spring.

    20190114_172049.jpg


    Front half of the frame will be painted once I remove the engine. Currently waiting for a buyer before pulling the 6.2L. It's a good running engine and I want to make sure they can hear it run.

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    Corporal Matt S's Avatar
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    Quote Originally Posted by RedM1008Fire View Post
    Prepped with POR-15 products before applying their base coat and top coat semi gloss black.
    I'm about to do something similar with my M1031. I've used POR-15 in the past but the results weren't what as consistent as I would like. I was thinking of going with frame saver instead. Why did you choose POR-15 for your truck?
    1986 M1031

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    Quote Originally Posted by Matt S View Post
    I'm about to do something similar with my M1031. I've used POR-15 in the past but the results weren't what as consistent as I would like. I was thinking of going with frame saver instead. Why did you choose POR-15 for your truck?
    I've been using POR-15 for years and haven't had any issues with it but I find the key is the prep work. I always sand blast or wire wheel to remove rust, use POR degreaser, and finish up with POR metal prep. I think the metal prep is the most important part of the process. Also waiting for the proper time between coats which can be upwards of 6 hours.


    However, friends of mine have used chassis saver without problems. The end result turns out just as good so you should be fine using it. I don't know that brands whole process but definitely make sure you prep well.

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