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M1028 tranny options with a 5.9L Cummins

Discussion in '1982-Present GM Diesel' started by kennyw, Jan 1, 2006.

  1. kennyw

    kennyw N9PHW Premium Member

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    I am starting to plan how I will put together my M1028 with the 1990 5.9L Cummins.

    Truck is geared low and limited to small tires though. 4.56 gears with 235/85R16 tires. I know it will need an overdrive, possibly an OD tranny plus a gear vendors OD to hit highway speeds with a Cummins. Anyone know what the optimum RPM on the highway is for the 5.9L?

    I'd love to put in a newer 6 spd but just need to find a good deal on one... what are my other options?

    12-30-2005 006.jpg

    11-26-2005 001.jpg
     
  2. camiswelding

    camiswelding 1/2 ton status

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    kenny,,, you know Ive looked at this in all the ways using an auto

    An efficient way is to go dodge 205 with one of the later od trannies ... thats what Ive been looking at seriously,,, but the time you put the bucks into the ranger or gear vendor you could have a built auto od
    crewcab59 just posted in the cummins conversion thread hes working on some projects that address tranny stuff,,, see his post
    I can probalby do a one off prototype now that my friend has a full machine shop up and working,,, but I need to get ahold a ctd first
    (new guns for trades!!!!)

    wouldnt an allison be cool
     
  3. CrewCab59

    CrewCab59 1/2 ton status

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    Cummins with auto trans.

    The Allison 1000 will bolt up ,5/6 speed as well.I 'm working on this stuff as we speek .
    The other trans is GM 4l80e ,Dodge 47rh.

    We just got installing a 12 valve and built up Dodge 47rh in a 96 Chevy 1/2 sub 4x4 with ifs,I trans works great but alot of fab work ( linkage,converter lock-up,misc stuff).

    The only way 4:56 gears are going to work is change to large tires.Plus your going have to change gov springs.Also it depends on if your going to drive on the interstate.

    My truck has 4:10 with 35's and are to much of a gear,3.73 would be better.


    Thanks
    CrewCab59
     
  4. imiceman44

    imiceman44 1 ton status

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    If anyone is goint that route (dodge 205) I have one available.
    :D
     
  5. kennyw

    kennyw N9PHW Premium Member

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    I'm kinda thinking the 4.56 axles are going to find their way into my K5 at some point... Then pickup another pair of dually axles with 3.73 gears instead. Would be cheaper than a Gear Vendor unit actually.

    I'm not wanting bigger tires for a couple reasons, first its a dually and would be difficult to run wider tires and second it is going to be a dedicated tow rig that runs mainly on the highway with a few miles off the road getting to and from the trail mainly. I will set the truck up to use as a recovery vehicle... but for the most part it should only need to be able to reach the trail head
     
  6. kennyw

    kennyw N9PHW Premium Member

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    It's been a little worked over by someone... lights up like a christmas tree at night now :doah: But I'll fix it back up and put the right grill guard and bumpers back on it. Paint it olive drab again. M1028 is a dually version of the M1008... at least the dually is one of the configurations that had that designation.

    My truck is rattle can forest green... someone put different doors on it with power windows and locks. I'm guessing the truck was purchased partially stripped and reassembled with civilian truck parts. Then given a rattle can paint job to make it all match. It also had a second fuel door installed in the rear of the bed with a suburban fuel tank though... interesting addition, but lost the tank going down the road because they did a half ass job of installing it.

    Oh... notice the grill? Kinda looks outa place right? It is a 79-80 grill in a 84 nose :doah:
     
  7. camiswelding

    camiswelding 1/2 ton status

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    kenny.. Im trying to get as deal closed on a cummins right now...thenIll be in this same conversion game as you for my crewcab.... but I had some ideas for you that Im sure youve thought about,,,

    how about a divorced transfer case and a 205 or one of the military ones out there,,,some of those are even air shift or electric shift,,which would do away with linkage hassles,,, and then you could use a 2x tranny with a shorty shaft,,,there should be enough length in a lwb,,especailly in a crew to be feasible,,, its another option Ive been looking at,,,

    Im real interested in what cc59 is doing
     
  8. diesel4me

    diesel4me 1 ton status Premium Member

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    modulator ??..

    I've seen cable operated vacuum modulators for race cars with superchargers..they can be used on diesels too,instead of a manual valve body.....but they cost about 120 bucks..I think TCI makes one,I saw them on a google search when I was looking for a vacuum switch for my 82 K20 that controls the vacuum to the modulator on my TH400..(it broke,and GM no longer sells one..:mad: )..

    I ended up putting the vacuum modulator hose directly to the vacuum pump,and turned the adjusting screw all the way in on the modulator..seems to shift fine,a bit soft and early..but my local tranny guy says he's done it that way for years,and it wont harm anything..hope he's right!..been 2 years that way,no problems yet,and I plow a lot with it..:crazy:
     
  9. ZZ4x4

    ZZ4x4 1/2 ton status

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    Actually, the M1028 is designated as a "shelter carrier". It doesn't mean dually. The M1028 and M1008 are the same except for extra wiring for power and communications to the bed ( circuit breaker on the right side of the dash), sometimes plumbing for engine driven AC , tie down brackets, a trac loc front D60 and NP205 xfer case. I seem to recall that an "A1" designation at the end would indicate dually (ie M1028A1)

    Oh, to answer your RPM question, it is best to keep the diesel RPMs below 2000rpm for the best fuel economy on the highway. If it were me, I'd gear to keep it at 2000rpm at about 70 mph.
     
  10. rjfguitar

    rjfguitar 3/4 ton status GMOTM Winner

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    You want to aim for 1,750-1,950RPM's at 70MPH. This basically takes a 3.54 ratio with a standard geared OD transmission, auto or manual an a 245-265 tire (obviously this could be changed with bigger tires but that range has the best selection of HD tires and what comes stock). This allows the best mileage when empty and just enough to chug along in OD with a modest load, and not redline the motor when in direct drive pulling hills and/or really loaded down. The higher ratio actually helps acceleration in town too, the cummins likes the higher ratio and spools up better.

    You can get a stand alone computer for a later 47RH tranny, and maybe even the 47RE but I think my 47RE's computer programming runs through the main truck computer, not a stand alone on later models, but I'm not positive on that.

    If you want a manual than hunt for an NV4500 5spd or the more expensive and harder to find NV5600 6 spd.
     
  11. imiceman44

    imiceman44 1 ton status

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    So you dropping the idea?
    Selling your 5.9 CTD?
     
  12. kennyw

    kennyw N9PHW Premium Member

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    Not completely dropped... just have a few other priorities right now that have to go before this project.
     
  13. camiswelding

    camiswelding 1/2 ton status

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    hey kenny.. Ive joined the cummins club... got mine yesterday,,, now I want to build it...
    time for tips everyone!!!
     

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