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m818 trans swap??

Mullaney

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I searched around didn't find anything and I was wondering if I could fit a 9 or 10 speed eaton or similar in my m818 with the 250 nhc?

Any help would be appreciated.
.
It is an old thread, but here is a little information about @Crf450x and his installation of an Eaton RTO 9513 in a M923

 
Last edited:

fasttruck

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You will have to adapt the air controls on the transmission cover that sync the transmission and the transfer case together as to direction of travel to use a none stock transmission in a M809 series truck. Also measure length of intended transmission to see if it will fit between the engine and the transfer case. Another issue will be the clutch. The Army used a single disc clutch most roadrangers are expected to be use with a double disc clutch which could lead the input shaft problems.
 

Brutacus

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M818's have a short wheel base which limits the amount of space you have. Be sure to look at the width and length of the transmission, and how close the forward drive shaft is to the transmission. The M939's have the wider automatic transmission which use an offset carrier bearing to locate the drive shaft clear of the transmission. You would also have to relocate the transfercase rearward to accommodate the length of the 9 or 10 speed eaton. That runs into the issue of shortening the drive shaft. The rear drive shaft and u-joints can reach some extreme angles when the rear axles are at their max articulations. A shorter drive shaft, might not be able to accommodate the same angles as the longer drive shaft can. There are some old threads about this for m818's, and the eaton medium duty 6 speed transmissions have been brought up.
 

MyothersanM1

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I put in a Spicer ESO66-7B 7 (6+1) speed. It's a big well-involved project and the transmission is over 7 inches longer than the OEM 5-speed. However, the truck is much more drivable. No more 3rd to 4th gear "hole" and a better OD. I've been meaning to post it, but the write up is a mile long with a load of pictures.
Modifications and/or things to consider:

  1. Transfer case moved back (also requires spare tire/toolbox rack to be shimmed up)
  2. Midships driveshaft shortened, front lengthened
  3. Modified jackshaft
  4. Sprag actuation reengineered
  5. Modified throw out bearing
  6. Modification to forward cab tunnel to accommodate shift tower
  7. New compatible PTO and modified driveshaft if winch equipped (This is the only step I have not fully completed. I am waiting on my new driveshaft to be done at the shop)
Fresh rebuild right off the pallet
IMG_7907.jpg
 

Brutacus

Active member
Steel Soldiers Supporter
236
181
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Location
Marion, AR.
I put in a Spicer ESO66-7B 7 (6+1) speed. It's a big well-involved project and the transmission is over 7 inches longer than the OEM 5-speed. However, the truck is much more drivable. No more 3rd to 4th gear "hole" and a better OD. I've been meaning to post it, but the write up is a mile long with a load of pictures.
Modifications and/or things to consider:

  1. Transfer case moved back (also requires spare tire/toolbox rack to be shimmed up)
  2. Midships driveshaft shortened, front lengthened
  3. Modified jackshaft
  4. Sprag actuation reengineered
  5. Modified throw out bearing
  6. Modification to forward cab tunnel to accommodate shift tower
  7. New compatible PTO and modified driveshaft if winch equipped (This is the only step I have not fully completed. I am waiting on my new driveshaft to be done at the shop)
Fresh rebuild right off the pallet
View attachment 871176
I'm very interested in this transmission swap write up. How soon?
 

MyothersanM1

19K M1 Armor Crewman
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Culver City, CA
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