M934a1 Detroit Series 60 12.7L Swap

[Bullhead]

Looking into a motor swap for a possible purchase. Is there a reason i can not find any swaps for this motor into a 5 ton truck? Two motors i am looking at are the Detroit 12.7L or the n14, but want better mileage and decent power, has anyone put in the 12.7L with a 10/13/15 speed manual? Also my first post and this forum seems to be pretty good.

 

[simp5782]

Looking into a motor swap for a possible purchase. Is there a reason i can not find any swaps for this motor into a 5 ton truck? Two motors i am looking at are the Detroit 12.7L or the n14, but want better mileage and decent power, has anyone put in the 12.7L with a 10/13/15 speed manual? Also my first post and this forum seems to be pretty good.

60 series are happy around 1800. The 916A1s used a direct drive allison and a .98 od transfer case on 44in tall tires and they screamed down the highway. With 4.90 gears.

Basically with a double overdrive transmission equates to a triple overdrive setup with the T1138 transfer case on 14.00r20s would be around 70mph at 1600rpms. I dont think you would have the umph to keep in overdrive with a 934

 

[Bullhead]

The truck currently has 53 inch tires on it, 16s 20.00 I believe? Think an n14 525hp be better or the 12.7 DD with 470Hp, should be enough with either a 13/18 speed? Want good mileage but have the cruise rpm lower

 

[simp5782]

For what a 60 series cost. Plus that cost of a 15 or 18spd, plus a stronger transfer case, cause the t1138 won't stand up, and all the crap to make it work = alot

Cheaper solution. Sell your 934 but keep the box. Buy a 7 ton. Swap the oshkosh 30000 series transfer case to an oshkosh 55000 then. Install the box and be done.

 

[Lukes_deuce]

Ive never heard of anyone swapping in a 60 series. Probably because its computer controlled and no one wants to deal with that.

Big OTR motors have been put in 5 tons. Some guys have made the rest of the drive train last, some guys have blown up trans and transfer cases. It depends on your use. If its mainly over the road, I think you can be easy on it and be ok. If you plan on off roading the 934, I think the transfer case will be the weak link, especially in reverse, with a big motor in front of it.

 

[Bullhead]

The swap doesn’t scare me as I am an Industrial Electrician Welder. I want decent MPG but a common engine. A friend of mine who has ran and owned a 12.7 DD, M11, and n14. One of these power plants I would really like. Staying mechanical is always a good thing but the electronics of these do not scare me away. Each have their own pros and cons. The M11’s are interesting since they are lighter. But also the expandable box most likely will be removed later on with an aluminum body, that may or may not happen if the truck does well from an engine swap. I am just surprised I can not find any info as the motors do not cost much or to fix. I am not interested in another style truck.

 

[simp5782]

You won't get more than 7 or 8mpg period

 

[Nomadic]

For what a 60 series cost. Plus that cost of a 15 or 18spd, plus a stronger transfer case, cause the t1138 won't stand up, and all the crap to make it work = alot

Cheaper solution. Sell your 934 but keep the box. Buy a 7 ton. Swap the oshkosh 30000 series transfer case to an oshkosh 55000 then. Install the box and be done.

I'm curious about the Oshkosh 30000 transfer case in the 7-ton. Why do you suggest to swap it for a 55000?

 

[simp5782]

I'm curious about the Oshkosh 30000 transfer case in the 7-ton. Why do you suggest to swap it for a 55000?

Oshkosh 30000 is an underdrive 1.26 to 1 unit. Single speed

55000 is a .98 to 1 high so it has some overdrive. 2.77 to 1 low range

7 ton has a double overdrive allison. The oshkosh case would allow better rpm at cruising speed

 

[98G]

What's your definition of "decent mpg" ?

 

[Bullhead]

Decent i would say around 8 going 55-60 max.
Friend of mine has the same motor with Pittsburgh Power Pac on it at around 700 hp, this would be in a gravel truck and gets 10.5 Empty. Which is still lighter then the 934 that’s for sure, running a 15 over but of course the rpm would be lower. Really hard to say for this application but would be great to have rpm down as top speed not a concern.

Edit, the gravel truck weights 37000lbs empty so i guess its heavier and the rpm would be at 1400rpm

 

[Lukes_deuce]

Decent i would say around 8 going 55-60 max.
Friend of mine has the same motor with Pittsburgh Power Pac on it at around 700 hp, this would be in a gravel truck and gets 10.5 Empty. Which is still lighter then the 934 that’s for sure, running a 15 over but of course the rpm would be lower. Really hard to say for this application but would be great to have rpm down as top speed not a concern.

Edit, the gravel truck weights 37000lbs empty so i guess its heavier and the rpm would be at 1400rpm

You might be able to squeeze 8 mpg out of a M11 with the right OD ratio. These trucks do not have good gearing or any aerodynamics. My vote would be a mechanical M11 & 13 speed trans. They are 500 pounds lighter than an N14, much cheaper and can still put out plenty of power to move your 934 around. Its also a little smaller than the 250 in the truck now, so you have more space to work with when fitting in everything.