what has to be done to swap a c3116 to a c3126

[DeMilitarized]

This right here. It's simply not worth it unless you've got plenty of free time and know how. If your truck has a WTECII transmission it may not be natively-programmable to handle a 3126 as the A1 trucks rolled out the door with WTECIII systems in place. It's a generational thing you'll be pioneering on your own. The cab harness, PDP board, and some of the dash instrumentation are different. You may as well sell the 1078 you have and buy a M1078A1. If you want a clean A1 with a bad engine there's one on facebook for $7500.

Weld the block and run it. I would if I didn't already just buy one.

 

[adaptivehumanity]

After all the advice, I pulled and rebuilding the 3116, it does have a WTECIII but not worth the time in wiring. I will keep an eye on the auction's to find a 3126 that's blown up and swap a new motor into it. I almost bought a 09 M1083 with a C7 that was a fire loss, but the wife slapped me before I hit bid LOL.

 

[spoonbender]

I swapped out the CAT 3116 for a 2006 CAT C7 330HP on my LMTV A0.

The physical installation was relatively easy. However, all the wiring was relatively complicated.

With the C7, the A0 drives very very nice and the fuel consumption is also lower.

If you have any special questions then feel free to ask

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Hey- I have a A0 with a C7 in it that is not running, and trying to figure out all the wiriing (ugh!). I have a post in the FMTV thread - no sure if you'll see this anytime soon, but would most appreciate some guidance!

C7 engine (new swap)
original tranmission (3070)
have 3 different TCUs - 3700sp, and 2 3070PT ones
have current wiring harnesses (the plastic boxes)
new dash - and WTEC IV selector (to match TCU I guess?)

Thanks!

 

[coachgeo]

Hey- I have a A0 with a C7 in it that is not running, and trying to figure out all the wiriing (ugh!). I have a post in the FMTV thread - no sure if you'll see this anytime soon, but would most appreciate some guidance!

C7 engine (new swap)
original tranmission (3070)
have 3 different TCUs - 3700sp, and 2 3070PT ones
have current wiring harnesses (the plastic boxes)
new dash - and WTEC IV selector (to match TCU I guess?)

Thanks!

if does not reply real soon.... might work better to DM him

 

[GeneralDisorder]

Hey- I have a A0 with a C7 in it that is not running, and trying to figure out all the wiriing (ugh!). I have a post in the FMTV thread - no sure if you'll see this anytime soon, but would most appreciate some guidance!

C7 engine (new swap)
original tranmission (3070)
have 3 different TCUs - 3700sp, and 2 3070PT ones
have current wiring harnesses (the plastic boxes)
new dash - and WTEC IV selector (to match TCU I guess?)

Thanks!

I would love to check out WI and scout for property there. Probably not in the cards for me in the near future but some day.....

Can you read schematics?

 

[spoonbender]

I would love to check out WI and scout for property there. Probably not in the cards for me in the near future but some day.....

Can you read schematics?

Can kind of - I know there's a method to the schematics - have to lookup a quick tutorial. More interested in any lines that had to be added/customized (as you referred to in the other thread). The J1939 is terminated properly, but have to check the j1587, as seems quite key to the dash/tcm/ecu talking.

And time is my enemy - truck is a drive away, and weekends are my only time slot, so this will be slow going...

Thx!

 

[Ronmar]

On an A0 chassis and transmission, the engine and transmission don’t need to communicate. the earlier transmissions only really need a throttle position input and they had a standalone TPS sensor to accomplish this. You could probably recreate this configuration and add a standalone TPS sensor to monitor pedal movement…

as I recall reading your situation elsewhere, i did not get a clear sense as to what transmission you had In the truck and what controller you had for it. If it is an older/original transmission in the truck, you will of course need a controller compatible with that trans, but the truck should already be wired for that.

it would then become a matter of providing the appropriate wiring to manipulate and monitor the C7 engine, and of course the throttle by wire pedal assembly To control it…

 

[GeneralDisorder]

Can kind of - I know there's a method to the schematics - have to lookup a quick tutorial. More interested in any lines that had to be added/customized (as you referred to in the other thread). The J1939 is terminated properly, but have to check the j1587, as seems quite key to the dash/tcm/ecu talking.

And time is my enemy - truck is a drive away, and weekends are my only time slot, so this will be slow going...

Thx!

It looked like in your pictures they already swapped in the entire chassis harness including the C7 style PDP, etc....

Making the engine run is easy - the ECM only needs two battery 28v+, and two grounds and a 28v+ ignition switched. 5 pins on the chassis side connector and a way to crank the engine and it will run. You will need the throttle control to actually drive it though.

The biggest issue looked like the trans was the MD3070 and the wiring and WTEC IV are for the 3700SP. They are very similar though so I would *try* to get the WTEC-IV to operate the transmission. It could be that you have to change back to a WTEC-III though.

But yes - as Ronmar suggests - it's a matter of sitting down with the truck and the schematics and finding out what needs to be added, changed, or repaired. This can be a really slow process. I spent about 8 hours last weekend getting a fellow member's truck running after it stalled on the freeway due to an electrical problem. Corrosion in some power/ground circuits to the ECM turned out to be the culprit but in the process of troubleshooting we went down a couple paths after identifying real problems that had to be fixed to rule them out as the cause or to be able to more easily troubleshoot. Burnt out bus resistors, fault codes on other modules, a ground pin pushed out of the chassis ECM connector, corrosion in the CTIS sub harness..... there's rabbit holes that can take days to find the bottom of and that's even with people experienced in the FMTV ecosystem, US Army motorpool experience, etc.