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Old 08-23-2013, 08:33 AM
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Yes, your best bet (in my partially uninformed opinion) would be to use a PCM from a 2500 5.7L truck (66RFE trans). At least that way, the trans controls would work correctly. But I'm not sure if the engine controls / emissions are similar enough (between 1500 and 2500) that the engine side of the 2500 PCM would work correctly in a 1500.

Biggest difference is that the 2500 does not have MDS (while the 1500 does). I compared the wiring connector pinouts for the NGC4A PCMs for 2012 MY 5.7L trucks (1500 with 65RFE versus 2500 with 66RFE). All of the connector pinouts are IDENTICAL, except the 2500 has "no connection" at the four (4) circuits that are used for the MDS solenoids in the 1500. Therefore, I suspect (but cannot guarantee!!) that using a 2500 PCM in a 1500 would work fine, except MDS would be disabled.

The MDS solenoids are controlled on the high (supply) side, so having no connection to the solenoid (from the PCM) should simply disable MDS. Normally, this would blow a host of faults (for cylinder deactivation performance, MDS solenoid circuit, etc.) but since you'd be using the 2500 PCM those faults should be deactivated (since the 2500 does not have MDS).

The big issue in my mind is that the VIN in the 2500 PCM will not match the one in your 1500. I don't know how all the module-level security works, but I suspect this could be a problem. Check with a knowledgeable dealer tech and ask them whether you could successfully install a 2500 PCM (new or used) into a 1500 truck.

On the trans hardware end, all the wiring and connections are the same. The 2WD extension IS different (the 2500 uses a larger diameter slip yoke), so you'll have to either swap in the old extension from your 65RFE (which should work) or change the propshaft slip yoke (which may be more of a challenge). The torque converter should actually be identical between a 5.7L 1500 (65RFE) and a 5.7L 2500 (66RFE), so that won't be a problem.

Good luck, and let us know if it all works out!
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