NP241C in a 85 Squarebody

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usar17

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Ok so i figured this forum would be better then the 80s Truck forums because it has to deal with the wiring of 90s trucks more so. Situation: I have an 1985 that im rebuilding. 350 TBI Engine, 4L60e Transmission and all wiring are from a 1994 K1500. The NP241C transfer case is from a 1990-91 Suburban (passenger drop).

Now i know the newer 241Cs had a 3 wire indicator switch by the shifter. For reasons of TCCM, indicator lights, and front Diff lockup. My 241 is 2 wire indicator, my 94 wiring is for 3. Now it seems the wiring only goes to front diff and the ABS system. I dont need the front diff wiring or the ABS crap. Do i need to worry about anything with the indicator for the PCM or can i just have the switch turn on the 4WD light on my dash? I dont think there is a TCCM, not sure what year they brought that in. The t-case is manually shifted. Thanks
 

TylerZ281500

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with manual shift its mostly mechanical, very little is pcm controlled if you dont need the front diff, only thing pcm runs off of back there is vss i beleieve and if i remeember thats not even the same part of that harness.
 

usar17

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PCM gets its vss from the same harness as the transmission. The wiring I pulled from the 94 seemed to just go from the indicator to the floor indicator lights and to the abs system and the front differential. I wasn't sure if the pcm or anything needed to know about being in 4wd hi or low
 

usar17

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Well....i hooked everything up. But my pcm is getting a "4WD Low: ON" signal somehow. Any clue from where? Which pinout in the plugs would do this. Id assume it not being hooked up would have prevented this but maybe it needs ground or something to know its NOT in 4wd low.

-Shawn
1985 Chevy k10 w/ 92 TBI, 94 4l60e, 91 NP208
 

usar17

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You must be registered for see images attach
Found the issue thanks to google. For anyone using a 1994/95 system with manual T-Case shifting: the 3 wire connector that goes into the T-Case is 12v! It controls BOTH the front axle actuator AND in LOW signals the PCM to stay in 1st gear. See attached image. This is good to know for anyone mixing wiring harness or PCMs.

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