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16197427 PCM, 4L60E. How does the 4wd low input wiring work on the F8 pin for the PCM? Do you just have that wire grounded when in 4wd low? Supply power to it and remove it when in 4wd low? This is the last thing I need to figure out for the 16197427 PCM swap...
http://www.gearhead-efi.com/Fuel-Inj...3&d=1331491876
As far as I know the 4wd LOW input was only used on the 4L80e trucks because they use an input shaft speed sensor. Without the input it would cause gear ratio errors.
The 4L80e's used a three wire T-case switch while the 4L60e's used a two wire switch.
4l80e's have an input and output speed sensor on the unit itself so it wouldn't really need to filter 4wd low input for shifting....
The 4WD 4L80e uses the output shaft sensor in the T-case. So they need the 4wd low input to ignore the gear ratio difference created by gear reduction. The 4L60e doesnt.
You're saying this but I am experiencing otherwise, hence why I need to figure this out. Why else would the $0D bins have the option to filter 4wd low input if it didn't matter with the 4l60e? Why would there be a low range ratio option in the $0D if it didn't need it for the 4l60e? All I need to know is how the circuit works and I cannot find any proper wiring diagrams anywhere... I'm just going to try using my voltage ohm meter and test different theories I have with a low amp inline fuse and see if I cannot figure something out and put it here for anyone in the future.Quote:
Originally Posted by brian617
Should be switched ground input.
What are you trying to accomplish with the input signal?
You'll have to buy a three wire T-case switch for an 4L80e equipped truck and add the extra wiring to the harness.
Try looking for a k2500 wiring diagram, maybe in the $0E info on this site.Quote:
Originally Posted by c5wagner
93+ 4l60e 4x4 uses only the speed sensor in the transfer case output. For 4 low the switch on the transfer case provides a ground input to the PCM pin to adjust the shift speeds. Not all transfer cases have the correct internal rail to work with the 3 pin switch. Only the 93+ np241 has the correct shaft to my knowledge.
As to the 4l80e, there is some confusion here for 4x4's. 91-93 4x4 4l80e's had both an input and output speed sensor in the trans, and a speed sensor in the transfer case. Both input and output speed sensors run directly to the PCM for them, so they require no 4x4 low input. In a 94+ 4x4 4l80e the output speed sensor in the trans was omitted, and the 4 low input switch was hooked to the PCM to tell it when to correct the speed sensor reading.
In my old 94, the 4WD low input changed the shift tables, because IIRC 93-94 shifted by MPH and not RPM. Mine was actually incorrectly plugged into the EGR wiring when I bought the truck and it was all screwy. It would be fine cold and then think 4lo was engaged when the EGR warmed up to active and would shift to OD by 12mph. That took me a little while to figure out...haha
I don't have a chevy transfer case so the switch wouldn't have mattered as I have a jeep np231 with a JB conversions GM vss SYE. I did wire a plunger switch that the transfer case shifter activates in 4wd low that grounds pin F8 in 4wd low only. Everything seems to be working flawlessly now.