upgrade to '7427 from '7060 - ready to pull the trigger

[Daveo91]

I've redone my Excel for the '7060 to '7427 conversion. I added a sheet that starts with pin A1 from the '7060 with description, wire color and mapped pin on the 7427. Should be easier to use during the actual re-pinning procedure as @1Project2Many recommends.

The questions I still have regarding this conversion have been consolidated down to those associated with the 4wd speed sensor differences between the '91-'93 7060 and the '94-'95 '7427.

7060 has five pins associated with speed sensors: B5 and B6 from rear (output) trans sensor, B9 and B10 from front (input) trans sensor, and B11 from DRAC which comes from sensor on output of T-case.

7427 also has five pins for speed sensors, but some differences: F2 and F3 from input trans sensor (map to 7060 B9 and B10), F8 is a 4-low signal from the t-case lever (grounds when in 4-low), F12 is trans output speed that comes from DRAC, and F13 is called vehicle speed signal but also appears to come from DRAC.

- Trans input speed sensor connections are easy. Direct match between old and new PCM. Wire colors are even the same.
- 4-low signal at F8 is also easy. To figure out at least. I have to add a switch at the T-case lever that will ground that signal when lever is moved to 4-low. I have a plan that I think will work.
- It's the connections at F12 and F13 where I get fuzzy. At F12 I currently have it mapped to 7060 B11, but I'm not sure that's correct? I did it that way since they are both brown wires that come from C13 terminal on the DRAC.
- My main question though is F13. on 7427 this is a dark blue wire that also comes from the DRAC (Pin C11), but on the 7060, there's only one wire that comes from DRAC. I could map 7060 B5 (trans output) here, but not sure?

Why does the 7427 need two signals from the DRAC? In reading, it seems like one is 40 pulses per rev, the other is 2000 pulses per mile? Can I get both signals from my '91 DRAC? Or do I even need the second signal? (I did go to pick-n-pull and bought DRAC from a 1/2 ton '94 4x4 Burb. But then I'd have to reprogram that to get my speedo correct?)

One more question: does anyone know where the DRAC is on a '91 squarebody suburban? I'm not seeing it mounted by the PCM and I recently had the gauge cluster out for something else and I don't remember seeing it in there, but I wasn't looking for it. Maybe behind the radio?