Aren't you going to use a TBI drac? Speedo gets 4k (right??). PCM gets 2k to F13 and 4k to F12 (tranny speed). I honestly have no idea why GM felt they needed to feed the tranny code a 4k signal, unless maybe the tranny code was developed on a TPI car PCM that was always 4k..
With F12 vs F13, I hacked a patch to use F13/2k input for ALL speed related stuff because F12 is needed for MAF input ($0d_maf), and it's silly to be switching pins to change between MAF and s/d chips. dimented told me this was a bad idea (on TGO) because tranny code "needed more precision" than 2k, but I disregarded his advice because he runs manual tranny's =).
The alternate solution for changing between MAF+s/d is to use the 8625 PCM, which supports alternate TIS/TOS inputs on F2-F5 (flag in bin, but wiring this way is PITA).
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