I've got an 89 GMC 1500 4wd Suburban. It's throwing a code 24. I've managed to find out a few things, but the haynes manual is remarkably silent on the subject.

1: speedo works, so that's not the problem.

2: There's apparently (I'm sort of running on assumptions here) 2 possible parts broken, a piece behind the speedo (?) or a VSS at the tranny or transfer case. When I ran the loaner OBDI interface at autozone, it said that the VSS was showing a short.

Since I don't want to just throw parts at the problem without knowing which parts (or wires) could be the issue, does anyone have a stepwise troubleshooting list for this problem? Preferably with a photo or diagram of where the VSS actually is?