I recently came into possession of a Red Caboose Hi-rail GP9. Beautiful locomotive and Kadee-ready. I'd like to install TMCC but have no clue which setup to use. Has anyone converted one of these? If so, what parts did you use?
Thanks.
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Use the Cruise Commander.
It works much better than a DC Commander would and the slight extra charge will be forgotten when you run the loco.
I'd use the ERR Cruise Commander and the ERR RailSounds Commander with the GP9 sound set.
I think what Matt is getting to, is that the way the motor and gear cassettes are placed in this loco, there's no room left for the ERR board. The original E-unit was custom made by QSI, i think. It sits on top of the motor cradle and runs fore-and-aft nearly the full length of the shell! It's built something like the Atlas SW switcher. If you've ever had one of those on your bench then you know it's a problem child for upgrades like these.
One option would be to put the ERR board in a boxcar or "dummy unit." With appropriate tether(s), it could then be used with any loco. Second option would be to gut your geep and install a Weaver Ultra Line-style single tower chain drive, with underfloor drive shaft. There would be plenty of room for the ERR board in the end opposite the gear tower. Not sure if you're also interested in sound, but there *might* still be room for a small speaker in the cab.
I have a couple of these Red Caboose geeps in 3-rail. I did a Weaver drive conversion on one of them, complete with larger bottom sprocket for a super-slow crawl. If you don't want to be dragging the same boxcar or dummy unit around with you all the time, that's the way I think I would go!
Another benefit of converting... those tall Roco gear cassettes have a tendency to "wheelie" when the loco is pulling a heavy load. Precious "moments!" 
(sorry!) Converting to a Weaver-style drive eliminates this issue. Parts are available, your choice.
Thanks gents. Another thought I just had (that miraculously didn't die from loneliness) is getting hold of a TMCC speeder and relieving it of its electronics. The Geep isn't going to be doing anything strenuous so I'm not really worried about the current draw.
Why not just use the available Mini Commander II, drop me a line and I'll fix you up. That's what is in the speeder, why buy it and kill it?
