gv's are usually hooked to the back of a transfer case. they are intended to be used at speeds above 45mph. you shouldn't be running above 45mph in 4hi.
<_< Yeah, 55-60 in 4x4 plowing through snow was probably excessive...
How do they work with a manual truck though I though they were just auto trans things that kinda like split the gears? Do I want on of these? Would I then have a 10spd?
The manual kit comes with a switch that mounts on the gearshift, which engages/disengages it.
You can engage it when above ~20MPH if you use the controller(a lot less if you bypass it like I did... not recommended);
2nd over and 3rd over are useful when towing; 4th over is almost exactly 5th, and 5th over is great for highway(1600 RPM @ 60MPH approximately on stock tires).
So you take a 5-speed and make it about an 8 speed.
Unloaded, you just do your normal gears - start in 2nd, go up to 5th, then engage it for double-overdrive.
Loaded, going up a hill, that's when the 2nd over and 3rd over come in real handy.
Remember that the GVOD can be engaged and disengaged while driving, unlike a dedicated "low range" gear transmission. You *do* want to put in the clutch or at least let off on the throttle when engaging/disengaging it, to reduce wear on the conical clutch inside.
I personally love mine(have one on my tan '88), and miss it on my new '93. I'm going to be getting one on there hopefully in a few months when I find the time to fab up a custom adapter(because the GV adapter is expensive).
