Did you read all the previous messages GSHOOLEY? Go back and do so, you'll find that there was some good info posted (mostly by me, but not all). Not trying to bust your chops, meant above in a friendly manner!
Because of the possibility of blowing out the planetray gears, seal issues, and reverse problem (can't backup if in OD), I wouldn't use one. Instead, I'd get a beefy old three speed tranny and mount THAT behind the transmission. Remove first and reverse gears from the trans so there is only 2nd and 3rd. You'll need to cut the input shaft of the tranny down and make a slip coupling between the output of the original trans and the cut down input of the second trans. In 3rd (direct drive) everything is as normal. When in 2nd, you have a lower range.
So how does this replace an OD? Change the rear axle to a high gear. Instead of running a 3.73 or 4.11 gear, run a 2.50-3.08. You may need to put the second trans in 2nd gear to take off, then shift to third for driving. For short trips just leave in third. Shifting the second trans is easy -- either use a solenoid and electric switch, or use a heavy duty choke cable. Pull for one gear, push for the other. Just don't shift whith your foot on the gas, vehicle should be "coasting" with no "bind" on the trans at all -- accelerating or braking. Would be a great for a street/strip car! For a 4x4, leave first and reverse. Both trannys in reverse would make an ultra low granny gear!
Shifting gets complicated if both shift levers are used though. You want to remove first and reverse to prevent accidentally slipping into those gears for one thing, to reduce drag inside the trans for another. Leaving in first/reverse could get you in trouble, and you'd have to mess with two cables (one in neutral, the other in gear) or figure something more complicated out.
Last edited by farna; 12-20-2005 at 12:34 PM.