OVERDRIVE?how bout a 3 speed O.D.

[CHEVIBUBBA]

a friend & i were talking & i had a flash;
install a 3 speed manual backwards behind your tranny of choice.
i don't know the ratios of the 3 speed but it may handle the torque.
anyone here a guru on 3 speed manuals?
can you turn this tranny backwards reliably?
just a thought but if possible,using first gear in the manual & 3rd in a th350 would be a MEGA O.D.!
any thoughts?

[SB_in_SC]

With a O/A torch, a welder, and some imagination, ANYTHING's possible! Let us know how it turns out. You might start a revolution.

[Palf70Step]

you could install an aftermarket OD unit which would give you three more gears, and probably be cheaper and easier in the long run.

[cdowns]

helical gears are designed to spin in one direction for proper operation

[1969 GMC]

there have been a few guys over on Pirate 4x4 that installed a NP203's range box backwards in front of a NP205, which gives a 50% OD when engaged. it can be done!

[CHEVIBUBBA]

Originally Posted by cdowns

helical gears are designed to spin in one direction for proper operation

thats what i was afraid of.
i'm not giving up though.

[Bowtie67]

years ago we took an old Model T and put a 6cyl, truck 4sp & a later diff with duel wheel axle in it to use for pulling cars and such out of the woods, the 6 was totally stock and really had no power and the gears were a little too tall for towing anything so we added another 4sp behind our current 4sp to get double low gears, this thing if you could get traction could pull dozers. although we had 16forward gears and 2 reverse gears when you put it in 4 & 4 you are still at 1 to 1 ratio from the engine, 500rpms on the input shaft from one trans in 4th gear still turned the output shaft of that trans 500rpms.

This past weekend I finally saw the last episode of Copperhead where tracy was actually driving the truck and had an elctronic OD unit hooked up to the turbo400 trans, this was cool because you could turn it on anytime in any gear. the only better solution to this is an actual later model 5sp, the 700R4 in my truck when it goes into 4 also locks up the TQ converter and is a big jump from 3rd gear. the only thing I dont know much about is the later truck 5speeds and how much thrashing they can take, if it is a moderate or even performance engine and your not banging gears this would be an excellant option. IMO

[CHEVIBUBBA]

thanks for the story.thats kinda how the idea started.
the friend was talkin about stakin 3 speeds.i told him it would still be 1:1 out.
but backwards it would be od in 1 & 2.
i have a 4l60 in my truck w/a vigilante 3500 rpm stal lockup converter.
having it lockup only in 4th was not gonna work so i rigged it to lock in 2-4.
much better economy.
the 5 & future 6 speed auto's are interesting but, wouldn't it be cool to have a .5 or .6 od?
especially if it only cost $150-$250 when the time to rebuild comes?
the development cost may be high but, once done, everyone with a chevy drivetrain can have great od w/o $2k-$6k conversion bills.
which is the main drawback to the gear venders & late models imo.