weird idea
 

I have a 57 F250 that will run a 292 and a rear end with a 4.56:1 ratio. I can only imagine how high the engine must rev to keep up on highway traffic, and what my fuel millage would be. Anyway with such a slow rear end I though of connecting a secound three speed tranny just infront of the rear end. Instead of running it like a normal transmition that slows I would flip it around to speed up the gear ratio.(like a overdrive, but much faster) I know I could not use this in city, but on a strech of pavement why wouldn't it work. I believe I would be able to shift on the fly so with a heavy duty rear end I think it may work. I would like to hear what others think of this idea.

Yup. It is a wierd idea. I like it! If you were a good fabricator, you could make a set of brackets to hold the 2nd trans in place just behind the 1st trans. A pair of yolks would connect them. The hard part would be connecting the (shortened) driveshaft to the rear end. It would need a u-joint on it for sure, maybe a yolk could be welded to the input shaft, it would have to be balanced I think. Depending on your skills this could be the part that shakes the project to pieces...

the only thing there is that by flipping a tranny around, once you got it into first (you would have to shift it backwards!) it would be like having 1.73s!

I had thought of such myself, but one concern was brought up to me... the fact that you would be driving against a side of the gears that was never intended to have full drive force against it, only coast down, so I didn't pursue it from that. If the gears could be rearranged to eliminate that problem, it could work, but most tranny's don't allow for that... The best way would be to swap gears to a real steep highway gear, and have the trans in forward, and have double reduction. Never taken time to try it out though...

he might be right there, run something more like an old 4+4 setup, or grab a gearvendor or similar setup if you got the cash. my dad got a similar one +the truck, but made by us gearand is sandwitched between a transfercase and the diesel 4 speed, not bad for 75 bucks (the 6.9 was gone and the body isn't that pretty)

You DO NOT hook the transmissions up like that, they go rear to the front of another, second one is without a torque converter, I've seen it done either on TV or a magazine years ago. It was 2 older 3 speed automatic transmissions, I wish I could remember how they functioned,

If one had the spare cash then a gear vendors overdrive unit would be the way to go for sure. As they get more popular I was hoping the price would come down, but I think they are still around 3K for a C6 transmission.

ideas
 

Snow, thats not a weird idea at all, I like it ! But some folks would call me weird. Anyway, the fellow who mentioned that fact that you would be using one tranny on the coast face of the gears is correct. Now, if you were using something big asnd sturdy, likea NP435, for the secondary trans, maybe it wouldn't care, I don't honestly know. But there ARE secondaries already made for exactly what you have in mind. You might like to look for a 3 spd 'brownie' , I think they were from spicer IIRC. The 3 speeders had several ratios available, some of them were 2.17/1.00/.75. Memory is fuzzy here, very fuzzy, but what you want DOES exist. How common or easy to find, I don't know. DinosaurFan, @ work on lunch

I remember my dad talking about a brownie that was in a gas powered singleaxle tractor (big truck, not john deere) he said you would have it on the low side out in the field but when you got onto the road it would force the auto tranny to go through the gears again.

same theory at least, but you have a manual, correct?