The other day I had an idea to inprove the milage on my 84' F350 crew cab 460 and A/T 2wd. Would it be possible to mount a HD 4 speed transmission reversed behind the stock A/T. This would drive the tail shaft and the driveshaft would hook to end that would normaly hook up to the clutch. By turning it around you could drive it in high, which is 1 to 1, while you are towing. When you are not towing you would run the rear trans in third effectivly changing your final drive ratio to 1 to 2 or higher depending on the gear ratio on the second trans. I'm sure there are a lot of problems with this idea, oiling, gear direction, etc. but problems are were made to be solved. I don't plan on actually doing this but I thought I'd throw it out there and hear what other's say about it.

 

like a gear vendor Over Drive/Under Drive unit?

 

I've actually had that thought too, but the major problem as you mentioned is the direction of rotation, it would be driving on the coast side of the gears, which isn't how they're designed, and may make noise as a result, and may improperly wear the gears as well.Now if you could figure a gear or coupler to mount in front, then it could work.

 

you can find an auxillary trans mission,{yokes front and rear}, and use that. a tranny wont work, unless you can figure out a way to support the front shaft. and like fellro86 said, you would be driving on the coast side of the gears. i have a 1 ton with an older brownlite aux trans behind the 4 speed, it works real well for the design.
also gives you 3 gears in reverse!

i dont think it would be worth the trouble, unless you realy needed an underdrive, and an overdrive real bad. my truck i bought like this and wouldnt change it. only use it once in awhile, but it can be handy.


jim

 

Jimbare
I don't understand, if high gear on the second trans is 1 to 1 (not an overdrive) wouldn't 3rd 2nd and 1st just be progressivly higher overdrives? Please enlighten me, what is a brownlite aux?
Thanks for the input. Steve

 

Final gear, (3rd or 4th, depending on trans) is the 1:1 ratio, the others would be underdrive to it. If you put a higher gear in the axle, this arrangement would work good, as you can double reduce the first tranny's gears. A side shifter would be best, as a shifter setup would be easy.

 

Actually, all the gears would be a severe underdrive as the out put of the first trans would be treated like the flywheel on the second trans and having both in 1:1 would be like having only the original trans in high gear.
You would gain nothing.

The expense and trouble you would have to go through to make the double transmissions work (the second would need to be mounted on and be supported by the rear of the first trans for alignment) would not be worth it at all, not to mention making the drive line too dang long.

However, a gear Vendor O/D or U/D unit would give you 2 rev and in most cases double all but one of the forward gears.

 

I don't disagree, as the GV unit is more effective, and as I said before, the only gain would be if the rear axle were changed to a high axle. Yes, the final ratio still comes to a 1:1, and likely only one gear of the second transmission would be used, as the others would reduce too far, unless you really needed some stump pulling power. Basically, the idea comes from trying to keep it cheap, as unfortunately, I can buy another truck for the price of the GV unit.

 

I still must be missing something! On a normal 4 speed trans ( not an overdrive) installed properly, going from first to 4th does not the engine turn progressivly slower in each gear? For example if the engine turns twice in third gear and the driveshaft turns once, wouldn't turning the driveshaft one time cause the engine to turn twice? Therfore if the trans was turned around and placed behind the 1st trans, with the two driveshaft ends together, every time the 1st trans turned 1 time, the front of the rear trans (now hooked to the driveshaft) would turn twice. As far as length is concerned its a crewcab with the long bed space won't be a problem. Thanks for your input.

 

With the second transmission reversed, yes it would give the effest of an overdrive, but the problem is the noise and reliabilty concerns to that setup. So the next option is turning it around and running it as originally designed, which would then not give the desired effect.