Hi-Lo with internal gears - the dream AA accessory

[M2M]

pg35 Hi-Lo Transmissions.pdf

[M2M]

Could you fit this to an A? Or is it strictly for AA? Hi-Lo tranny sold well on the TT but it was made as a rear mounted unit not front.

[updraught]

You could fit it to a car ... but then the rear wheels would be about three feet behind the back of the car.

[M2M]

Originally Posted by updraught

You could fit it to a car ... but then the rear wheels would be about three feet behind the back of the car.

Well no; you could shorten the driveshaft or lengthen the chassis. Don't people cut the driveshaft to fit an o/d on an A?

[Joe K]

Sort of a difficult alternative for the Ruxtell Model AA Overdrive.

I had an AA I was fitting a Ruxtell to. It is possible as it replaces the "Dual High" of the AA truck in the 28-29 model years without change, or the "intermediate shaft" of the 30-31 AA with Borg Warner rear with various "adaptations" which are covered in the "Green Book."

Funny the ad doesn't mention intermediate/dual high design (which was mis-named as it was a "dual low.") Instead "lengthening" the frame with sister plates?

Unlike the Ruxtell, I don't imagine a lot of these were sold.

Joe K

[Neil Wilson]

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Originally Posted by M2M

Attachment 408335

FYI - The link shows the transmission installed in an A chassis with a frame extension (see wheel style). However, the text indicates it is for an AA.


The only Twin High - Hi-Lo transmission I have seen was fit to an AA worm drive shortened torque tube. So, not frame extension needed.

[Joe K]

Neil, it looks to be a pretty well thought out setup. Unlike the Ruxtell which requires trimming of the AA truck cross-member to fit.

As to Model A, I have often thought a "dual high" of AA fame could be "adapted" to Model A overdrive use by "reversing it" and putting it in backwards. No doubt this will require a change to the torque-tube/driveline and change to the dual high as well.

Dual Highs can still be found for $75 though. One can do a lot of re-engineering at such a low starting price.

Joe K

[M2M]

Originally Posted by Joe K

Neil, it looks to be a pretty well thought out setup. Unlike the Ruxtell which requires trimming of the AA truck cross-member to fit.

As to Model A, I have often thought a "dual high" of AA fame could be "adapted" to Model A overdrive use by "reversing it" and putting it in backwards. No doubt this will require a change to the torque-tube/driveline and change to the dual high as well.

Dual Highs can still be found for $75 though. One can do a lot of re-engineering at such a low starting price.

Joe K

What is the gearing of the "dual high"? Could you perhaps use it as an underdrive on an A with has hi-speed gearing of 3.27?

[Joe K]

The Ford Dual-High (two pedals on the floor and fitted after a three speed Model A Transmission) was reported in the period literature as a "30 Percent Increase in torque" or conversely a 30 percent decrease in speed. Unlike the Ruckstell, which had overdrive AND underdrive, the Ford Dual High was underdrive only (two speeds) depending on which of the two pedals you pressed.

I could see using a Dual High ahead of a 3.27 rear. It would give you a gear stagger which would more closely approximate a four speed - and you could "mix it up" in your shifting/timing just for the additional challenge.

More on someone over at Jalopy Journal (Hamb) who looks to retrofit a Dual High to a later Ford 1 ton truck. https://www.jalopyjournal.com/forum/...nto-38.862467/

That "Dual-High" is actually an underdrive to 'gear-down' for more power(roughly 30% drop as opposed to your expected 30% raise) in those under poweres/overloaded commercial vehicles from the 'day'

Joe K

[M2M]

"Reduces speed by 32%, gives 47% more pulling power"

Why the difference between the two numbers?

[Joe K]

Jim Schild's "AA Truck Supplement to the Restorer's Model A Shop Manual" phrases it this way (apparently a reprint of period literature):

" Dual Transmission - Constant mesh planetary type. Gives 68 percent as much speed and 147 percent as much pulling power as standard truck."

These numbers are more consistent as the ratio of speed 68/100 is the inverse of torque/power/pull 147/100.

If one reduces the 100 speed by 32 percent, one has remaining 68 percent.

So your cited ratio is consistent with published data.

Just not said consistently.

Joe K

[M2M]

Originally Posted by Joe K

Jim Schild's "AA Truck Supplement to the Restorer's Model A Shop Manual" phrases it this way (apparently a reprint of period literature):

These numbers are more consistent as the ratio of speed 68/100 is the inverse of torque/power/pull 147/100.

If one reduces the 100 speed by 32 percent, one has remaining 68 percent.

So your cited ratio is consistent with published data.

Just not said consistently.

Joe K

Okay, thanks; makes sense now.

Maybe a dual-high gives us a poor-boy's Mitchell option for an A? For example, you run a 3.27 rear then add 5.50x19 bias ply tyres which brings you to around 3.08. Hit the 32% dual-high underdrive to give you around 4.08 in top gear.

I don't know though how viable it would be to fit an AA Ford dual-high to an A. If it could be installed reasonably easily and not cause any problems it could be an option.

[Railcarmover]

Okay,lets review...puff,puff,PASS..you've got to pass that joint,you just don't keep on hitting it,you get all kinds of crazy ideas,its why they call it dope..

[M2M]

Originally Posted by Railcarmover

Okay,lets review...puff,puff,PASS..you've got to pass that joint,you just don't keep on hitting it,you get all kinds of crazy ideas,its why they call it dope..

Dude...people are fitting o/drives from Volvo, Jap cars, modern cars, you name it...so why is fitting an underdrive from an AA (same make and era to an A) more crazy than all that? Or more crazy than The Jetsons Model A engine pic on your profile? You cannot have it both ways.

[Railcarmover]

Well,its clear you don't have a grasp on modifications for speed..so hey,knock yourself out. Me? I'm gonna rock double the power of a stock car,with the B cam along with the other improvements my 'Jetsons' power band is about 2800 rpm max torque rise,in front of a 26% mitchell I can go from five to fifty miles and hour with one synchronized shift if I split 2nd gear.Or run it in high range all the time..

Gearing cant create power no matter how twisted up you get..underdrive,high rear end big tires what ever you still have about 38 horsepower max rise @ 2200 to play with..basically a 'Flintstone'

[M2M]

Originally Posted by Railcarmover

Well,its clear you don't have a grasp on modifications for speed..so hey,knock yourself out. Me? I'm gonna rock double the power of a stock car,with the B cam along with the other improvements my 'Jetsons' power band is about 2800 rpm max torque rise,in front of a 26% mitchell I can go from five to fifty miles and hour with one synchronized shift if I split 2nd gear.Or run it in high range all the time..

Gearing cant create power no matter how twisted up you get..underdrive,high rear end big tires what ever you still have about 38 horsepower max rise @ 2200 to play with..basically a 'Flintstone'

Nice rant. I didn't think the Jetsons comment would cut so deep; I must have hit a raw nerve. Serves you right for that bizarre, out of nowhere comment about weed. Above, I never suggested anything is a good or bad idea, or for anyone to do anything; and who said I know or care about speed...this is a forum about Model As...people brain storm, debate things, joke around and BS a little...that's what people do on forums. If you think a dual-high is a bad idea on an A why not explain why you think that rather than be an a-hole?

IF it fits; a dual-high on a A is absolutely an option (as someone else also commented above)...is it a good option compared to other options? I never said it was. You should learn to read and think a little. You wrote "Well,its clear you don't have a grasp on modifications for speed"...why do you assume what I was discussing had anything to do about speed. Don't assume other people share your worldview of the Model A hobby. My interest is not speed, it's about being able to drive at 50-55mph without the engine screaming.

You wrote "Gearing cant create power". Apart from being wrong, it's bizarre that you would say that being you're using a Mitchell. Get a grip on yourself.

[Joe K]

I think anyone mechanically minded knows what they're getting into when they fit an overdrive into a (essentially) low powered car. However it may be done - and there is more than one way.

Maybe we can focus on those alternatives rather than create invective? We are a technical board.

Joe K

[Railcarmover]

Originally Posted by M2M

Nice rant. I didn't think the Jetsons comment would cut so deep; I must have hit a raw nerve. Serves you right for that bizarre, out of nowhere comment about weed. Above, I never suggested anything is a good or bad idea, or for anyone to do anything; and who said I know or care about speed...this is a forum about Model As...people brain storm, debate things, joke around and BS a little...that's what people do on forums. If you think a dual-high is a bad idea on an A why not explain why you think that rather than be an a-hole?

IF it fits; a dual-high on a A is absolutely an option (as someone else also commented above)...is it a good option compared to other options? I never said it was. You should learn to read and think a little. You wrote "Well,its clear you don't have a grasp on modifications for speed"...why do you assume what I was discussing had anything to do about speed. Don't assume other people share your worldview of the Model A hobby. My interest is not speed, it's about being able to drive at 50-55mph without the engine screaming.

You wrote "Gearing cant create power". Apart from being wrong, it's bizarre that you would say that being you're using a Mitchell. Get a grip on yourself.

I guess you decide what is a joke,or BS..thanks for clearing that up. Gearing allows you to utilize power is an manner that better suits the task,but it doesn't create the power to perform the task.

Since you introduced bizarre,allow me to respond,don't you think its a bit bizarre to effect a gear reduction only to turn back and increase it? why not utilize a gear increase and be done?with overdrive and direct you don't have to change the rear ratio and tire size along with machining and installing the dual high....oopps did I just say 'high'..

[Chris Haynes]

Didn't the folks at Mitchell solve this overdrive issue a couple of decades ago?

[M2M]

Originally Posted by Chris Haynes

Didn't the folks at Mitchell solve this overdrive issue a couple of decades ago?

You're right, they did; that's not in question. This thread is/was about accessory underdrive trannys for AAs which then drifted into a "what if..." about fitting an AA underdrive into an A with high gearing. No one has tried to force anyone to think or do anything.