The Stovebolt Site Forums The Shop Area General Truck Talk Want A Highway Gear?

I remember dad talking about his young hot rod days. He and his buds would take their Model A's & add a second tranny to the drive train. They'd turn it around backward & weld it to the regular tranny then connect the drive shaft to the "input" shaft of the second tranny. With both in 3rd gear it would be normal gearing. If the second tranny were put onto 2nd gear (assuming a 1.7 to 1 ratio for second gear) the drive shaft would turn 1.7 revolutions instead of 1. Put it in 1st & the ratio would be about too tall for the horsepower of that era. Talk about overdrive.

Thought about doing that myself.

I'm still in the midst of pulling out a Spicer 7041 4 speed auxiliary transmission (2.2 LoLo, 1.2 Lo, 1 direct, .8 OD). Putting it in backwards, I'd still have the 1.2, direct, and .8... but I'd also have a .4!!!!!

Tooooooo much. Besides, figuring a way to do the shift linkage reversal would be a pain. I'm now looking to install it normally and upgrade my 5.13 rear to a 4.10 rear. Nice highway speed at a moderate RPM and an even lower low.

Tiny,

I think I have seen some dope on this idea. I was under the impression that driving any transmission that has helical cut gears in them from the "driven" end would upset any thrust engineering that had been built into that box.

Would the model A tranny from your dad's tale have straight cut gears!

I don't know if my theory has any credence, or was induced by a blow to the head.

Stuart

You could always get a Gear Vendors unit. Keep those low rear gears and still cruise at hwy speed.

Stuart I have no clue as to the gears in a Model A tranny. I'm just repeating what I heard my dad say years ago. I thought it was pretty innovative. You'd have 9 possible forward gears if my thinking is straight. I remember his saying they'd shift both trannys independently with two shift levers.

I think you're right, Stuart. Any thrust washers in the tranny will not have thrust against them, and depending on the design of the gears, I would think that the tooth loading would be wrong.

Model A's had straight cut gears, and I know that the "2 transmission" trick was done. My grandfather's home made tractor had 2 transmissions. That had a flathead Plymouth six and a Model A transmission tied in behind the original Plymouth tranny.

Another idea would be to use the Ranger Overdrive from Advancd Adapters. It mounts in front of the main transmission. It's about $1000 less than the Gear Venders unit.

OK, the gear vendors solution is not an option. I had been in extensive consultation with them ovewr the past 6 months attempting to have a 6 volt unit adapted to my torque tube '45 GMC. They finally gave up on the concept due to the fact that the GM TT's are riveted to the rear end housing. They are very busy and the president did not want to devote any resouces to developing a kit or methodology to the GM TT's. Other makes are still possible, but at this time you can NOT obtain a Gear Vendors unit for a riveted GM torque tube vehicle. Case closed. They need to change their advertising to reflect this as well. The kit, if possible would have cost approx. 4 thousand dollars.
The Ranger is a viable and tme tested alternative. At about 1500 bucks it is a good wat to go. The ranger is about 7" and so the original tranny is pushed back the 7" and the shifter lever needs adjustment. My '45 is pre SM420 so the bell housing would not be compatible with the ranger OD. So unless I find a Truckstell (needle in haystack, I'm SOL as far as OD is concerned. (And no, I will not be removing the torque tube.)

Actually? I was thinking more along the lines of adapting a Borg-Warner R-10 Overdrive unit to the rear of the trans on my '49 big bolt.... I've seen this done to a couple of older motorhomes at a few old car swap-meets..... but untill now? I never looked very close...
The R-10 was used on the Borg-Warner T-85 three speed trans... as used behind the BB Fords (trucks and cars) as well as the Studebaker Hawks and avantii's

Anyone ever look into this mod??

Michael