Ford AA truck underdrive used as an overdrive

[Studebeggar]

Model AA trucks had an underdrive unit to lower the gear ratio,has anyone tried to turn one of these around to use as an overdrive ??? someone said they were noisy and/or not the correct ratio, I want to install a overdrive in a pre 1930's car.. Spencer, desert country calif.

[critterpainter]

I've had people tell me "allya gotta do is turn it around" But when I asked for more info all I ever heard is "a friend of a friend of a friend may have done it"<BR> does the car you wish to put OD into have a closed or open driveshaft? And the Big question....does the engine have the power to pull the taller gear??? (Hint a Model A ford cannot easily handle a OD without increased compression...been there--done that)<BR> My favorite "modern" od unit is the one used in the 70's though early 90's Volvo,<BR> Although I have not used one myself, I have seen some very neat installations.<BR> Bill

[ply33]

<a href="http://www.skinnedknuckles.com/"><span style="font-style: italic">Skinned Knuckles</span></a> had an article on the "Effects of Rear Axle Ratio on Antique Car Performance" in its September 2000 issue.<P>As it turns out, changing to a "taller" final ratio may not help you on top speed or increased cruising speed. Basically the same thing that Critterpainter just told you. On the other hand, for some cars it will help. You can either try it and see, or do a lot of engineering analysis first and see if you should just save your money.

[Mark Huston]

I have used the Volvo OD in an antique car. A friend of mine here in Northern California is a machinest and he set up the conversion for me. I had a 1928 Studebaker President with a 4.3 rear end. The car was about a 50-55 mph car with the stright 8 engine and that low rear end. With the mid 70's Volvo 4 speed OD I had a car that cruised all day at 60-65 with no sweat, had it up to 75 one time for couple hours crossing the Salt Flats of UT. With the Volvo transmission in overdrive my ratio worked out to 3.4. There was a lot of machining that had to be done, new drive shaft made, etc. The only problem that I never worked out was the parking brake. The parking braked worked off the back of the old transmission. Could not do that with the Volvo OD unit. My friend has put these Volvo unites in several cars including other Studebakers, a 1933 Marmon and a few others. It is a good unit. I made one trip with the Volvo OD in my President where I drove for 2 weeks, 3,000 miles through 5 states. Over many mountains and when I needed extra pulling power I either down shifted or kicked it out of overdrive. When I was off the grade kicked it back into overdrive. Worked perfect. If you got a engine with the right horsepower, the time and money to make it work, it is a good way to go. The only draw back is you can forget about ever showing your car again, unless you want to be in the modified/hot rod class, and it might effect the value of your car on resale down the road.<BR>

[Guest]

They work very well in pre 1916 auto's in the 25 HP range. A fellow in Conn. has a 1912 Overland Moder 59 Roadster and has been running one for 30 some years and he just loves it. It is a closed drive shaft type.

[ronbarn]

Pre16, Can you give us more details on the Overland OD - type and make? How it was installed on the closed drive shaft? etc.

[Guest]

Model AA Ford underdrive reverced. modify the input and out to match with overland inclosed driveshaft . The drive shaft was shorten and AA ujoints and flanges were used. he made a lever looking like the gearshift and mounted it to existing quadrant.reduces eng RPM by about 440 revs, which is really nice an a 25 HP auto. He is in southern conn. Doesnt hear well but I could give tele # if you wish.<BR>Just cant waite to get back to yellow swamp, next month. lburt@maine.rr.com check my ebay spot Pre16 under sell

[Studebeggar]

Thanks everyone...Critterpainter,Ply33 ,Mark and pre16..Mark I'am also in the ASC and saw you in Sutherlin a few years back..Yes Pre16 I see you a lot on Ebay ..I have a Model AA under-drive but the ratio seemed high.. but it was easy to shift gears ....I was planning to put an overdrive in a 1924 Studebaker Special six tourer.. Spencer Carl , Bishop ,ca.