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Old 12-01-2019, 12:46 PM   #1
jw hash
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Default F150 overdrive

I`m putting together my 68B Cabriolet and I`m going with the F150 set up with overdrive, it is my understanding that there is different overdrive gear ratio`s what one work the best for a pretty much stock Model A. Thanks John
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Old 12-01-2019, 01:49 PM   #2
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Default Re: F150 overdrive

I have the setup from the early '90's by Dave Delmue in Cal. Not sure what the ratios are but an RTS T170FT (which I think Dave uses) tranny is set up for D18 or D20 alum cases. Ratios are 1st 3.25 to1, 2nd 1.92 to 1 3rd 1.0 to1, 4th OD .78 to 1. (approx 27% OD)
My 1st and 2nd gears appear close to stock A box ratios with 3.78 rear end, heavier tn sedan.
See if you can find the Vince Falter Ford Garage website for some explanations and the Tremec T170 RTs tranny. He has great charts with Id numbers and OD options..

Last edited by duke36; 12-01-2019 at 01:59 PM.
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Old 12-01-2019, 02:42 PM   #3
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Default Re: F150 overdrive

There are 3 OD ratios available on the RTS transmission. 27.6%, 37.9% and 41.1%.
With a stock engine a 3.78 rear end ratio and a 27.6% works very well. The 68B is fairly light so you might be OK with a 37.9% particularly if you have no high hills to climb.

We have a'31 Slant with a 37.9% and 3.78. It has a touring engine and it works well.
We also have a '30 TS with a 27.6% and 4:11 with a touring engine. It also woks well.
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Old 12-01-2019, 03:45 PM   #4
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Default Re: F150 overdrive

I have the 41.1% in my speedster which has a lighter body and improved motor and it pulls that ratio effortlessly. However, I was told that the 41.1% was ideal for V8s and the 37.9% for Model As, but as previously noted, I suspect it has a lot to do with the weight of your car and a Fordor with standard motor would probably be best with a 27.6%. The numbers cast on the side of the box are the code to which ratio the box has, but it is some years since I located the data on the codes.
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Old 12-01-2019, 04:56 PM   #5
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Default Re: F150 overdrive

Quote:
Originally Posted by duke36 View Post
See if you can find the Vince Falter Ford Garage website for some explanations and the Tremec T170 RTs tranny. He has great charts with Id numbers and OD options..
Big fan of Vince's Ford Garage. He has a ton of info. http://www.fordgarage.com/pages/TremecT170FT.htm
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Old 12-01-2019, 06:34 PM   #6
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Default Re: F150 overdrive

I wish that there was still parts support for these units. The best parts sources are the guys that do the conversion packages.

The Type B gears have the least amount of drop in the gear change so they pull well and are like a close ratio set. The type C has a bit more drop then the B set. As was mentioned the type D gear set has a pretty steep drop in rpm so the motor would have to be able to pull that. The codes are on the trans tag for ID but the conversion guys will set you up with what ever you want.
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Old 12-10-2019, 05:56 PM   #7
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Default Re: F150 overdrive

I want to do the same conversion but am not finding any local machine shop capable of cutting, turning and resplining the trans shaft. Does anyone have a source for this that I can sent it to?
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Old 12-11-2019, 03:33 PM   #8
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Default Re: F150 overdrive

Quote:
Originally Posted by T&A Flathead View Post
I want to do the same conversion but am not finding any local machine shop capable of cutting, turning and resplining the trans shaft. Does anyone have a source for this that I can sent it to?
I had mine done at a small shop locally. But... When I was looking for someone to re-spline mine, I found this thread. I called Tim and he said he has a shop near him that still does it.

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Originally Posted by MurphyJ View Post
Another source for a Ford F-150 OD transmission is Sheridan's Repair in Nunica, Michigan. Call Tim Sheridan at 616-836-6477.
https://www.fordbarn.com/forum/showt...?t=5594&page=4
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Old 12-11-2019, 03:58 PM   #9
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Default Re: F150 overdrive

I may be wrong BUT isn't there someone who adverizes in the the Restorer who makes a "slip on" piece to the mainshaft to fit the pilot bearing and give the correct length??
Paul in CT
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