I have a '54 Tudor Sedan "P Code" car with 256 Y Block engine. It had a standard 3 speed transmission which I am replacing with a 3 speed overdrive. The car has 3.90 gears in the rear axle now but I have the 4.10 "pumpkin" which was in the car from which I pulled the O.D. transmission. In my experience, Ford usually fitted the O.D. cars with the 4.10 gears. What are the advantages or disadvantages of leaving the 3.90's in the car after the switch to O.D. vs. replacing the "pumpkin" with the 4.10's? Thanks, Alan S. Freeman

I'd just drive the car. I've had 4.56, 4.11, 3.7, and 3.33 in my birds. Different 3 sp o/d, 4 sp w/od, and T-5. Little lighter, and all 312's or more. The main thing is the car, given displacement, cam, weight, typical roads, is fun. If it feels sluggish, and the motor's tuned, change the gears. With a couple switches, the o/d can be engaged or disengaged at lower speeds, dropped out without the WOT sw, and sometimes 2nd over was a good gear on the back roads.



But back in the day, the 4.56 or so, out of the 6 cyl o/d wagon, with the t-85 o/d sure beat a lot of vette's on the street.

miker
55 bird, 32 cabrio F code
Kent, WA
Tucson, AZ

Hi Alan,



The ’54 Ford is a fairly light car… just over 3,000 lbs., as I recall. Thinking of the horsepower and torque of the original standard equipment 239 engine or even the 256 that came in yours and was standard in the Mercs, Ford needed to use the 3.90 or 4.10 gears to make the car 'driver and street/highway performance friendly'.



As miker says, considering:

-    engine displacement (you said you’ve got the 256 displacement)

-   camshaft (assumed to be basically original in terms of not having long duration, high lift, or excess overlap)

-   1.43:1 rockerarms

-   compression ratio (7.5:1 with the 256 engine; 7.2:1 with the 239)…

the engine was tailored for stop-and-go, low speed city and elevated speed highway driving. Remember, in 1954, the highways of the day were significantly different than our interstate and intrastate roads today. 70 mph seemed faster then than it seems to us today because of our improved roads.



In its day, in good tune, the new ’54 o.h.v. engine was considered to have improved throttle response and power. Because of the improved suspension, the ’54 car significantly outperformed the ’53 Ford with flathead engine that it replaced.



Ford had reason to change the rear end ratio with the overdrive option. The overdrive reduced engine r.pm. by something like 28% (I’m rusty on this) in 3rd gear. They went to the 4.10 when the overdrive was installed to obtain a final drive ratio that would work with the engine horsepower and torque curve to provide acceptable quality of acceleration and pulling capability (inclines/ hills) as the straight three speed transmission equipped vehicle would have at the same intended operating speed.



The original 3 speed and 3 speed overdrive transmissions were light duty units. IF you do run in 2nd gear overdrive, I would recommend not driving ‘hard’ with it. The R-10 overdrive unit with three planetary gears (not four like the R-11 units) will NOT hold-up to hard acceleration, it’s really not designed for it.



Changing gears in the original ’54 readend assembly, is not easily accomplished. Certainly, it can be done. Like miker, I’d recommend leaving the rear gears alone, at least initially. I think you’ll find the ride 'driver friendly'. If you do feel it’s ‘doggy’, then go through the effort of changing the rear gears.



My first car, when purchased, was a drivetrain-less ’54 Ford business coupe. I initially made it road-able by installing an o.e.m. ’54 239 engine and 3 speed overdrive transmission. Because the engine and trans. were a ‘transplant’, I had the 3.90 rear end gears that the original 239 three speed trans came with from the factory. The set-up was quite okay. I did install a ’54 Merc single quad intake and teapot carb. and ’55 dual exhaust manifolds to make it ‘funner’.



Hope this helps a bit...



Regards,




NoShortcuts
a.k.a. Charlie Brown
near Syracuse, New York

Gear selection just depends on how you drive.  If you do a lot of highway driving then the 3.90 gears would be my choice.  My ’55 Customline with 272 now has the 3.56 rear gears with the 30% T85 overdrive and is right at home at highway speeds.  It originally had 3.89 rear gears with the overdrive.  With the 3.56:1 gearing, the car is quite comfortable running at 70-75 mph.

Lorena, Texas (South of Waco)

Thanks everyone. I will leave the 3.90 gears in the car to see how it performs. I would prefer that the car cruise nicely at freeway speeds even if the car is a little slower off the line. Alan

My 58 has the 3.89 gears, 3 speed od. Stock 292, headers, holley 600. Very drivable combination, gets about 16 mpg on the highway. I was thinking about dropping down to a 3.70 to lower the rpm on the highway. I'd try it and see if it works with the smaller engine.





thanks, Mark