Topic: 1946 Rear Ratio


Steves46    -- 09-18-2011 @ 7:58 AM
  I read somewhere that the rear ratios for the 46 cars was 3:54; and then was switched back to 3:78 in 47 & 48. Is that true? I tried locating the stamp on the bottom of my differential but have been unsuccessful trying to locate it.


supereal    -- 09-18-2011 @ 11:34 AM
  If there is a ratio stamp, you will find it on the "web" of the banjo on the bottom side. It will be expressed by a series of numbers. For instance 3-78 will be stamped as "349". 3-54 will read "3911". We use a ScotchBrite pad and a bit of solvent, such as "Super Clean" to help locate the numbers. Not all rear ends were stamped, and it isn't unusual to find that the gears were changed over the years, but the stamped numbers were not. I've seen a few 3-54s in '46, but mostly they are 3-78s. The 46 cars were often non "standard" as the race was on to make them immediately after the war. If you don't have the Club's fine 41-48 book, be sure to obtain a copy. It will tell you more than you probably want to know about the cars of those years. It is a gem!


ford38v8    -- 09-18-2011 @ 11:52 AM
  Steve, ratios were not assigned by year, but by engine, weight of the car, expected terrain where the car was sold, and by the driving habits of the buyer.

If your car is a high mileage car, the differential may have been changed out, or even have been rtebuilt with a different ratio gear set, so the stamp on the bottom web of the banjo cannot be trusted to be reliable. Still, it is a good starting place to determine your ratio. You will find two numbers there, which is the number of teeth on the ring gear, and on the pinion gear. Divide the large number by the small number, and you will have the ratio.

An easy way to check ratio is to put your car on a flat surface with a rear wheel valve stem directly down toward the road, put it in high gear, a piece of tape on the top of the crankshaft pulley. push the car straight ahead until the rear wheel turns exactly twice around. The tape on the pulley will indicate very close to 1/2, or to 3/4 around, which would indicate 3.54 or 3.78 respectively. There are other possible ratios, but these are the most common for your car.

Alan


37 Coupe    -- 09-18-2011 @ 4:07 PM
  The 1946 Ford was different in the fact that the standard ratio was 3:54,if you have an original 1946 Ford or Mercury owners manual you will see this on the specification page, I do not know about the 47 and 48 and don't know why Ford chose to do this after the war,fuel supply worries? or a surplus of the 3:54 but I do know that is what the majority of 46 Fords were supplied with and the 3:78 was an option that had to be ordered that way.


Steves46    -- 09-19-2011 @ 5:00 AM
  Ok, time to make my eye exam appointment! I have the owner's manual and managed to miss that! Thanks to all for their inputs. Steve


supereal    -- 09-19-2011 @ 9:13 AM
  I can't find anything that says that the 3-54 was standard in '46. Maybe I missed it somewhere. The two primary passenger car ratios produced from '42 thru '48 were 3-78 and 3-54. Finding a 3-54 today is fairly rare, at least here in the midwest. I suspect that a 3-54 in hilly country would have been a problem, unless you liked running in second gear. There has been a trend toward 3-54 lately, hopefully to improve fuel mileage. Usually it doesn't justify the cost and time. I suspect that the 3-54 may have been more common in the six cylinder cars, as they had considerably more low end torque than the eight. Henry forbade the advertising of the actual horsepower and torque of the six so it didn't eclipse his cherished V8.


37 Coupe    -- 09-19-2011 @ 9:42 AM
  Aside from 1946 Ford owners manual showing the 3:54 as standard rear axle ratio I have an original not reprinted 1946 Ford service manual 3606-46 August 15,1946 page 18.Rear axle : Passenger cars Ford (8-cylinder)and Mercury 3.54 to 1. Ford (6 cylinder) 3.78 to 1. Optional ratios available. Personally I have had three 1946 Fords and I have never seen a gear ratio other than the 3:54 in them or any 1946 Ford rear axles I have inspected.


ford38v8    -- 09-19-2011 @ 10:31 AM
  Wow. Never to old to learn something new. thanks for that!

Alan


37 Coupe    -- 09-19-2011 @ 11:32 AM
  There was also a good article on this in a past V8 Times,may have been written by Ron Love or McCoppin about the new 1946 Fords and new owners wondering what had happened to the Fords takeoff or acceleration from stop light. As usual I cannot find the article either in the printed index or the searchable one on this site,may have been late seventies or early eighties,could spend all day searching but got to get to garage. I remember another article which naturally I cannot find about Benson Ford I believe or whoever was head of Lincoln Mercury after the war. Anyway he was beaten at a street light by same year Ford,he was driving a post war Mercury,it was explained to him that his Mercury was a tad heavier than the Ford with the same horsepower (59AB but wouldn't you think he would have known?) anyway that led to the 4" crank as he demanded the Merc should be faster than a Ford as before war. Mayby one of those "urban myths"


EFV-8 Club Forum : https://www.earlyfordv8.org/forum
Topic: https://www.earlyfordv8.org/forum/viewmessages.cfm?Forum=18&Topic=3767