| fortyford | -- 02-13-2016 @ 4:16 AM |
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How rare is 3.54 ratio rear ends in a 40 Ford.Were they maybe just put in 4-door cars?I have a 3.78 in my car now and was wondering if there would be quiet an improvement going to a 3.54 for highway speeds?Are they all marked on the bottom of the housing on the "flat" spot?
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| kubes40 | -- 02-13-2016 @ 8:24 AM |
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I've never stumbled upon any information that documented how many of each ratio were installed in 1940. I'd have to believe that a factory installed 3:54 in a Ford was an "oddity' much more so than a frequent occurrence. The best ratio for you depends on how you drive, how fast you drive and your traveled terrain. In the Midwest, I prefer a 3:78. Good for pulling away from a dead stop. Also good at climbing hills. Allows for a comfortable 60ish MPH. A 3:54 will allow you more top speed but will negate some of the "thrust" of pulling away from a dead stop. And, as far as top speed is concerned, in my humble opinion, anything over 60ish, well, remember your driving on 1940 technology. Even restored "as new" the brakes are not going to react well enough to avoid bouncing off that new Mercedes that just cut you off in traffic. And the steering? You're not likely to safely swerve out of his way. All differential housings were stamped with the gear ratio. Whether or not that's what is currently residing in your housing, well, maybe, maybe not. Mike "Kube" Kubarth
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| std1940 | -- 02-16-2016 @ 12:52 PM |
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53 years ago I as a foolish 16 year old I was able to get my 40 up to 100 mph. I will take it up to 80 mph now at least once a year.
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| len47merc | -- 02-16-2016 @ 5:35 PM |
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Agree with Mike and add only that if you drive predominantly, meaning most all the time, on flat terrain (as many mid-westerners do) then perhaps the 3.54 will work for you; otherwise the 3.78 does give you the best pep all around, particularly on rolling-to-hilly terrain and also keeps a typical flathead V8 in the sweet spot of the torque range (~2,500 rpm) at 60 mph. I personally find no need to or comfort (engine noise or handling) in driving above 60 mph and prefer to stay in the 55-60 mph range for max highway speeds. Also, if you are running tires above stock height with a 3.54 you will very likely note a further reduction in acceleration and performance - not nearly as evident with a 3.78. Steve This message was edited by len47merc on 2-16-16 @ 5:38 PM
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