| croftonfoxes | -- 05-20-2019 @ 8:37 AM |
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Hello Everyone, I have a dilemma that I need some help with. My '48 Convertible drives just fine at 50 to 55 mph, and can probably go all day. However, at 60 it is getting a irritated and at 65 it is down right out not happy. It will do 65, but I am pushing it and I do not want to. It would be very nice if the car cold be happy at 65 so that I could drive it on the highways near us (Annapolis/DC area) to go to some events and car shows a little further. My dilemma is do I go with a taller gear in the rear end, and sacrifice some low end performance, or do I pony up and commit to a Mitch*ll OD? A Columbia 2 Speed is out of the question due to cost and availability. I have read good things on the Mitch*lls, but being that the '48's never had OD offered on them, I am a bit skittish to heavily modify my drive train to accommodate a Mitch*ll. Therefore I am leaning more towards a a taller rear end gear... Nothing crazy, maybe just a 3.25 or a 3.54.. Thoughts? This message was edited by croftonfoxes on 5-20-19 @ 8:39 AM
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| len47merc | -- 05-20-2019 @ 10:06 AM |
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For your vehicle, your area, and best all-around performance stay with (what is assumed here based on your description) your 3.78. 3.54s are not the best in hilly areas for stock flatheads but mid-western Flatlanders love them. I routinely drove my '47 with 3.78 up and down the east coast including your area and Appalachians and it worked fine - I just always avoided the interstates in favor of 2 lanes and 60 mph max (measured via GPS - speedometer read 56 mph). Quite frankly this era of cars were not designed to drive any faster than this and are not safe IMHO above 60 mph actual on stock suspensions especially in the event of any needed emergency maneuver at speed. Slow down, smell the roses, be safer and find the best holes in the walls and true USofA on the 2 lanes and save yourself $$$'s in the process. EDIT - If you ultimately feel the need to turn 1,850-2,100 rpm at 65 mph (again measured via GPS, not your speedometer) then I'd recommend the overdrive route over changing your rear gear. That 3.78 works great around (hilly) town with plenty torque and zip and as well gives you plenty of torque in the mountains (relatively speaking flathead-wise) - 3.54 not as much excepting for all flat-land. I do not think it even close to going out on a limb to say you will be quite sorely disappointed with a 3.25. Nice car btw! Steve This message was edited by len47merc on 5-20-19 @ 12:59 PM
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| CharlieStephens | -- 05-20-2019 @ 10:06 AM |
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What is your current gear ratio? Charlie Stephens
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| croftonfoxes | -- 05-21-2019 @ 11:38 AM |
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Thank you len47merc. I had completely not considered hills with a taller rear end, and we do have some good sized hills around my area. Thank you for pointing that out! You are also very correct about what is essentially a beefed up Model T suspension that is slung under my '48... Yes, it is probably best to leave the car the way Henry intended and just enjoy the slow lanes! Thank you also for the kind words on the car too!
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| supereal | -- 05-21-2019 @ 11:41 AM |
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I have a 3:78 rear end in my '47 convertible. Living two miles from an Interstate, I needed to be able to merge at or near the speed of the traffic. After long consideration, I chose an overdrive unit. It is a Ryan, and I am not sure they are still in business, as I bought it nearly 20 years ago. I chose the 30 percent gearing, and it allows me to run as fast as I feel safe with a 75 year old car. The drawback is that the unit has to be locked out below 40 mph, such as at in-town driving. At those speeds it lugs the engine down too far. I use a truck type PTO cable to shift it. I had to devise a way to connect to the unit, but it is convenient to shift a needed. The 3:78 was chosen originally at the factory to put the engine speed for the highway where it generated the best rpm for power and economy at the prevalent 55-to 60 range. Changing ratios by re-gearing will create power problems at one end or the other between power at low speeds and being able to keep up on the highway. An overdrive lets you select the best ration for the circumstance. I have no experience with the Mitchel units, but what I have heard is complimentary.
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| croftonfoxes | -- 05-21-2019 @ 11:42 AM |
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Charlie, I am not 100% certain, but it is supposed to be 3:78. By the way the car performs, I would say that would be a better than even bet.
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| wmsteed | -- 05-22-2019 @ 8:47 AM |
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I generally agree with the comments about going to a higher speed ratio and i am not a big fan of the aftermarket OD's which require cutting the drive line. My 36 had a Columbia under it when I bought the car in 1952. Never had any problem with it other than the fact that is was not user friendly, shifting was a little crude. In 1956 I upgraded the rear end to a '47-48 Columbia, keeping the original banjo/drive-line. (3.78.1 ratio). The shifting on the 42-48 Columbia is very simple, electric over vacuum . The unit is trouble free, very user friendly, my late wife drove the car on a regular basis, and there is no modifications required to the chassis, etc. Bill 36 5 win delx cpe
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| 37RAGTOPMAN | -- 05-22-2019 @ 11:25 AM |
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I installed a 354 ratio in my 37 85 hp CABRIOLET and drove from MAINE to NEW YORK STATE, NATIONAL V8 FORD MEET, I went though NEW HAMPSHIRE and VERMONT, with no issues, went over many hills, bought all new parts from the V8 FORD SALES, advertise in the V8 TIMES, hope this helps, 37RAGTOPMAN overdrives are ok but remember you get little or no help from the engine to help you slow you down,
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| croftonfoxes | -- 05-23-2019 @ 11:22 AM |
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Wow! Thank you all very much! You have given me a lot to think about! Thank you again!
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| supereal | -- 05-23-2019 @ 1:50 PM |
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With my Ryan unit, it was furnished with a new torque tube and driveshaft. It coupled directly to the pinion on the rear axle. The OD unit has a place to connect the speedometer. The only problem , initially, was with the internal torque tube bronze bushing that supports the new driveshaft. Until it was run for awhile, the grease fitting on the torque tube required frequent pumps of lube. After that it was no problem. I liked the unit because it was bolted directly to the axle, and others hung the unit in the center of the torque tube. I looked for a Columbia, but only found junk. Without the controls and speedometer shifter, etc., the cost to replace these parts made the investment too high, even if the axle internals were acceptable. When the Columbias were removed, the salvage yards seldom took time to remove and save the everything other than the axle itself. I am not a purist, but restored my '47 convertible to be a reliable driver, where the fun is.
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