Topic: Change rear end gears??


ibshane    -- 10-29-2022 @ 3:11 AM
  I have a bone stock '37 Model 78 Deluxe Fordor V8-85. __Unfortunately it did not come with the Columbia 2-speed rear diff.

Any suggestions on possibly changing my rear end gears? The stock tranny gears seem to be pretty tall..., so I would think I could get away with putting taller gears in the rear end to get me humming up around 65-70 or so? Currently it really hums along at 50 mph, but any faster than that it's really winding out!


trjford8    -- 10-29-2022 @ 7:35 AM
  First you need to know what gears you currently have. check the bottom rib of the rear end housing and look for two numbers. Divide the small number into the big number. Also what brakes do you have? if mechanical I would not think you should be traveling at 65 or 70.


carcrazy    -- 10-29-2022 @ 1:35 PM
  The standard gear ratio for the 1937 Ford equipped with the 85 HP engine was 3:78:1, optional ratios were 4.11:1 and 3.54. The most common rear axle ratio for '37 Fords equipped with the 60 HP engine was 4.44:1. A 4.55:1 ratio was optionally available.

If your car still has the stock type of steering, brakes, shocks and suspension, a cruising speed of 50 to 55 MPH is probably best. With taller gears the car will go faster than that but the rest of the car is not up to the increased speed and you will find that you are overdriving the rest of the vehicle's capabilities.


ibshane    -- 10-29-2022 @ 2:02 PM
  Mine was converted to juice brakes somewhere along the line, possibly when it was restored in 2001? When I got it in 2016, I did a series of emergency stops with it testing the brakes and response time/distance.., as I do with every vehicle new to me.., and it performed surprisingly well. All else is stock '37


ford38v8    -- 10-29-2022 @ 2:34 PM
  As advised above, you may confirm the existing axle ratio on the bottom of the banjo to be the expected 3.78 to 1 ratio. As for humming along at 65 - 70, you can be confident that you will not over rev your engine, as it will float the points well before redline, thus limiting the revs. This is not to say that it would be safe to drive at that speed, only that it is possible without damage due to over revving.

Alan


JayChicago    -- 10-30-2022 @ 8:07 AM
  Do you enjoy driving your car? Why be in a hurry? Drive the Interstate in the right lane at 50-55. Wave back at the smiling faces passing you, admiring your beautiful old car.


37RAGTOPMAN    -- 10-30-2022 @ 9:12 AM
  IF YOU NEED to change your rear end ratio,
EARLY FORF V8 SALES INC
has the parts, I did this about 10 years ago, and should have done it sooner,
you will need to change the speedometer drive, so SPEEDOMETER reads correctly
WWW.EARLYFORD.COM
hope this helps, 37Ragtopman


MG    -- 10-30-2022 @ 12:25 PM
  If you find that the current ratio you have is 3.78:1, stick with it. I think it is the best all-around ratio. I regret having changed from 4.11:1 to 3.54:1 in my '34.
I found the 3.54 to be too tall on hills. If I had it to do all over again I would have replace the 4.11 with 3.78...


FordFreak    -- 10-30-2022 @ 1:58 PM
  My'37 coupe w/stock 85 hp. engine had 4:11's when I got it. With 27in. tall rear tires I was buzzing the engine a bit over 3000 rpm doing 52-54 mph. I had a 3:78 rear end laying around so I put that in it . Only droped a couple hundered rpm's. A friend said you will have to go to 3;54's to make a notable difference. I took his advice and changed to 3:54's. Best move I ever made! No problem on hills. Now, @ 3000 rpm's I am doing 65-67mph. I seldom go that fast, but it sure is nice just knowing that I can! The cars "sweet spot"is 2500 rpm's, doing 55-57 mph.
I do have juice brakes, and heave upgraded the front's to F100 "self energizing" Bendix type.
I got my gear set & rear axle rebuild parts from Mac VanPelt. Good quality parts & great service to boot! - F F

1937 Ford Coupe
1952 Ford F1 Pickup
1965 Falcon Sprint


Steve Kennedy    -- 10-31-2022 @ 12:33 PM
  I have a '36 5-window, with a 3.54 rear end. I (Bernie and I) put a Columbia in. At about 2100 rpm I am going 65. I'd go faster but I think I need to get the front wheels rebalanced. Anyway, I needed a 4th gear, now I have one.
Steve in Denver


kubes40    -- 10-31-2022 @ 2:17 PM
  65 / 70? Um, how do you plan on stopping before ramming into the BMW that just cut you off and hit his brakes?

Mike "Kube" Kubarth


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