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Discussion Topic:
Rear axle change
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shogun1940 |
04-13-2017 @ 10:51 AM
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Member
Posts: 464
Joined: Feb 2010
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I put an 8" Granada rear in my 40 ford,, 3:25 gear was to high .there are only to gear ratios that i found from. Getz gear 3:90 and 4:11 which i bought. A little to low. If you measure your tire diameter and add 1" of diameter it changes the gear ratio by one point. 4:00 too 3:90 for each inch of diameter. I would take the advice about driving the car for awhile and borrow some bigger tires to get the feel of a higher gear ratio.
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len47merc |
04-12-2017 @ 7:11 PM
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Senior
Posts: 1165
Joined: Oct 2013
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x3, 4 or 5 to wait a while and drive it. Considerations: 1) If typically around town and on the road or where you intend to drive is it typically flat land, hilly or foothills/mountainous? If anything other than flat you will not enjoy a higher gear, 2) Research the designed rpm for maximum torque for your engine - likely 2,500+/- rpm or so, and 3) Based on the tire size you are running, determine what highway speed equates to your optimum rpm (temporarily rig a dwell/tach meter - easy to do - and lay it on the seat/have someone read it). As noted earlier these cars weren't designed for 70 or 80. I found on my stock '47 59AB running a 3.78 gear and 710 bias plys that at 55 mph on the speedo, actual GPS speed is 60 and rpms are ~2,500 (optimum torque). Very torquey at this speed and comfortable - if I want to kick it up to pass, which is rare, it will go to 65 or 70 relatively easily and the car can still negotiate hills and the mountains without straining. '47 is not '51 I know but I just do not feel safe and comfortable driving the car beyond 60 mph and typically stay between 55 and 60 to fully enjoy the ride. For me personally I cannot comprehend the need to go above 60 with these EFV8s. I try to stay on the 2 lanes anyway which makes for a much more interesting drive. Tend to see and experience things and people I'd otherwise miss. Plus with all original glass I also try to avoid the typical road debris seen on the interstates. If you absolutely must do it IMHO an overdrive with an ~3.78 gear is the optimum set-up for all-around performance. Fwiw. If I want to burn up the road the G35 or my son's supercharged 250+ hp 1,800 lb Miata are more than adequate to kill me proper. Don't relish having to make any required quick, evasive maneuvers with the '47 above 55 - just darned dangerous, even with a fully restored suspension system in peak as-new condition. Steve
This message was edited by len47merc on 4-13-17 @ 4:49 AM
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1934 Ford |
04-12-2017 @ 6:11 PM
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Senior
Posts: 578
Joined: Oct 2009
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TomO is right to wait awhile. You will find all the 1951 parts were made for 50-60 MPH, not 70-80. Then if you want the engine to work less hard to do 50-60, just change the differential gears. At today's speeds, you'll beat your car up to keep up.
1934 Ford's since 1972
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carcrazy |
04-12-2017 @ 6:09 PM
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Senior
Posts: 1682
Joined: Oct 2009
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Here is an article from Hemmings about the Ford 8" rear axle. It is a great axle to use but requires some work to install. You can get almost any axle ratio you want in an 8" unit. https://www.hemmings.com/magazine/mus/2008/05/Ford-8-in--differential-carriers/1626174.html
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TomO |
04-12-2017 @ 7:06 AM
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Senior
Posts: 7264
Joined: Oct 2009
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If you just purchased the car, you should probably wait until you have driven it for a few thousand miles, before changing the axle ratio. The stock axle ratio is a good compromise for both city and highway driving. You may find out that it will suit you and no changes are necessary. If you intend to do a lot of highway driving, then I would suggest the overdrive transmission and a rear end ratio change.
Tom
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39 Ken |
04-12-2017 @ 4:59 AM
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Member
Posts: 380
Joined: Oct 2009
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Why not find an '51 overdrive transmission? It is a direct change out and all you have to add is a relay, a step down switch and wiring. If not included with the overdrive trans, you will also need a solenoid and a governor. Your car probably has a 3.73 rear end ratio and in overdrive that would give you a 30% reduction in RPM's. This is what I have in my '51 and we can travel on the Interstate with no problem.
This message was edited by 39 Ken on 4-12-17 @ 5:03 AM
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woodiewagon46 |
04-12-2017 @ 4:55 AM
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Senior
Posts: 705
Joined: Nov 2012
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I agree with Charlie. Why go into all the modifications needed to replace the entire rear, when any good gear shop can replace the gears in the center section and you can be on your way. What new gear ratio are you looking for and what is the current ratio?
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GK1918 |
04-12-2017 @ 3:15 AM
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New Member
Posts: 128
Joined: Aug 2016
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Just a note on Mavrick or its twin Mercury axles. Most are automatics and that won't work cause the ratios are in the two's. For this you will have to find a "hard to find one from a standard" I did this with a 1936 Plymouth which was a easy swap but was from a automatic oh ya, most driving was done in second at 65 mph and third I could do a scary 80, BUT taking off in 1st was pretty much gutless or worth less. So with luck my cousin has a 32 Ford hotrod 302 with automatic but he has a Mavrick standard axle so we swapped mine for his and we were all happy. Just find a overdrive trans. they are out there just keep looking sam
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CharlieStephens |
04-11-2017 @ 7:06 PM
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Senior
Posts: 894
Joined: Oct 2009
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Ask around and you will be surprised how easy it is the change the center section on a '51. You should be able to get a complete adjusted center section shipped to you from a rebuilder. Charlie Stephens
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deluxe40 |
04-11-2017 @ 7:00 PM
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Member
Posts: 413
Joined: Oct 2009
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I would have questions about all of the places the rear axle meets other components: springs, shocks, driveshaft and wheels. Ford introduced the automatic transmission in '51 so you should be able to find a center section with a 3.31 gear ratio that will fit your axle. Try shoebox-central.com .
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