Rear end gear options
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Junior User
Joined: Feb 2006
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Rear end gear options
I have decided to change out the rear end gears in my 1952 F1. The stock gears are 3.92. I have choices of 3.54 or 3.31. I have the stock 4 on the floor and the stock 16" rims and stock 215 CI engine. My question is which one of these two options would be best to still have out of the hole power in 2nd gear and have good highway speed,say 65 to 70mph with an RPM in the range of 2500. Thanks ,John
Fleet Owner
Joined: Jul 2004
Posts: 27,294
Likes: 1,055
From: NM
I guess my first question would be, are you going to lower the truck, put on sway bars, modern steering, and dual-circuit disc brakes? If not, would you really want to go 65 - 70 mph in one of these old trucks? Maybe if you are in west Texas or eastern NM!
There are seveeral gear ratio calculators on the web, I think there is one on here if you do a Search. You can put in your tire diameter, gear ratios, etc and it will spit out your RPM's.
There are seveeral gear ratio calculators on the web, I think there is one on here if you do a Search. You can put in your tire diameter, gear ratios, etc and it will spit out your RPM's.
If you use it, SUPPORT IT
Joined: Sep 2007
Posts: 1,595
Likes: 0
From: Indiana
Ross is right - without modern suspension, brakes, etc, the only time the truck should go 70 MPH is over the cliff....
Mine will be almost totally stock, except will have a new(er) rear end, with 3.73 gears instead of the 4.86 in the stock rear. Reasons? So I have bigger/better brakes, and my old flathead won't be turning a gazillion "R's" at 50 mph. I'll still go 50 maximum, even though I should be able to go faster. And 50 will probably be the exception instead of the rule - 45 is just fine, thank you, in an old truck. Someday I may decide to modernize it all, but for now, and the type of driving I have planned, the old stuff is ok. Now, someday I might have an F1, with new motor, etc...then I'll have discs, 4-link, etc. But, one truck at a time...
R
Mine will be almost totally stock, except will have a new(er) rear end, with 3.73 gears instead of the 4.86 in the stock rear. Reasons? So I have bigger/better brakes, and my old flathead won't be turning a gazillion "R's" at 50 mph. I'll still go 50 maximum, even though I should be able to go faster. And 50 will probably be the exception instead of the rule - 45 is just fine, thank you, in an old truck. Someday I may decide to modernize it all, but for now, and the type of driving I have planned, the old stuff is ok. Now, someday I might have an F1, with new motor, etc...then I'll have discs, 4-link, etc. But, one truck at a time...
R
Super Moderator
Joined: Apr 2004
Posts: 34,494
Likes: 2,809
Calculator is here:
Novak Conversions - Gearing & Gearing Math for Jeeps
Your current set up, assuming 30" tires, will have you spinning 2854 rpm at 65, 3074 at 70.
3.54s: 65 = 2577, 70 = 2775
3.31s: 65 = 2410. 70 = 2595
Drive as fast as you like.
Novak Conversions - Gearing & Gearing Math for Jeeps
Your current set up, assuming 30" tires, will have you spinning 2854 rpm at 65, 3074 at 70.
3.54s: 65 = 2577, 70 = 2775
3.31s: 65 = 2410. 70 = 2595
Drive as fast as you like.
