I just bought a 9 in Ford rear end for my 31 olds 5 window. The origial 8in Ford looked a liitle worn. I counted the gear ratio in the third member and after doing the math, (i had to take off my sandles and count my toes) if found out I have a 245 to 1 . It may have been taken off a high way crusin old lincoln. I am runnig a Chebby 350 with a turbo 350 automatic. I have a 3 deuce set up which looks "lights out". I figure she will have about 325 horsepower when I am done. I would like to cruice at 70 mph and not be redlining and losing my hearing . Should I put in a 373 gear and be done with it? Will I be able to spin the tires if I leave it alone? As you can all see, I am a dumb ass and this is my first car. Please try to treat me a little better then that dumb ass who bought a 64 Chevy Econoline without looking it over and was supriesed there was a 3 inch hole in the engine block. Regards:
you should be able to spin the tiresm, even with that high of a ratio, but i would suggest going to a lower gear for more around town fun
3.73 is pushing it a bit for highway cruising unless you have pretty tall tires.You can do it but you will be over 3000 at 70 not really cruise freindly rpms. I have 1 car w/3.73 gears but my other car has 3.42's which are a much better all around gear IMO
The size of your rear tires will have a lot to do with what works and what doesn't. Shorter tires give you an effectively lower gear ratio. Try it like it is first. You can change the gears any time later, if it's too high a ratio. One thing's for certain, with a 2.45 it'll do a hell of a burnout. Wheel speed will be WAY up there.
probably 2.47 ratio, that's what was available. Those gears would be real nice if you plan on driving 80 on the highway for extended times. 3.00 would be a bit more "normal" as a highway gear. 3.25-3.50 would be good for town/highway driving, and 3.70 would be good for in town and limited highway use.
If your just running a trans w/ a 1to1 final gear ratio and you want something that works good as an all around ratio and you have a rear tire around 27 inch tall I would run w/ 3.42 or 3.55 ratio. Has worked great in vehicles for me in the past.
If you are building a hiboy, you will probably have a rear tire about 30 inches tall. That makes your calculation easy: The engine speed at 90 is the just about the same as the gear ratio. For your 2.47 gear, that means about 2500 rpm at 90. For a 3.55 gear, about 3600; translates to 3000 at 75. Even with the tall tire, a 3.90 gear will buzz the motor on the highway. Turns out I have some personal experience with that one......
that's what 700R4s were made for...deep rear gears for around town fun and highway cruising. you can't have both, unless you have one
If you can do it The 700R4 is a great trans.The ratio are 1st 3.06 2nd 1.63 3rd 1.00 4th .70 30 Per cent reduction in your final drive and great 1st and 2nd gear. Here the info on the 300 1st 2.52 2nd 1.52 3rd 1.00. I have one in my 55 which I have a 383 with about 400 h.P. and had no problems. Drive it on the street and I do beat on it. Acechev55
Drive a car on a trip one time equiped with an overdrive, you will never be without one again. A 3:73 and a 700R4 is a good combination.
Here's Richmond Gear's gear calculation page. Just type in your gear specs, tire height and mph & it'll tell you what RPM you'll be turning. http://www.richmondgear.com/101032.html Hope that helps.
lessee, i went from a 350turdo to a 400 then a 700 and now it's getting a REAL 4 speed. you know, the ones that need a clutch.... and 4.10's.....
If you stay with the turbo 350, I agree with rocsoe - the 3.42 - 3.55 ratios will be a good all round gear. If you do go with an OD, then the 3.73 with the 700R4 or 4.11-4.56 with a real stick will be killer.
you already own the high gear try it you might like it . my opinion for what its worth is way to many guys are running to low a gear.
Just get it together and put some miles on it before you start ripping it apart. There are a lot of stalled projects out there because of to many changes before it even gets put together.
Wow, I'm surprised at the difference the 700R4 makes. I was playing around with this calculator and according to the calculator my 51 with 28.5 tire would cruise on the highway at roughly 2600 RPM going 70mph with 3.25 gears and 350TH trans... It would cruise at almost the same RPM with 4.56 gears with a 700R4..Thats surprised me...Does that sound right? Thats crazy I figured this with the 1.0 3rd gear of the 350TH and .70 overdrive in the 700R4
Yep, basic math says a 4.11 will be about 3/4 the rpm with a .70 overdrive so it'd be like cruising a 3.25 gear but give you the gusto of the higher RPMs in the other gears. I have to agree that you could put it together and then decide what you want to do. If you spend as much time as I do deciding, well, you may never decide! Good luck
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