Finally found out what my read end ratio is & why I have poor acceleration.
Took off the cover this weekend and counted the teeth.
Pinion = 17, ring gear = 41; ratio = 2.40. Man that sux!!!
No wonder I have no power on acceleration. But I get good gas mileage on the road. Bet I waste a lot of gas trying to get up to speed though.
Think I'll go with a 3.53 rear gear set, hopefully posi.
A friend is going to give me a 10 bolt posi center section.Don't know yet what gears are in it.

check this site out, it has a good calculator to help with gear ratio/rpms conversion plus other calculators.

http://www.sh3d.com/ss/calculators.asp

rickd
--
project...39 ford pickup

Hey Fred,If you drive alot on the freeway you won't want a 3:53 gear. I think it is prefect for short runs and is great for in town. But if I did the freeway thing I would go to a 3:00 or near that.My truck has a 3:54
in it and the only time I would like a taller gear is on the freeway. Or if you have an overdrive I would go to a 4:10 for about the same results....Ray
--
Grump

Grumpy;
That won't give me much advantage over the 2:40 I have now will it? I admit the 2:40 is cool for the road trips, but it sure sux for gettin' going

Try 3:73 with 15" tire. The 283 should be able to make them bark. Although smoking tires is a good waste of HP. Acceleration and tire smoke are two different things. I had a Nova as a kid that I raced stop lights with, 327 @ 7000 rpm launch 3sp manual 85mph in a block little tire spin on 10" wide snow tires. Hell on rear ends, trans and clutchs.
Smarter now...Most of the time.
--
Mike J

You will be amazed at the difference. You'll think someone put in a new motor while you weren't looking,Lol
Go with a 3.50:to1 or there abouts if you want to see a real difference..
I would rather have a lower gear for all around hot rod driving myself...
--
Grump

Talk about freeway gears, i got 2.73 in mine with a 700r4 trans. Going 80 mph, i turn 1,500 rpm.
It was built to cruz the freeway.


Rick
--
awsum34

Remember the only dumb question is the one you don't ask.

No one has brought up the most logical alternative, and that is an 700R4 overdrive transmission. With that low first gear and the overdrive fourth gear, you can have the best of both worlds. I am going that way with my new car. Save you money and then do it right. For example, with my 30 inch rear tires, I can run a 3.89:1 rear gears and cruise at 2200 rpm in overdrive at 70 mph.
--
Lynn
'32 3W

rumrumm;
Yeah, that is the most logical solution for sure. If I was building the car right now I would do that.
It's not that I WANT to spin the tires all the time, it's that I couldn't figure out why I couldn't do it when I wanted to.

Just for numerical perspective if it helps any:
going from 2.40 to 3.00 is a change of 25%
and 2.40 to 3.50 is a change of 46%
If it were a manual tranny the rpm would rize by the same percent.

Playing with the Excel spreadsheet recently. Anyone know what the height of a 7.10 15 is?
Changed plans from a built C-4 to a 700R4 behind the blown 296 cube flatty in the T coupe. The goal is 2200 at 75mph. With that great low gear I should still be able to have fun with the kiddy cars at the lights.

--
Carl
Automotive gold is everywhere; you just have to learn how to dig for it

if i were to guess, a 7.10x15 should be about 26". this kind of tire sizing was not very dimension oriented and would vary in size from brand to brand, unlike the
p-numeric sizing where the dimesions are very close.without overdrive, a 26" tire at 75 mph will calclate to 2229 rpm, with a 2.3:1 ratio diff.
--
project...39 ford pickup

Fred, you might want to keep that gear combination if you ever want to run at Bonneville LOL With a 26 inch tire I would go with a 3:08 rear for decent all around operation. Course, that will depend on the vehicle weight too...
Fred P
--
Fred P.

Fred,
Your little 283 likes to rev. If you're running a fairly tall tire, and you do a 50/50 highway/around town split, I'd go with 3.08's. If you do mostly around town, with a freeway blast once in a while, I'd go with 3.42's or 3.55's.
If you're getting a later model 10 bolt, most 1/2 ton suburbans without a towing package had 3.42's. With towing package most were 3.73's. A hint from a cheap SOB!
I've been waiting for my 'burban to die, so I'll have 3.42's for the big Olds. That truck is like that damn bunny on TV, it keeps going and going and going! hehe
--
Charlie

Fred, Take a minute, go out and measure the overall height of your rear tire. Then go to www.ring-pinion.com and checkout the calculator section. Enter your trans. type, rear gear ratio, the height of your rear tire and your average cruising speed. It will calculate the exact rpm that you will be running at that speed. I found this very helpfull in my rear gear selection and its kinda fun to play around with. Now I have a very happy rat motor with a t-10 4 speed and 3:50 gears that the local kids with there Mustangs and Camaros have come to hate, but respect.
Hope this helps.

blksheep in Charlotte