rear end ratio to make happy rpms at freeway speeds

[moparmat2000]

Hi y'all

I have some gearing questions for you. I have an A-833 overdrive transmission im putting in my cuda. Im also slowly collecting the parts to shorten and rebuild an 8.75 rear for this car. I would like to get a ring and pinion that would allow me to have fun with the car in the lower gears , but allow the engine to run around 2300 to 2500 rpm in top gear at 70 mph. I will b running a 15" wheel with low profile tires diameter to be determined at this time. I was thinking either 3.55, 3.73, or 3.90 gears. I only am asking this as i want to buy one set of gears, and have the diff set up one time.

Anybody here have any facts on this one,

Thanks
Matt

 

[abodyjoe]

you need the tire dia. before you determine proper gear ratio.

 

[abodyjoe]

here play around with this calculator to find what works for you.

http://www.bigblockdart.com/forum/speedtire.php




.

 

[67Dart273]

Not gonna happen with any of the ratios you listed assuming a "low profile" tire. Back when I had the 70 440-6 RR, 3.54 with G60 x 15's gave up 3K at 70. Those tires show up as 26.4" dia

According to Joe's link, that combo is only 66.6 mph at 3K, so either my memory is off or the tire chart I found is a little off.

He's right though, you MUST know the tire size you are going to run.

You may be a candidate for an OD 4 speed.

 

[OldmanRick]

Hi y'all

I have some gearing questions for you. I have an A-833 overdrive transmission im putting in my cuda.

Del, that's what he asked about.

 

[67Dart273]

Del, that's what he asked about.

Oh hell I missed that!!!

Still need to know tire size, LOL

 

[Woods74]

This one is sweet too, uses a tick-tock-tach interface.

http://vexer.com/automotive-tools/speed-rpm-calculator


Broad sweeping general gear with no OD? 3.23.

 

[abodyjoe]

looks like with a 26" tire and a 3.55 gear you'll be about 2500rpm at 75mph.

26" tire and 3.73 gear will put you at 71mph at 2500 rpm..

 

[OldmanRick]

Oh hell I missed that!!!

. LOL.....Don't feel bad, i've done it more then i can count .

I was over at the other thread...lol. He ought to be able to figure out something with two.

 

[74DartSwinger360]

My Dads 68 Charger with 275-60-15 3.23 Sure Grip spins 2800 Rpm at 70Mph

 

[moparmat2000]

Yeah i clicked on it twice by mistake. Im out of town on business, using my android phone. Cant wait to mess around with the program from bigblockdart.com that Abodyjoe turned me onto.
Thanks guys

 

[dodge71demon]

I do not know if everyone caught that he is using the A833 OD.I do not know how much fun it will be in the lower gears.Not much IMO.The ratio is 1st 3:09 2nd 1:67 3rd 1:1 OD .73:1.Huge drop from 1st to 2nd.These were designed strickly to try and get a little better gas miliage out of existing motors etc.Remember the gas crunch in the 70's I do.I will be using the OD in my project car with a 318 the 8 1/4 I have has 2:94's but I may change to 3:55.But this car is strickly ment to be a good looking long hauler and I hate automatics