Gears

[Hoosier Bird]

What rear end gears do you guys like for overall cruising and let's say 100 mile trips? My 292 cam does not like my 3.23. I hate my 4.56 if you have to go more than 2 miles. So, if you had 1 set to leave in all the time what would it be?

 

[69383RR]

How would one know what size gears he has .I know its a lame question but that's why I joined this forum. There is no tag or anything on the differential that identifies it .Any help would be appreciated .

 

[Roadcuda]

Gary, FWIW, my car has a stock engine with 3:23 gears and I like them for driving.
IIRC you can figure the gear ratio by jacking both rear wheels off the ground and turn one the the wheels one full turn while counting how many times the drive shaft turns. That should get you pretty close. If you had to pull out the case the ratio is stamped on the ring gear.

 

[droptop]

Jack up the rear wheels and turn the tire one full rotation while counting the drive shaft revolutions. 3.23 would be about 3 1/4 turns, 3.55 would be about 3 1/2 turns, 3.90 would be just about 4 turns, etc. With that cam, I would say 3.55.

 

[69383RR]

Thank you so much I'll get right at it .

 

[Big John]

How would one know what size gears he has .I know its a lame question but that's why I joined this forum. There is no tag or anything on the differential that identifies it .

You got lame questions?? We got a lot of very lame answers... and comments ... and jokes....

But seriously... jack up the rear of the car first. Mark a spot on the driveshaft and one on a tire. I assume you have a suregrip rear end. Turn the tire one complete turn and count the driveshaft revolutions. If the driveshaft turns 4 times for every revolution of the tire, the ratio is 4:1.

You have to use a little common sense on finding exactly what ratio you have. If the driveshaft revolves 3 1/2 times, it's a 3.55:1. 3 1/4 times is 3.23 and so on.

If you don't have suregrip you have to block one wheel and then divide the revolutions of the driveshaft by 2.

 

[Big John]

Jack up the rear wheels and turn the tire one full rotation while counting the drive shaft revolutions. 3.23 would be about 3 1/4 turns, 3.55 would be about 3 1/2 turns, 3.90 would be just about 4 turns, etc. With that cam, I would say 3.55.

You type faster than me!!

 

[4spd69RR]

I like 3:55, 3:73, and 3:91. I also have 4:56 gears installed presently and I'm thinking about replacing with 3:91's. Bad part about it trying to find someone local that has enough experience with the 489 case.
@ 69383, the size is stamp on the gear, Also there is a calculation; count the number of rotations of the wheel x the wheel size or something like that, I'm sure someone else will chim in.

 

[Basketcase]

I've always liked the 3.23s for all around. good milage, but still peppy. Freebird had 3.55s in it, and that car loved to cruise at 70. The car before that had 3.91, didn't like the highway.

 

[69383RR]

I don't get it , why are there so many different sizes . When the car came from the factory was there one all around size that the car came with ? Or are these different size gears installed after the fact by there owners ?
The reason I'm asking these lame questions now is because I don't want to look like a dumb ass when I'm in my car at some car show and someone asks me these questions . :loco:

 

[4spd69RR]

Most Road Runners came from the factory with 3:23 gearing, unless you order it special. Also remember back in those days Chrysler would build cars to order to be drag strip ready. The concept for the Road Runner was to be low cost, Mid size, 14 sec car.

 

[Hoosier Bird]

It's not actually a size but a ratio. Most of the ratios talked about came stock in our cars. It depended on the engine and tranny combination.

 

[Roof man]

Mine has 4:11 I'm changing to 3:55 for better drivability. Hope this helps.

 

[69383RR]

Most Road Runners came from the factory with 3:23 gearing, unless you order it special. Also remember back in those days Chrysler would build cars to order to be drag strip ready. The concept for the Road Runner was to be low cost, Mid size, 14 sec car.

I did not now that , very interesting bit of history info there !

 

[Basketcase]

no dumb questions here, we all had to learn sometime. the lower gears, 3.23 or lower, give lower rpms on the highway, better milage. 3,55 or say 3.91, you get better starting out, but higher rpms at say 60 mph.

 

[69383RR]

Mine has 4:11 I'm changing to 3:55 for better drivability. Hope this helps. View attachment 4256View attachment 4256

You have a very beautiful roadrunner , just beautiful !

 

[69hemibeep]

They had optional gears. 323 was a typical standard gear, my car is a trackpack 4spd so it had 355s limited slip then there was a super trackpack 410s with power disc brakes 373 and 391s were optional also depending on the car. I believe the A12 cars were 410 with drum brakes am I right guys?

 

[Big John]

They had optional gears. 323 was a typical standard gear, my car is a trackpack 4spd so it had 355s limited slip then there was a super trackpack 410s with power disc brakes 373 and 391s were optional also depending on the car. I believe the A12 cars were 410 with drum brakes am I right guys?

Yes, this time you are right....

 

[69hemibeep]

Yes, this time you are right....

:lmao:

 

[gunnar]

Great info. I never understood rear ends until now. I learn something every day on this site.