REAR END GEAR RATIO- A100

I'm running about 2000 rpm at 55 mph with a Chevy 305 automatic in my '64 A-Pup. Wondering what the gear ratio of the stock rear end is-?-

Thanks-

assuming you don't have a OD trans and about 27" tire i would guess around 292

hastingsman wrote:I'm running about 2000 rpm at 55 mph with a Chevy 305 automatic in my '64 A-Pup. Wondering what the gear ratio of the stock rear end is-?-

Thanks-

   Try this site   https://tiresize.com/gear-ratio-calculator/          Ron

The stock rear end is 3.23, casting typically is 741 (on the driver side of the rear end, input shaft). But the casting does not tell you about the ratio.

There's plenty of information:

https://www.hemmings.com/magazine/mus/2004/10/Mopar-8-3-4-inch-rear-ends/1280934.html
http://www.moparwiki.com/index.php?title=Rear_Axle_8.75%22

THANKS MUCH!

The stock rear gear ration that came with your rig should be listed on the info plate riveted to the drivers side fender well beside the seat (mine says, 355 rear gearing on it).

There are some things to consider in adjusting your RPM, rear weel and tire size, manual vs auto trans, and rear gearing.

It's probably a 741 type rear chunk, there may or may not be a metal tag under one of the chunk bolts, mine didn't have a tag. The gear ration was stamped on the out edge of the ring gear and matched my info plate.

I got my van with 3:55 gears and 14" wheels with low profile tires (chicano low rider look), it was screaming at 55mph.

I swapped the rear gear to a 2:76 and left the 14" rims but went to a 235/70 tire, I have to run the gears out a little now before shifting but it pulls about 2200 at 65mph which is doable.

eta: There are some online calculators that figure gearing and rim/tire size to rpms/mph, thats a good start

That's what I've been after, the rear end number it was born with. Thanks for pointing out Chrysler's willingness to share info on an easy to locate plate.