I have been working on my roadrunner for several years and have finally gotten her to a place where I can drive her. There are a few small issues I need to address, one being the gearing in the transmission. I had done a lot of research when I was building the car and decided on 4:10 gears in the rear with a late model A833 with overdrive (which came with the car)…the one where they flipped the shifter linkage. It has a weak OD gear I read, but I thought I’d only use it on the freeway and it would allow me to cruise 2,500 rpm at 70 mph.

I THOUGHT I knew what the gear ratios were in the transmission based on what I’d read. I am going ~55 mph at 2,500 rpm in fourth gear. I am not sure what the ratios are in the transmission but it pulls like a monster!! What would be the best course of action to have freeway drive ability and still have some acceleration from a stop? I’ve attached some ratios…should I change the rear end? Based on what I’ve observed while driving the speed to rpm matches the 4:55s based on the ratio calculator. I’ve checked and it is a 4:10 (turned the wheels on a lift). The 4:10 ratio calculator results are what I’d like to have/was hoping for. Advice and questions welcomed. Thanks!

Edit: What other ratios were there in the overdrive A833s? I think the ratios I researched are not correct (obviously!).

the 3.09 1st gear is the steepest in any version of A833.

You need to run the commonly available rear gear ratios thru that calculator and see which one gives you the desired RPM at 70. 3.91 or maybe 3.55m assuming something other than a Dana.

Sniper - I’m not sure what the ratios are in my transmission…I know it’s the version with a flipped shift linkage and that’s about all. I’m curious to know what the ratios might be so I can figure out what gear ratio would be ideal for the rear end.

Edit: I found this on allpar, not sure if there were more options/combinations out there.

Edit 2: this may be what I have…the 74-75 ratios. It isn’t overdrive but I’m not sure how that worked, if all the later transmissions used the flipped linkage. Hmmm.

Only one transmission used the flipped lever, the A8833OD.

What is the loaded tire radius on your car?

Measure from the ground to the center of the axle shaft and let us know.

FWIW, There are 2 OD gear ratios for that transmission, and the speed gears and counter gear are NOT interchangeable. The gear sets have different pitches. The common Dodge/Plymouth A833OD has a final gear ratio of .73:1. The other version has a final gear ratio of .71:1 (if memory is correct),........or maybe it was .69:1..........Hmmmmm?

I put one in my RR with 4.88s.

I keep hearing this but never see proof. Why would Chrysler make a different set of gears for an infinitesimal difference in ratio?

I will admit though, my my OD era parts manuals are thin.

They were also sold to GM for use in trucks.

You can verify the ratios with the tranny out of the car or in the car by marking the front driveshaft yoke and the tail shaft housing and having the rear wheels off the ground, remove all the spark plugs and have someone rotate the crankshaft one full rotation with the tranny in the O.D. gear and count the driveshaft revolutions. It should rotate one full revolution and right at 10% (.09) more
You can verify any gear ratio by using this method, same thing on the rear end ratio, turn the wheels one full revolution with a posi and count the number of pinion yoke revolutions, if the yoke turns 4 and a little bit more it is 4.10, if it rotates 4 and 1/3 it is a 4.30 ratio, if 3 1/4 it is a 3.23 ratio and so on

Transman - I won’t be able to measure it for a month and a half as I’m away at work. I will measure when I get home…

Cab_burgh - thanks for the info, we tried part of that to verify it was a 4:10 differential gear.