What kind of rear end do I have?

[Confederate1969]

In any other setting a man could never ask such a question, but in the garage it's perfectly legitimate for grown men to ask each other about their rear ends. :jester: So on the topic of rear ends, where would I look for numbers to know what kind I have? I'm sure it's some lousy road gear but I'd like to hope for better.

With that being said, if the one I have is no good, or I just plain don't like it after seeing it, how much does a new rear end cost? Even if it's some outlandish price, I'm interested what that would cost to do such an upgrade.

 

[Basketcase]

your car should have an 8 3/4. pretty much indestructable. Most likey your ratio is 3.23 or maybe 3.55.There should be a metal tag on one of the center bolts, but more likely it's gone. On the side of the center, there will be a 489 or 742. IIRC, the 489 is more desirable, but both are good. My first '69 had 3.91s. The car that burned in my fire had 3.55s. The 3.23s are good all around. somewhat snappy with the 440 I had, but the 3.55s are even better. The 3.91s are good performance wise, but on the road doing 60, the engine will sound wound out, and they're hard on gas.
I'd like to have steeper gears in mine, but this summer with $4 a gallon gas, I was still able to dive mine almost everyday to work, and it was alot cheaper than my old 4x4.
as far as cost for new, I've never had to replace a Chrysler 8 3/4. Used centers, espically Sure Grips can go for $600 and up at the shows, but like with any paart, do some shopping, and find a good deal. Chrysler put the 8 3/4 in thousands of cars and trucks from the '60s to the 'late '70s.

 

[Big John]

If the tag is gone, or you want to make sure what it is, jack up the rear of the car and with the car in gear (or park) and emergency brake off, grab one tire and see if it turns. If it doesn't, its a sure grip. If the tire spins and the one on the other side spins the opposite way, you have an open rear.

Next, mark the tire in one spot and slide under the car and mark the driveshaft. If you have an open rear, block one wheel from turning.

Spin one wheel one full turn while someone watches the driveshaft and counts the turns. If your driveshaft went 3 1/4 turns, you have a 3.23:1. 3 1/2 turns its a 3.54 etc. If you have an open rear, double the turns of the driveshaft. ex. 6 1/2 turns is a 3.23:1 ratio.

 

[Hoosier Bird]

Very well put, John..........

 

[Plymouthfan]

I had a 741 open end 2.97 when I bought my car but added a 489 3.55 sure grip a few years ago.

 

[Roadcuda]

My car had a 489 case with 3.91s sure grip when I got it. As Dave said, those make the engine scream when at highway speed. Since I wanted to be able to drive my car I found a complete 489 case with 3.23s on ebag for $200. I also had someone interested in my 3.91s and sold them for, $200, so that worked out real well. The switch really just cost me the shipping charge.

 

[6t9runner440]

mine had a 323 open rear and now has a 489 case set of 355's...only thing i had to do was change the yoke too....might want to keep that in mind

 

[Basketcase]

or they make a combination U Joit for the smaller yokes. I had one on Freebird. Hammered on it, no problems.











"Dear Santa"

 

[droptop]

I don't think anyone here minds what it looks like as long as it doen't start making a lot of noise.

I think that all of the Road Runners in '69 came with the 489 case and the big yoke. 323 is about the best gear for driveability, but 391's sure are fun to drive.

 

[SomeCarGuy]

If it has no rear cover then it is an 8 3/4.

A 3.23 is a real good all around gear, and 3.55s are nice yet liveable.

Most of the guys that have tried a swap on the 3.23s to 3.91s at the track see a very smaller ET difference, maybe a tenth. Most cars that are close to stock won't see much ET gain from deep gears. If you are running some stepped up heads and cam package then you would likely see more gains.

 

[Plymouthfan]

If it has no rear cover then it is an 8 3/4.

A 3.23 is a real good all around gear, and 3.55s are nice yet liveable.

Most of the guys that have tried a swap on the 3.23s to 3.91s at the track see a very smaller ET difference, maybe a tenth. Most cars that are close to stock won't see much ET gain from deep gears. If you are running some stepped up heads and cam package then you would likely see more gains.

I gotta agree! My friend ran a best of 11.99 at our last track rental in a 69 Satellite with a 440, mild cam, torque converter and reverse manual valve body and still has 2.93's out back!!!!

Here's some good Mopar rear end info to look over, this should answer and questions and provide some insight.

http://www.geocities.com/MotorCity/Flat ... ndex3.html