741 742 or 489 sure grip

[70 Challenger Lover]

What gear ratio were you looking for? Someone in here might have a nice used setup with the correct 489 case so you could just drop it in.

[Arctoad]

I think its a 391, but again unless I can find the broadcast sheet somewhere in the car I'm sort of guessing..
Here's a question though;
Is there a chance that the Axle housing is original to the car? I know the leaf springs are, they have the correct part number which were unique to the T/A's AAR's. 
Thanks

[70 Challenger Lover]

I'm not sure if that's easily determined. Maybe someone in here can explain the differences. I assumed the housings were pretty much identical over the years. Odds are that it is the original housing. Changing the center pumpkin section is a piece of cake compared to the whole rear end so I can see some previous owner doing that, especially if the car once had 3:91 gears. I wouldn't last long with that gear set. I got tired of 3:55 after about 1000 miles of use.

[6bblgt]

I think its a 391, but again unless I can find the broadcast sheet somewhere in the car I'm sort of guessing..
.....

do you have the original transmission? 
a 3.91 T/A would have a 39 tooth GREEN speedo pinion &
a 3.55 T/A would have a 35 tooth ORANGE speedo pinion
originally if it hasn't been changed

[Arctoad]

Nope unfortunately A833 Trans is from a "B" body 68'
I've been reading a lot about the 8-3/4 and the differences between the pinions as well the "Sure grip" units, so looks like I'll need a 489 housing and ring and pinion but apparently the sure grips are interchangeable.. and depending on the year they can be rebuilt. not sure about driveshafts though..

[Arctoad]

I guess thats exactly what you said.. 

[70 Challenger Lover]

Nope unfortunately A833 Trans is from a "B" body 68'
I've been reading a lot about the 8-3/4 and the differences between the pinions as well the "Sure grip" units, so looks like I'll need a 489 housing and ring and pinion but apparently the sure grips are interchangeable.. and depending on the year they can be rebuilt. not sure about driveshafts though..

It sounds like you are trying to get the car back to as "correct" as possible. That means you should get a 489 case and it will need a ring and pinion designed for this case since the pinion shaft is larger than other cases. If "correctness" is the ultimate goal, you need to figure out two important things about your car...the gear ratio it came with and the build date of your car so you can get the proper date code on the 489 case. I would start with those things.

I was digging through my stuff and found a center section with the 489 case but it had 3:23 gears and an open center rather than limited slip. The date code was 2369 making it August 24, 1969. This would be the right date code for a car built sometime around November 1969. There is probably someone in here with exactly what you need at the right price but you need to decipher that build sheet so you know what ratio it came with.

[Arctoad]

Thats the goal but the real problem is no build sheet.. yet unless monkeys fly out of my !@#% and I find it somewhere in the car. I think your idea is exactly what I should do.
thanks

[70 Challenger Lover]

The fender tag will show the build date. The driver door jamb sticker will show the build month. Since no one can see what gear ratio you have inside, I'd go with a ratio you like best for your driving needs and build a 489 case with the right date code.

[Arctoad]

Cool suggestions much appreciated