8-3/4 rearend in a 70 cuda

[copper01]

I am trying to locate some info to determine if the rearend in my car is possibly the factory installed?  Its a 70 cuda 340 built during the 7th month of 70 and it has a 742 housing. Were all 3 casting housings available at the same time? or is there info that I can locate on the housing that im not seeing? Thanks

[Rich G]

Don't know but I just took the rear out of my 70 challenger and it has a 742 case in it too. It has the matching 340 engine and trans and the rear looks like it's never been touched. I thought they all used the 489 case but I guess not. I have the build sheet but i don't know how to decode it or if it would indicate what case it has.

[70chall440]

Just got this off My Mopar

1-3/4" large stem pinion (aka. '742')
 Carrier casting numbers: 1634985 (1957-1964), 2070742 (~1961-1969). This assembly was replaced by a phase-in of the 1-7/8" pinion starting in the 1969 model year. 1970 RW (Plymouth and Dodge mid-size) were the last models to use the 1-3/4" which appeared in a 2881489 case. This assembly was typically used in high weight/medium horsepower applications through high weight/high horsepower applications. Pinion depth and bearing preload is set with shims. Differential bearing setting (ie. backlash ) is set with threaded adjusters.

1-7/8" tapered stem pinion (aka. '489')
 Carrier casting numbers: 2881488, 2881489 (1969-1974). This assembly was introduced in 1969 and was phased-in to replace the 1-3/4" unit through 1970. Note: the 1-3/4" pinion also appeared in some '489' carriers during this period. By 1973, the '489' was the only unit available in passenger car applications. This assembly was typically used in high weight/medium horsepower applications through high weight/high horsepower applications. Pinion depth is set with shims, preload is set with a crush sleeve. Differential bearing setting (ie. backlash ) is set with threaded adjusters.

[Brillo1974]

Just got this off My Mopar
 By 1973, the '489' was the only unit available in passenger car applications. This assembly was typically used in high weight/medium horsepower applications through high weight/high horsepower applications.

Not too sure about this one, I have a 741 323 sure grip in my 74 that had a 318 in it stock. I would think it would be a lot easier to find a 489 if it were true.

[70chall440]

I cannot verify if the information is correct, only copied from the interweb..

[Brillo1974]

No biggie, how's it going on the car?

[1 Wild R/T]

Not too sure about this one, I have a 741 323 sure grip in my 74 that had a 318 in it stock. I would think it would be a lot easier to find a 489 if it were true.

Only a handful of 741's were installed in 70 model year...  Axle assembly codes 087 a 3.55 SG & 088 a 3.91 SG (both A body) & 100 a 3.23 open (E body).... 489 was the only 8.75 used from 71 up.... If you think that 741 came stock in your 74 check the date code on the ring gear.... Someone swapped it to get a sure grip.... Parts were being swapped on these cars days after they left the dealer, what you think is stock rarely is....   

[twoterpilot]

 

[Brillo1974]

Only a handful of 741's were installed in 70 model year...  Axle assembly codes 087 a 3.55 SG & 088 a 3.91 SG (both A body) & 100 a 3.23 open (E body).... 489 was the only 8.75 used from 71 up.... If you think that 741 came stock in your 74 check the date code on the ring gear.... Someone swapped it to get a sure grip.... Parts were being swapped on these cars days after they left the dealer, what you think is stock rarely is.... 

You are correct about my 741 not being correct, which I assumed hadn't been changed since the car only has 70K on it and everything was stock. It came with 2.71 open gears in it (per my buildsheet) so someone changed the center section with the 323 sure grip.