Re: 8 3/4" Third Member Swap Questions?

I know what you mean but this is what I found:

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.

1-3/4" la

On Monday, August 19, 2019 at 8:07:40 PM UTC-7, 62-65-mail...@xxxxxxxxxxx wrote:

Not remembering a 985 8.75. Confusion is contagious. :)

Gary H.

> -------Original Message-------

> Hello,
>
> I have my self totally confused. I had a shop replace my 1965 2.94
> open third member with an unknown year 985 (742?) 3.23 open third
> member. The 985 unit was out of a tapered axle differential. I have
> not been back to the shop yet but before I go I have questions about
> the Thrust Blocks (buttons).
>
> I know I have them on my limited slip 3.23 third member in another
> car, I installed it myself years ago however the more I read the more
> I don't understand open third members. It appears that all Mopar 8
> 3/4 third members have thrust blocks? I pulled the 985 3.23 open
> third member out of the differential and do not recall seeing any
> thrust blocks, did I miss something or did I drop them and lost them?
> However I was not the first person to have been in the differential,
> the person I got it from had pulled the axles to verify the gear
> ration on the ring gear, then put the axles back in the housing.
>
> Tomorrow I am going to pull the wheels and see if I can check the axle
> end play. I know the 1965 differential adjusts with an adjuster ring
> and not shims like the old tapered axle differentials.
>
> The following was copied from the Internet:
>
> Any 8-3/4" center section may be interchanged for another as an entire
> assembly, with the exception of center sections manufactured prior to
> model year 1964 (See Section 1: "Thrust Block Variations").
>
> There was a difference in thrust blocks prior to 1964 that make center
> section
> interchange, as well as axle interchange problematic. The thrust
> block, or "axle shaft
> thrust spacer", it thr block that both left and right axles butt up
> against inside the center
> of the differential. Prior to 1964, all open differentials used a
> thrust block was approximately 1/8" to 1/4" thicker than units made
> after 1964.
>
> Any suggestions other than checking the axle end play would be
> appreciated. Did I make a swap that should not have been done and go
> back to my 2,94 gears?
>
> Thanks
>
> Dennis C.
>