657 Differential Case gear change

[The Beep]

Hi, hoping for some advice. Other than swapping complete rear-ends I don't have much differential experience. I have a casting number 1820657 (1957-1964) carrier in my 68 4 speed Roadrunner with what I believe is a 4.56 gear. The 2 pictures are of my rear. I understand that the 657 also qualifies as a "741" case so I can use 741 gears. I would like to change to a gear better suited to the highway.

Do I need a special ring and pinion for a suregrip or are they all the same?

This is available locally and I wondered if it was suitable?

Description
3.23 ring and pinion gears for 8.75 Mopar differential. Came out of 741 case. 10 spline. In good condition. $200

 

[wyrmrider]

ever try an Od 4 speed?

 

[The Beep]

ever try an Od 4 speed?

Nope. What in particular tranny do you mean?

 

[The Beep]

Nobody?

 

[YY1]

SG units are interchangeable between carrier castings.

Ring and pinion sets are specific to the different castings.

However, I'm not familiar with the 657 casting.

If you have on good authority that it's the same as a 741, then logic should follow that the same applies to the SG unit.

 

[The Beep]

Well my 657 knowledge is from the internet, lol! I am just surprised that nowhere i have read mentions this. Perhaps because its a non issue i guess. Just hate to waste $200!

 

[Kernel Sanders]

Personally I would just find a known good gear set of your choosing already set up in a case.
If its an open carrier and going to a suregrip carrier, just take a reading of the backlash before removing the open and reset it as close as possible when reinstalling the suregrip.

 

[wyrmrider]

92-4 518 / 92 RH with adapter

 

[The Beep]

92-4 518 / 92 RH with adapter

Isn't the 518 an auto? I wanna stay manual...