What is the best case to use

[01freeman]

I was wondering what the best case is to use for rear axle. 742, 789...

Thanks

 

[01freeman]

Also what is the best ratio to use. My E body is 340 with 727. I was thinking 3.55 with a Detroit trutrac limited slip. Does anyone have any advice on this.

Thanks

 

[crash520]

Ill be interested in seeing what people say about this as its what Im considering, I have a 489 with 3.55's and am looking at the helical geared Truetrac (clutchless) I want it to paint two black marks down the street solidly, Im reading good things about the new Truetrac but also reading that it needs to be shocked into locking but then wont stay locked.

 

[Chryco Psycho]

The gear angle in the Tru Trac prevents the tires turning at different speed under power but the wheel input will aloow it to rotate in different speeds going around corners .
I answered the carry question on the othere site but As long as you use a spacer & shims to eliminate the crush sleeve in the 489 both are good , the crush sleeve is the weak link .
Gear ratio needs a lot of info , what tire size what intended use , what converter stall speed if Auto etc

 

[01freeman]

So out of the all the 8 3/4 cases the 489 will be durable enough as long as the crush sleeve is removed. How does this case compare to a 741 742 what are the specs of each which one is the heaviest. I think ive found a 489 nodular case. What are your thoughts.

 

[moparleo]

Every thing you want to know about Mopar 8 3/4 diffs and more.
http://www.waywardgarage.com/tech/rearaxlemopar.html