Educate me on 8 3/4 case #'s ???

[brads70]

Hi all,
I'm new to the 8 3/4 stuff I notice people looking for certain case #'s. What's with that? Does it depend on the gear ratio, if it will fit in a cetain case # ? Do they all bolt into any housing?
Thanks Brad

[Bluemonster71RT]

My car had a 489 case and whne I was going to order a new dropout from MRE I was told that the 742 was a stronger unit. I don't know if that's a fact but it sure does look stronger than my original 489.  But yeah both will bolt up to the housing.

[HemiOrange70]

http://www.planethoustonamx.com/main/chrysler_8_34_rearends.htm

as far as I know the 489 is the strongest case. check out the above link for more info

[moparmaniac59]

If you don't want to have to fool with the crush sleeve then a 742 case is the way to go. Pinion depth is set with shims instead of the crush sleeve. It has a larger rear pinion bearing than the 489 case. If you have a 489 case, you can get a sleeve kit with shims to replace the crush sleeve for ease of installation. If you have to change the yoke out, it makes it a ton easier!!

[brads70]

I don't have anything now. My car came with the 6cyl rear end, that has to go! car now has 440. I have about 3/4 of the parts to build a 9" Ford that I can use. I'd like to keep it all Mopar if I could. Just feels wrong not using Mopar in a Mopar? I'm just so familiar with 9" stuff and know nothing about 8 3/4's?

[Chryco Psycho]

the 3 common carriers are 741 with 1 3/8" pinion
742- 1 3/4" pinion
& 489 -1 7/8" pinion
 the 742 is the strongest due to the crush sleeve in the 489 as mentioned
if you are replacing gears the gear set has to match the carrier # or it wont fit , thereis a conversion brg to installl & 742 gear set into a 489 carrier as well
 All carriers bolt into all 8 3/4" housings & all use the same sure grip units & axle spline

[femtnmax]

If I remember correctly, the first hemi super stock drag cars were running 8 3/4 rear differentials.  And later, the hemi automatic cars used the 8 3/4 diff.  It's a plenty strong unit and you can keep it ALL MOPAR
The units without the crush sleeve are more liable to retain dimensional accuracy in hard use.  That's what I'm using.  JMO.

[macsdaddy]

the 3 common carriers are 741 with 1 3/8" pinion
742- 1 3/4" pinion
& 489 -1 7/8" pinion
 the 742 is the strongest due to the crush sleeve in the 489 as mentioned
if you are replacing gears the gear set has to match the carrier # or it wont fit , thereis a conversion brg to installl & 742 gear set into a 489 carrier as well
 All carriers bolt into all 8 3/4" housings & all use the same sure grip units & axle spline

So with the conversion bearing you can pretty well mix and match everything?

[Chryco Psycho]

nothing from a 741 will fit the 489 but the 742 gears can be installed with shims into the 489 carrier

[tactransman]

there is a conversion brg to install & 742 gear set into a 489 carrier

I did not know that!

[jims challenger]

  LOL!!!!
Here's a picture for reference...
an old 741...(stamped 1820657)
2070742
2881489

[71chally416]

Another reference.
http://www.autohobbydigest.com/8_75.html