gotdust57@yahoo
Well-Known Member
- Joined
- Aug 18, 2006
- Messages
- 346
- Reaction score
- 2
my 73 duster has 8.75 open end with 323 gears but the only ones i see for sale are 742 could someone tell me the difference? thanks
741 0r 742 rear end case?
- Thread starter gotdust57@yahoo
- Start date
-
71DartGuy
Well-Known Member
742 is the casting number for the housing. I think the 742's are the most common ones. The 741's from what I hear are the weakest with the smallest pinion shaft. The 489's are supposed to be the strongest of the three but are a little harder to come by. Which casting is in your car now? Should be on the drivers side of the Pinion housing near the bottom.
I did have a 742 put into a 741 housing.
I think the 741's are actually the more produced. (?)
I think the 741's are actually the more produced. (?)
demon seed
The Original Demon Seed
Here's a couple of articles that explain the differences. http://www.moparts.com/Tech/Archive/axle/21.html http://www.moparts.com/Tech/Archive/axle/1.html
Terry
Terry
Guitar Jones
aka Angry Johnny
The 741 case uses an 1 3/8" pinion stem diameter. It's plenty strong for most street applications but aftermarket gear selection is limited.
The 742 case uses an 1 3/4" pinion stem diameter and is considered to be the strongest of the three due to it's huge rear pinion bearing. Larger than even a Dana 60 bearing. The pinion shaft is also larger than the Dana 60.
Both these rear ends use shims to determine pinion bearing preload.
The 789 case is the latest and it uses an 1 7/8" tapered pinion shaft with a crush collar to maintain pinion bearing preload. If you convert this to a solid spacer and shims available on the aftermarket it is nearly as strong as the 742 but the rear pinion bearing is smaller.
As a side note when MP contracted to make their aluminum 8.75 center section they based it off of the 742 case and it uses the 742 gear set and bearings.
The 742 case uses an 1 3/4" pinion stem diameter and is considered to be the strongest of the three due to it's huge rear pinion bearing. Larger than even a Dana 60 bearing. The pinion shaft is also larger than the Dana 60.
Both these rear ends use shims to determine pinion bearing preload.
The 789 case is the latest and it uses an 1 7/8" tapered pinion shaft with a crush collar to maintain pinion bearing preload. If you convert this to a solid spacer and shims available on the aftermarket it is nearly as strong as the 742 but the rear pinion bearing is smaller.
As a side note when MP contracted to make their aluminum 8.75 center section they based it off of the 742 case and it uses the 742 gear set and bearings.
JohnnyJet
Well-Known Member
Ive been told the "89" case is the best one to have. No Idea why but thats what I have and Im not gonna buy a new one.
340mopar
Sorgermotorsports
The 489 case has a bigger pinion diameter at the gear end than the 742 but both pinions have the same size outer bearing pinion diameter and a shaft or pinion is only as strong as its smallest diameter so both pinions have the same shear strength. But being the 742 has a smaller pinion diameter at the gear end it uses a larger bearing than the 489 so it can carry more load than the smaller bearing on the 489. This is why the 742 is considered stronger than the 489.
Chuck
Chuck
daredevil
Well-Known Member
Am i getting this right? I can run a 742 pinoon and bearing in my 741 case. So the cases are the same just a different bearing and pinion. is the seat for the race the same size? why 2 different no.s if its internal parts?
NO WAY, The complete third members will interchange, the Sure grips will also fit in any of the cases. The ring and pinions are specific to the case.
-
Similar threads
- Locked
