Case differance's

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Demon Scamp

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what are the main differences between the 741 and 742 8 3/4 center sections?

Thanks
Demon Scamp
 
so either one could be a sure grip or could have a after market posi unit installed, the main reason i ask is, I was offered which ever case i wanted for free, i have a friend that has like 7 or 8 741 and 742 cases sitting under his work bench just rusting

Demon Scamp
 
either case can take a sure grip or spool, but they each require there own case specific gear set. There are a few new ratios avalible for the 741, but gear ratio choices are much better for the 742, and it is the stronger of the two.
 
I'd choose the gears you want if they are good. 741 came behind 340's. I have one with about 400,000 miles on it. Second consideration is, get the clutch sure grip if available. If you have to replace gears then get a 742 case.
 
It's not like the 741 is weak, even though it has the smallest pinion shaft, it's just the other 2 options are stronger. If you plan to upgrade in HP, snatch the 742.
 
The 8.8 Ford and 12 bolt GM both have a 1.625" pinion shaft diameter. That's only 1/4 smaller than the 741. That's 1/8" on either side. I don't think we have to argue about how hard the 8.8 and 12 bolts have both been beat the hell out of.
 
hey guys, new question about the cases, last night i scored a 8.75 rear axle out of a 72 duster it has a 489 case bolted in it, the PO said it was all original, so my question is, is the 349 case better then the 741 or 742, dont really matter since i have 1 of each, just trying to figure out which would be better for a 360/727 combo pushing around 425 to 450 HP at the flywheel

Thanks
Demon Scamp
 
Not 389, it's 489 and the 489 Uses a Crush sleeve Which Can be a Pain from what I read.
 

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IIRC - 741 also came behind the Max Wedges..

Also had one behind my 62 hemi'd Dart auto,, no prbs,,

Small/weak(?) yoke diameter is same on all pinions. as shown by above pix.. ^^^^^
 
There's no 349 case. You probably read it wrong. The only cases in 72 were 741 and 489's. The 489 case is plenty strong for your power level. That's what I'm running behind my 408 that's making over 500 lbs ft of torque and about 475 hp. Only problem I ever had was sheared gear teeth. I've seen more teeth sheared off the ring gear than broken pinion shafts
 
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the above pics are of the 8.75 i scored for $250 bucks along with the 741 empty case and the loaded 742 case, was kind of disappointed after i got the axle opened up to find a 2.76 open diff in the 489 carrier, but never the less, i still feel i got a good deal.
Can anyone tell me if this 742 has a cone type or clutch type sure grip in it?

Thanks
Demon Scamp
 
If you were making 800hp it wouldn't matter if you used the 741, 742 or 489.
The problem when it breaks will not be because of the gear or pin strength, it will be the cap that ruins the day. .
 
The 741 is plenty strong but you will find more parts for the 742. I have a 741 in my car and it took several tries to get the correct diameter pinion shims. Wider variety of new gear ratios available as well. I like my 741, found a used set of 3.23s (not available new) and installed them on an Eaton TT dif. It's what came on my car so I am keeping it.
 
8.75 case number and strength is one of the BIGGEST myths in the mopar world. It's the BS that keeps on giving. :)

Good buy on that rear housing for 250 with a clutch SG.
 
If I'm following this thread right. Do you now have a 2:76 sure grip in a 489 case you want to get rid of? I may be interested.
 
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