8 3/4 rear end LSD identification

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MagnumBarracuda

MagnumBarracuda

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Took the third member out of my 8 3/4. I understand the case is a 741 but i'm not sure what the LSD is. It does not look like sure-grip units i see online. Can anyone identify what brand/type it is? The whole setup is behind a 500 ft-lb 408.

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That is NOT a clutch type, it is the "cone" type, generally less desirable than the earlier "clutch" type unit. Fine for a street car tho
 
Get a 489 case for that kind of power. Your 741 has the smallest bearings, pinion diameter and is the weakest of the three carriers.
 
That’s a aftermarket call cone type. Do what you want but the 741 is the plenty capable carrier. How many 741’s have you seen fail at the pinion bearing? By the way the 741 pinion diameter is 1.375. The much bragged on 9” Ford? 1.313!
 
MagnumBarracuda said:
Its 3.55. There are different types of sure grip?
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Yep, there are two common types of mopar 8 3/4 sure grip, clutch and cone (yours is a cone), and about five other aftermarket types of lsd. Some of those are not available for an 8 3/4, and they arent cheap generally, if they are available.
Also, personal opinion, the 741 case has gotten a very unfair and untrue rep as the weakest casting. If you look on DrDiff's site, he shows the three pinions side by side, and the weakest part of the pinion is identical on all three shafts. The only real drawback of a 741 case is lack of gear ratios and availability. I think race hemis used a 741( in 64 and 65, ) i KNOW the max wedges did.
 
SGBARRACUDA said:
That’s a aftermarket call cone type. Do what you want but the 741 is the plenty capable carrier. How many 741’s have you seen fail at the pinion bearing? By the way the 741 pinion diameter is 1.375. The much bragged on 9” Ford? 1.313!
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But the 9" has the extra support bearing. Wish I could connect the OP with @pettybludart here. He hashed his 741 and replaced it with a Strange S60 in his 408 66 Dart. He has been racing that for a decade. The 741 didn't last a season. A healthy 408 with a 3.55 might not be as hard as Scott was on his because a street car doesn't hook that hard.
 
It's not the pinion that typically fails, its normally deflection in the case and caps, causing the breakage
 
With that kind of torque NO 8 3/4 is going to last long, especially at the drag strip on slicks and a glued track. You need to step up to a 9 1/4 or a dana 60.
 
toolmanmike said:
But the 9" has the extra support bearing. Wish I could connect the OP with @pettybludart here. He hashed his 741 and replaced it with a Strange S60 in his 408 66 Dart. He has been racing that for a decade. The 741 didn't last a season. A healthy 408 with a 3.55 might not be as hard as Scott was on his because a street car doesn't hook that hard.
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Well here we go again. 9” HAS to have the nose bearing. The inner and outer bearings are a mear 1/2” apart! The nose bearing is there to give lateral support to the pinion.
 
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The Mopar Performance LSD’s have the same “round” viewing port and additional springs (like in the OP’s pic) over a factory stock sure grip.
The OP has a cone type Sure Grip
 
Surprised it did not have the same issue I had.

mine was a 742 case changed from 4.56 to 3.55.

Pinion Depth issues for me! 741/742 used Dana/Spicer 4 pinion clutch units in the center. They were slightly smaller in circumference! Had swapped my center to the 489 style SG at some point, Long story! I had to shave the pinion face to keep from hitting the center and get correct gear mesh alignment.

It does not look like a standard 489 type center to me either in the pic. I suspect an aftermarket center.

Doctor Diff can shed some light on these issues!
 
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Yeah the MP Sure Grips use 5 springs.
Check out the OP’s pics, there’s 3 springs together and 2 springs on the other side.
 
you have an aftermarket "sure - grip " unit ,,, NOT a factory sure - grip unit ( cone type ) -- note the lock bolt for the center pin ,,, factory sure - grip units DO NOT have this bolt -- possibly you have an Auburn unit -- 741 case is fine and as stated case will fail before the pinion breaks.
 
SGBARRACUDA said:
That’s a aftermarket call cone type. Do what you want but the 741 is the plenty capable carrier. How many 741’s have you seen fail at the pinion bearing? By the way the 741 pinion diameter is 1.375. The much bragged on 9” Ford? 1.313!
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The Ford 9" gets its reputation for two reasons. One is there is a little bearing dink on the end of the pinion that goes into a roller bearing in the carrier housing. This helps support the pinion gear.
The other point is the offset of the pinion below the axle centerline. This creates greater gear tooth strength.
The disadvantage to this is higher friction and heat generated in a 9".
 
Dale Davies said:
The Ford 9" gets its reputation for two reasons. One is there is a little bearing dink on the end of the pinion that goes into a roller bearing in the carrier housing. This helps support the pinion gear.
The other point is the offset of the pinion below the axle centerline. This creates greater gear tooth strength.
The disadvantage to this is higher friction and heat generated in a 9".
Click to expand...
Re read post 14. That is why it has the nose bearing.
 
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