how strong is the 8 3/4 #741 case?

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migsBIG

migsBIG

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So luckily for me, I accidently scored an 8 3/4 rearend, but found out it is a 67 b-body rearend with 11in backing plates and 2:94 surerip to boot. I decided when the time comes, I'll probably swap this rear into my duster. I was thinking that instead of swapping out the diff assembly, I could use it. I'm having a good 300'ish hp 360 being built for the 73' Duster, but no sure home much HP/torque the #741 can handle. an info, experience would be appreciated.
 
A friend ran a 741 case in a 71 Swinger with a mild 440, high stall converter, and 10 inch slicks. After about 7 seasons, a tooth broke off the ring gear, but this was caused by the center section having sat without rotating for several years prior to him buying it from a salvage yard. Over the years of sitting, the oil residue had all drained away from the top.of the ring gear, and it was visibly pitted pretty badly when he purchased it. He simply cleaned it up and sent it. No shame in that spot coming back to bite him after 7 seasons at the track.
 
Since they held up behind Max Wedges, they'll hold up behind your 300 horse 360.
The only issue is gear selection is becoming limited.
 
if you're not launching on massive slicks, doing brake stand burn outs or neutral dropping it like a slap dick teenager it'll last a long, long time. you're more likely to bust a u-joint before anything in the carrier.
 
Running one behind my 317hp 273 in the Barracuda. They really are stout rear ends. Remember anything will break if you are stupid enough.

Back in the 80’s when I drove stupid… we did not care what case was in the 83/4 as long as we had an 8-3/4. The goal was a Dana 60. That was the perfect dream rear. Besides Daisy Duke that is.
 
I ran my '68 'Cuda FB FS at the strip well over 350 times (at one point I had all the timing slips) and turned 13.50's @ 105. All on the original 8 3/4 with 3.55's. With 220,000 miles on it now, all is fine. Just change oil regularly and keep the u-joints lubed and tight.
 
I don't think a 741 differential is measurably weaker than the 742 or 489. Typically when an 8 3/4 breaks it's not because the pinion snaps. Usually the caps will blow out (driver side), the cross shafts will grenade, or the gear teeth will simply shear off.

I'm no expert so don't take my word for it, ask the doctor:

Pinion Comparison - Quality Body Shop Drivetrain
 
junkyardhero said:
if you're not launching on massive slicks, doing brake stand burn outs or neutral dropping it like a slap dick teenager it'll last a long, long time. you're more likely to bust a u-joint before anything in the carrier.
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Dang, now that you brought it up, now I want to do that.
 
If you're putting a B-body rearend in an A-body your going to need to narrow it a bit and probably buy some new axles at that time.

Tom
 
The main problem with a 741 is lack of choice of new gear ratios for one. Only 3.55, 3.73, and 3.91, as far as i know.
A 741 should live a long happy life behind a 360/torqueflite combo. An idiot with a stick can usually kill anything, given enough opportunities. Even with a 350hp 360 and a fourspeed, Id worry more about u-joints than the 741.
 
33IMP said:
....or just get rear wheels with more backspace. (Kinda depends on which year b-body rear.
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and you'll need to be moving the spring perches too.

or at least you should move them...
 
migsBIG said:
So luckily for me, I accidently scored an 8 3/4 rearend, but found out it is a 67 b-body rearend with 11in backing plates and 2:94 surerip to boot. I decided when the time comes, I'll probably swap this rear into my duster. I was thinking that instead of swapping out the diff assembly, I could use it. I'm having a good 300'ish hp 360 being built for the 73' Duster, but no sure home much HP/torque the #741 can handle. an info, experience would be appreciated.
Click to expand...
I have a 4.56:1 pumpkin for the 8 3/4 rear with posi. I'm 76 years old now and want to leave a street drivable car for my daughter who loves my 1970 Duster 340. I'll trade for your 2.94:1 pumpkin with posi if they are compatible. I'm in Diamond Bar, California. barry91765 at g male
 
Last of the Fast said:
I have a 4.56:1 pumpkin for the 8 3/4 rear with posi. I'm 76 years old now and want to leave a street drivable car for my daughter who loves my 1970 Duster 340. I'll trade for your 2.94:1 pumpkin with posi if they are compatible. I'm in Diamond Bar, California. barry91765 at g male
Click to expand...
Nothing wrong with the stock 3:23 gears
 
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