Re: Rear End Strength
[Re: 70charger512]
#2552780
09/21/18 12:03 PM
09/21/18 12:03 PM
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Joined: Sep 2003
Posts: 19,388 north of coder
moparx
"Butt Crack Bob"
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"Butt Crack Bob"
Joined: Sep 2003
Posts: 19,388
north of coder
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i have beat on several 741's, [3.91 & 4.10] that i got from /6 trucks and vans that had sure grips, without problem number one. all the pinions neck down to the same diameter at the flange, so not being a rear gear expert by any means, i really don't give it much thought. also, i have only been at 425/435hp, so for an extra 100hp or so, maybe use a brace on the housing ? i never have done that, but if i would, i'd go clear to the backing plates, using inserted tubes for the u-bolts. subframe connectors help at any level, tightening up the car a lot. don't know if this helps or not. i'm sure you will have other responses different than mine. luck to you !
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Re: Rear End Strength
[Re: 70charger512]
#2552787
09/21/18 12:10 PM
09/21/18 12:10 PM
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Joined: Sep 2007
Posts: 14,889 up yours
Supercuda
About to go away
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About to go away
Joined: Sep 2007
Posts: 14,889
up yours
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Where the 8 3/4 fails is pinion gear deflection inside the housing. So diameter at the flange is irrelevant, it doesn't deflect there.
If you really have 550hp and excellent traction you might have a problem and no back brace will handle the pinion deflection. All a back brace does is add extra unsprung weight here, which is exactly what you do not want in a handler. Now if you want to clean up the housing and make sure the tubes are fully welded and straight then that's fine.
They say there are no such thing as a stupid question. They say there is always the exception that proves the rule. Don't be the exception.
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Re: Rear End Strength
[Re: 70charger512]
#2552816
09/21/18 12:49 PM
09/21/18 12:49 PM
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Joined: Jul 2011
Posts: 956 Chicago
PurpleBeeper
super stock
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super stock
Joined: Jul 2011
Posts: 956
Chicago
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In my humble opinion, I think your rear end will be just fine as long as you are running street tires & NOT slicks of any type. (if you run slicks, you need hardened axles & a driveshaft safety loop + ?) If you use slicks, then an 8-3/4" can get maxed out in heavy cars....but I think 550hp would be just fine (no DANA needed).
If you plan to race (at all), then get a copy of the current NHRA rule book. See what safety upgrade requirements your car has & put them in.
In general, I personally love frame connectors & driveshaft safety loops are cheap & pretty easy to install, so I install those whether required by NHRA or not. For street-tire cars, you might want to consider an adjustable pinion snubber OR some old-school "slapper" traction bars....maybe an clamp or two on the front of the leaf springs. Then, just go race & see what your Charger does.
70 Roadrunner convt. street car
440+6, NOS, 4-spd, SS springs
'96 Mustang GT convt. street car
'04 4.6 SOHC, NOS, auto, lowered
"Officer, that button is for short on-ramps"
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Re: Rear End Strength
[Re: 70charger512]
#2552845
09/21/18 01:50 PM
09/21/18 01:50 PM
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Joined: Nov 2007
Posts: 21,822 Kirkland, Washington
Pacnorthcuda
Too Many Posts
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Too Many Posts
Joined: Nov 2007
Posts: 21,822
Kirkland, Washington
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Nick,
Run the 741. It uses a smaller bearing at the pinion head, but not by much, and it's not likely to fail. It also has the significant advantage over the 489 of not using the crush sleeve (they suck).
As always, set up is important, you want a healthy differential section (preferably good aftermarket or a power lock clutch type) and a ring and pinion that is not showing abnormal wear. As far as strengthening, the first area to look at would be the main caps (carrier) but you are very likely fine with stock.
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Re: Rear End Strength
[Re: justinp61]
#2552883
09/21/18 02:55 PM
09/21/18 02:55 PM
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Joined: Sep 2007
Posts: 14,889 up yours
Supercuda
About to go away
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About to go away
Joined: Sep 2007
Posts: 14,889
up yours
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I too would run the 741, never seen one break the pinion shaft, have seen teeth broke, but that's all 8 3/4's. That's the pinion deflecting. the 9" has a support bearing on the end of the pinion that prevents this.
They say there are no such thing as a stupid question. They say there is always the exception that proves the rule. Don't be the exception.
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Re: Rear End Strength
[Re: Supercuda]
#2552890
09/21/18 03:13 PM
09/21/18 03:13 PM
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Joined: Oct 2003
Posts: 11,684 W. Kentucky
justinp61
I Live Here
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I Live Here
Joined: Oct 2003
Posts: 11,684
W. Kentucky
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I too would run the 741, never seen one break the pinion shaft, have seen teeth broke, but that's all 8 3/4's. That's the pinion deflecting. the 9" has a support bearing on the end of the pinion that prevents this. Yes all 8 3/4's suffer from it, the case is big part of the problem. The 9" is a great desigm, just not super strong in stock configuration. I broke two in four wheel drives, one busted the internal housing around the tiny support bearing.
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Re: Rear End Strength
[Re: 70charger512]
#2552897
09/21/18 03:29 PM
09/21/18 03:29 PM
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Joined: Sep 2007
Posts: 14,889 up yours
Supercuda
About to go away
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About to go away
Joined: Sep 2007
Posts: 14,889
up yours
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They all have their issues that's for sure.
They say there are no such thing as a stupid question. They say there is always the exception that proves the rule. Don't be the exception.
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Re: Rear End Strength
[Re: 70charger512]
#2552950
09/21/18 05:10 PM
09/21/18 05:10 PM
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Joined: Jan 2003
Posts: 25,785 Rio Linda, CA
John_Kunkel
Too Many Posts
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Too Many Posts
Joined: Jan 2003
Posts: 25,785
Rio Linda, CA
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As stated many times, all of the 10-spline pinions neck down to the same size at the spline so failures are normally somewhere else but there are exceptions.
The INTERNET, the MISinformation superhighway
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Re: Rear End Strength
[Re: 70charger512]
#2552998
09/21/18 07:01 PM
09/21/18 07:01 PM
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Joined: Jan 2003
Posts: 13,362 Marion, South Carolina [><]
an8sec70cuda
I Live Here
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I Live Here
Joined: Jan 2003
Posts: 13,362
Marion, South Carolina [><]
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Like said before, a backbrace on an 8.75 is a waste of time. If the car is a 4 speed, you'll be a lot more likely to break it. If you never get traction, it'll live a long time.
CHIP '70 hemicuda, 575" Hemi, 727, Dana 60 '69 road runner, 440-6, 18 spline 4 speed, Dana 60 '71 Demon, 340, low gear 904, 8.75 '73 Chrysler New Yorker, 440, 727, 8.75 '90 Chevy 454SS Silverado, 476" BBC, TH400, 14 bolt '06 GMC 2500HD LBZ Duramax
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Re: Rear End Strength
[Re: an8sec70cuda]
#2553010
09/21/18 07:45 PM
09/21/18 07:45 PM
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Joined: Sep 2018
Posts: 257 NC
70charger512
OP
#1 Thread Starter
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OP
#1 Thread Starter
Joined: Sep 2018
Posts: 257
NC
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Like said before, a backbrace on an 8.75 is a waste of time. If the car is a 4 speed, you'll be a lot more likely to break it. If you never get traction, it'll live a long time. I plan on it being a 5 speed (the TKO600) so would ur comment still stand with that?
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Re: Rear End Strength
[Re: 70charger512]
#2553025
09/21/18 08:18 PM
09/21/18 08:18 PM
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Joined: Feb 2006
Posts: 605 TN
1DGEMAN
mopar
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mopar
Joined: Feb 2006
Posts: 605
TN
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The whole key to this is if the car hooks it will kill the 8 3/4. If you only run it with street tires it will spin or your launch will be so soft it won't be a problem. If you put slicks on it,save your money and get a Dana. I have killed 8 3/4 rears with considerably less than 550 hp in A body NHRA stockers.
Real Men shift for themselves
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Re: Rear End Strength
[Re: 70charger512]
#2553056
09/21/18 09:42 PM
09/21/18 09:42 PM
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Joined: Nov 2006
Posts: 1,457 oklahoma
forphorty
pro stock
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pro stock
Joined: Nov 2006
Posts: 1,457
oklahoma
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Like said before, a backbrace on an 8.75 is a waste of time. If the car is a 4 speed, you'll be a lot more likely to break it. If you never get traction, it'll live a long time. I plan on it being a 5 speed (the TKO600) so would ur comment still stand with that? All 4 speed 440s and hemis came from the factory with Dana 60s. I wouldn't expect an 8.75 to last very long in a 500+ hp stick b body.
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Re: Rear End Strength
[Re: forphorty]
#2553066
09/21/18 10:00 PM
09/21/18 10:00 PM
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Joined: Sep 2007
Posts: 14,889 up yours
Supercuda
About to go away
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About to go away
Joined: Sep 2007
Posts: 14,889
up yours
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All 4 speed 440s and hemis came from the factory with Dana 60s. I wouldn't expect an 8.75 to last very long in a 500+ hp stick b body. All? Hmm wonder what they put in Hemi cars before they started using the Dana? Wonder why they started using the Dana? Not all 4 speed Gen II Hemi cars used a Dana. But the point is, the 8 3/4 was failing in that application nd Chrysler went with the Dana.
They say there are no such thing as a stupid question. They say there is always the exception that proves the rule. Don't be the exception.
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Re: Rear End Strength
[Re: 70charger512]
#2553153
09/22/18 02:06 AM
09/22/18 02:06 AM
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Joined: Jan 2003
Posts: 9,826 las vegas
70AARcuda
master
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master
Joined: Jan 2003
Posts: 9,826
las vegas
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Have bought 3 Dana 60 from Doc Diff...Strange Dana 60 make with adjusters makes swapping gears alot easier.
Tony
70 AARCuda Vitamin C 71 Dart Swinger 360 10.318 @ 128.22(10-04-14 Bakersfield) 71 Demon 360 10.666 @122.41 (01-29-17 @ Las Vegas) 71 Duster 408 (10.29 @ 127.86 3/16/19 Las Vegas)
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Re: Rear End Strength
[Re: 70charger512]
#2553158
09/22/18 02:25 AM
09/22/18 02:25 AM
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Joined: Aug 2011
Posts: 2,857 Pattison Texas
CSK
master
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master
Joined: Aug 2011
Posts: 2,857
Pattison Texas
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I wasted $1200.00 on my 8.3/4 in my Charger, put Drag radials on it & killed the 8 3/4. NEVER will i spend money on 8 3/4 again. got a S60 from DR Diff with the S Trac carrier, it cost more but works AWESOME, I dont know my HP but car is heavy 4050 with me, so far 11.33 @ 121.1 1750 DA
1968 Charger COLD A/C Hilborn EFI 512ci 9.7 compression, Stealth heads, 4.10 gear A518 ODtrans 4100lb,10.93 full street car trim 2020 T/A 392 Stock 11.79 @ 114.5
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