Re: Rear End Strength
[Re: an8sec70cuda]
#2553671
09/23/18 03:50 PM
09/23/18 03:50 PM
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Joined: Oct 2003
Posts: 11,684 W. Kentucky
justinp61
I Live Here
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I Live Here
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Posts: 11,684
W. Kentucky
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Several people have mentioned That a back brace is a waste of time. Not exactly. It will not help ring and pinion life. It's real purpose on both 8 3/4 and 9" rears is to brace the housing so that it won't tow in and bend. Good power and dead hook can/will bend them. By the time you start bending the 8.75 housing, you've already been breaking ring and pinions. For the money it costs to bandaid an 8.75, you could have built a Dana for it and forgotten about it. ^^ This ^^ Not to mention the time pissed away working on it.
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Re: Rear End Strength
[Re: Supercuda]
#2553761
09/23/18 06:35 PM
09/23/18 06:35 PM
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Joined: Nov 2007
Posts: 21,835 Kirkland, Washington
Pacnorthcuda
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Posts: 21,835
Kirkland, Washington
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It has yet to be proven what exactly could be deflecting with a 8.75. I am not convinced the ring is not also a contributor here. I agree, deflection of both undoubtedly contributes to gear tooth failure and the avalanche that follows. I believe that, under severe stress, the carrier bearing preload disappears and allows the ring gear to be deflected enough to lose the contact patch. Does it matter what is deflecting? Once either or both deflect it is all over. It matters in the context of the original post. Ring gear deflection is not dependent on it being a 741,2 or 489.
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Re: Rear End Strength
[Re: 70charger512]
#2553770
09/23/18 06:49 PM
09/23/18 06:49 PM
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Joined: May 2015
Posts: 1,134 Lost in Time
Iowan
super stock
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super stock
Joined: May 2015
Posts: 1,134
Lost in Time
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Does it matter, the diff or spool gets pushed out the back of the case. A billit cap helps but the case fails.
Have a great day Iowan
"obsolete is neat"
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Re: Rear End Strength
[Re: John Brown]
#2553793
09/23/18 07:56 PM
09/23/18 07:56 PM
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Joined: Jan 2004
Posts: 8,301 fredericksburg,va
cudaman1969
master
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master
Joined: Jan 2004
Posts: 8,301
fredericksburg,va
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Since you're going to use a clutch, there is a gizmo out witch is called the door closer. It fits on the clutch rod to slow down engagement just enough to reduce breakage of componites. Wish I had the manufacturs name, but look it up on line. I will use it on my car when done.
Clutchtamer? Yes that's it, thanks. Looks like the Mustang and other small tire class are using this. I'll use it with my 23 spline trans behind the 520 Hemi. Just enough slip to live, street strip.
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Re: Rear End Strength
[Re: lewtot184]
#2553917
09/24/18 12:23 AM
09/24/18 12:23 AM
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Joined: Dec 2003
Posts: 22,696 Bitopia
jcc
If you can't dazzle em with diamonds..
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If you can't dazzle em with diamonds..
Joined: Dec 2003
Posts: 22,696
Bitopia
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I think the real issue is the inner pinion bearing. the 742 has a larger bearing and a 489 is even larger. these are Timken bearings that control the thrust on the pinion. the larger bearing will have more control and less deflection...... 1. I don't think small bearing size differences have any bearing (pun intended) on r&p deflection issues being mentioned here. 2. Not sure what you mean exactly on referring to "larger bearing", since I believe as shaft size increases the actual roller bearings get dispersed in a smaller area, since outer race dia remains the same(?), not sure how that has any impact on r&p deflection issue. 3. This means to me a 489 with a larger pinion dia shaft has less capacity bearings then the 742, but not sure that is an issue anyway with "thrust" overload, leading to likely failures
Reality check, that half the population is smarter then 50% of the people and it's a constantly contested fact.
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Re: Rear End Strength
[Re: 70charger512]
#2554104
09/24/18 03:16 PM
09/24/18 03:16 PM
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Joined: Jan 2003
Posts: 20,192 Park Forest, IL
slantzilla
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Posts: 20,192
Park Forest, IL
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You can debate why until the cows come home, but the fact remains that an 8-3/4 in a heavy high horsepower car is going to break.
"Everybody funny, now you funny too."
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Re: Rear End Strength
[Re: 70charger512]
#2554119
09/24/18 04:11 PM
09/24/18 04:11 PM
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Joined: Apr 2006
Posts: 4,220 West Plains, MO
DrCharles
master
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master
Joined: Apr 2006
Posts: 4,220
West Plains, MO
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What is a "heavy" car exactly? How about "high horsepower"? My nearly-complete Dart 451, 4-speed has a back-braced 8-3/4" with a Dr. Diff 3.91 sure-grip pumpkin, and 295-50R15 street tires. We shall see...
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Re: Rear End Strength
[Re: slantzilla]
#2554157
09/24/18 05:33 PM
09/24/18 05:33 PM
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Joined: Jan 2003
Posts: 25,899 Rio Linda, CA
John_Kunkel
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Rio Linda, CA
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You can debate why until the cows come home, but the fact remains that an 8-3/4 in a heavy high horsepower car is going to break. Not if it never hooks up.
The INTERNET, the MISinformation superhighway
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Re: Rear End Strength
[Re: John_Kunkel]
#2554244
09/24/18 09:39 PM
09/24/18 09:39 PM
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Joined: Dec 2003
Posts: 22,696 Bitopia
jcc
If you can't dazzle em with diamonds..
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If you can't dazzle em with diamonds..
Joined: Dec 2003
Posts: 22,696
Bitopia
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You can debate why until the cows come home, but the fact remains that an 8-3/4 in a heavy high horsepower car is going to break. Not if it never hooks up. There is that.
Reality check, that half the population is smarter then 50% of the people and it's a constantly contested fact.
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Re: Rear End Strength
[Re: DrCharles]
#2554382
09/25/18 10:29 AM
09/25/18 10:29 AM
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Joined: Jan 2003
Posts: 13,376 Marion, South Carolina [><]
an8sec70cuda
I Live Here
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I Live Here
Joined: Jan 2003
Posts: 13,376
Marion, South Carolina [><]
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What is a "heavy" car exactly? How about "high horsepower"? My nearly-complete Dart 451, 4-speed has a back-braced 8-3/4" with a Dr. Diff 3.91 sure-grip pumpkin, and 295-50R15 street tires. We shall see... Your 8.75 will thank you for your tire choice. Like said before, if all you do is spin, you'll likely never break it.
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]
#2554528
09/25/18 03:49 PM
09/25/18 03:49 PM
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Joined: Jan 2003
Posts: 16,376
dogdays
I Live Here
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I Live Here
Joined: Jan 2003
Posts: 16,376
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In response to the "ring gear is deflecting" train of thought, of course it deflects some. but I believe it's more pinion deflection. Basically the major thing the Ford 9" has over the 8 3/4 or 9 1/4 or 12-bolt is the pinion support. That's what seems to me to be making the difference between 8 3/4 and 9".
My friend with the '63 Corvette broke countless 12 bolts before switching to a Dana 60 and hasn't broken anything since.
R.
Last edited by dogdays; 09/25/18 03:51 PM.
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Re: Rear End Strength
[Re: dogdays]
#2554530
09/25/18 03:53 PM
09/25/18 03:53 PM
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Joined: Nov 2007
Posts: 21,835 Kirkland, Washington
Pacnorthcuda
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Too Many Posts
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Posts: 21,835
Kirkland, Washington
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In response to the "ring gear is deflecting" train of thought, of course it deflects some. but I believe it's more pinion deflection. Basically the major thing the Ford 9" has over the 8 3/4 or 9 1/4 or 12-bolt is the pinion support. That's what seems to me to be making the difference between 8 3/4 and 9".
My friend with the '63 Corvette broke countless 12 bolts before switching to a Dana 60 and hasn't broken anything since.
R. I don't know, but..... If ring gear deflection isn't an issue then why do main bearing caps fail?
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Re: Rear End Strength
[Re: CSK]
#2554615
09/25/18 06:05 PM
09/25/18 06:05 PM
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Joined: Dec 2013
Posts: 4,691 Wichita
GY3
master
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master
Joined: Dec 2013
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Wichita
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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 Almost identical experience. I bought a $1300 clutch type sure-grip equipped 742 3rd member for mr 8 3/4 and killed the sure-grip within the first year. Drag radials, sticky track and manual valvebody all conspired to send the rear packing! I did Dr.Diff axles, spool and put ends off an 8 3/4 on a full floater Dana 60 truck rear. It gets abused regularly. Only problem I had was the screw in studs in my Dr.Diff axles were trash and started folding over. Replaced with Strange and all is good! Don't ignore the driveshaft, either! I finally had to order a 1350 Strange unit to hold up along with u-bolt u-joint yoke instead of the strap type. Last year my entire summer was spent fixing driveline issues.
'63 Dodge 330 11.19 @ 121 mph Pump gas, n/a, through the mufflers on street tires with 3.54's. 3,600 lbs. 10.01 @ 133mph with a 250 shot of nitrous an a splash of race gas. 1.36 60 ft. 3,700 lbs.
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Re: Rear End Strength
[Re: Pacnorthcuda]
#2554629
09/25/18 06:18 PM
09/25/18 06:18 PM
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Joined: Jan 2003
Posts: 25,899 Rio Linda, CA
John_Kunkel
Too Many Posts
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Posts: 25,899
Rio Linda, CA
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I don't know, but..... If ring gear deflection isn't an issue then why do main bearing caps fail?
Yep, and the 9" pinion rear support doesn't help when the pinion tries to screw itself out the front of the housing.
The INTERNET, the MISinformation superhighway
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Re: Rear End Strength
[Re: Pacnorthcuda]
#2554650
09/25/18 06:37 PM
09/25/18 06:37 PM
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Joined: Jan 2003
Posts: 13,376 Marion, South Carolina [><]
an8sec70cuda
I Live Here
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I Live Here
Joined: Jan 2003
Posts: 13,376
Marion, South Carolina [><]
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In response to the "ring gear is deflecting" train of thought, of course it deflects some. but I believe it's more pinion deflection. Basically the major thing the Ford 9" has over the 8 3/4 or 9 1/4 or 12-bolt is the pinion support. That's what seems to me to be making the difference between 8 3/4 and 9".
My friend with the '63 Corvette broke countless 12 bolts before switching to a Dana 60 and hasn't broken anything since.
R. I don't know, but..... If ring gear deflection isn't an issue then why do main bearing caps fail? Pinion flexes, teeth break and stack up b/t the pinion and ring gear...carrier gets bound up and pushed backwards, cracks the cap.
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: John_Kunkel]
#2554872
09/26/18 01:38 AM
09/26/18 01:38 AM
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Joined: Jan 2003
Posts: 2,735 541 slobovia
A990
master
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master
Joined: Jan 2003
Posts: 2,735
541 slobovia
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I don't know, but..... If ring gear deflection isn't an issue then why do main bearing caps fail?
Yep, and the 9" pinion rear support doesn't help when the pinion tries to screw itself out the front of the housing.
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Re: Rear End Strength
[Re: 70charger512]
#2579942
11/18/18 07:49 PM
11/18/18 07:49 PM
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Joined: Oct 2004
Posts: 16,479 Canada
CrAzYMoPaRGuY
I Live Here
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I Live Here
Joined: Oct 2004
Posts: 16,479
Canada
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Honest 550hp drag radials and a stick in a heavy car....? I like 8 3.4 rears for street cars. Not that combo though!!! Dana for sure IMO
CrAzYMoPaRGuY
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