8.75 Narrowed, Random thought
#2797402
07/16/20 01:03 PM
07/16/20 01:03 PM
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Joined: Dec 2003
Posts: 22,696 Bitopia
jcc
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If you can't dazzle em with diamonds..
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If you can't dazzle em with diamonds..
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So this has little to do with the other current 8.75" narrow rear end thread, but got me thinking. I'm wondering, does a narrowed 8.75 give the center section a tougher time in high HP applications, in that the narrower the rear, the less "spring/twist" in the axles, and I have never heard this as a strength criteria mentioned when we have the monthly threads on the safe power range for an 8.75"? So we should now include narrowness of the rear in the discussion regarding car weight, tire size/width/compound, gearing, application, back brace, billet caps, etc?
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: 8.75 Narrowed, Random thought
[Re: jcc]
#2797488
07/16/20 03:44 PM
07/16/20 03:44 PM
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Joined: Oct 2007
Posts: 4,209 New York
polyspheric
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master
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New York
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I agree, the torsional distortion is a shock absorber, but how much? Would reducing the diameter mid way allow more rotation? Bill Jenkins remarked on the 12 bolt 50 years ago that he painted a stripe along the axle, and it was safe to use until the stripe went half-way around. !!!!
Boffin Emeritus
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Re: 8.75 Narrowed, Random thought
[Re: cudaman1969]
#2797515
07/16/20 05:02 PM
07/16/20 05:02 PM
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Joined: Aug 2003
Posts: 43,230 Bend,OR USA
Cab_Burge
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I Win
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Bend,OR USA
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I've broken two stock A body 8 3/4 axles, both broke after twisting less than 3 splines I advice a friend who had a set of the early Mark Williams 30 spline axles and spool in his 1971 Demon two rotate the left side twisted axles to the passenger side to untwist it It broke, shattered between the twist in the splines and the bearing end, it was a really ugly break , after about three time trails runs. He called Mark Williams and they told him to NEVER swap axles from side to side on any rear end He ended up buying a set of Yukon race axles instead of buying some of the better American made brands
Last edited by Cab_Burge; 07/16/20 05:03 PM.
Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
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Re: 8.75 Narrowed, Random thought
[Re: jcc]
#2797546
07/16/20 07:21 PM
07/16/20 07:21 PM
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Joined: Jan 2003
Posts: 5,894 Florida
Locomotion
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Florida
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If longer axles actually increases their torsional twist, wouldn't that promote the amount and rate of twist that takes a "set" and eventually leads to breakage?
I'm thinking along the lines of bending a wire back & forth until it eventually breaks. It's easier to bend a long wire so it will heat up faster and break sooner. The shorter wire has the same diameter, but despite the same force being used, it's harder to bend and creates less heat and fatigue. It seems that something will last longer the less it bends/twists.
But I agree with a previous post.....the 8 3/4" has other weak spots, especially the ring & pinion teeth. So anything made stronger in the "chain" of parts will reveal the weakest "link" sooner.
I also read that it's a bad idea to swap axles side to side. Same applies to torsion bars.
Last edited by Locomotion; 07/16/20 07:23 PM.
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Re: 8.75 Narrowed, Random thought
[Re: jcc]
#2797661
07/16/20 10:33 PM
07/16/20 10:33 PM
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Joined: Aug 2003
Posts: 4,688 On the parachute mount
n20mstr
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master
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On the parachute mount
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So this has little to do with the other current 8.75" narrow rear end thread, but got me thinking. I'm wondering, does a narrowed 8.75 give the center section a tougher time in high HP applications, in that the narrower the rear, the less "spring/twist" in the axles, and I have never heard this as a strength criteria mentioned when we have the monthly threads on the safe power range for an 8.75"? So we should now include narrowness of the rear in the discussion regarding car weight, tire size/width/compound, gearing, application, back brace, billet caps, etc? Why narrow a weak rear ? Lol Any thing with decent power will destroy an 83/4 just because of housing flex alone . What’s next ? Pinion angle ? ! Lmao
....BAD A$$ STREET CAR.....
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Re: 8.75 Narrowed, Random thought
[Re: n20mstr]
#2797690
07/17/20 12:16 AM
07/17/20 12:16 AM
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Joined: Jul 2006
Posts: 4,319 Puyallup, WA
StealthWedge67
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When an 8-3/4 center section breaks, I believe a lot of it has to do with the housing flexing which then allows the axles to essentially act as pry bars to distort everything in the case. The shorter the housing is, the less leverage the ends have on the center section, effectively strengthening the overall package. (My theory).
After breaking a relatively stock setup a couple of times, I finally backbraced the housing, installed an MW steel cap, and went with a 35-spline spool and axles. It’s still the stock length, and I’ve been beating on it for a number of years now with no issues.
LemonWedge - Street heavy / Strip ready - 11.07 @ 120
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Re: 8.75 Narrowed, Random thought
[Re: StealthWedge67]
#2797742
07/17/20 09:11 AM
07/17/20 09:11 AM
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Joined: Dec 2003
Posts: 22,696 Bitopia
jcc
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If you can't dazzle em with diamonds..
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Maybe my concern was not clear enough. It does not center (pun) around axle strength or breakage, its more about the hit, or lack of an axle shock absorber effect a shorter axle has, on what many consider already a "weak" 8.75, meaning the possibility a narrower housing has inducing greater shock loads on the CENTER section than a longer axled set-up.
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: 8.75 Narrowed, Random thought
[Re: tabletop390]
#2798238
07/18/20 11:10 AM
07/18/20 11:10 AM
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Joined: Jun 2003
Posts: 52,972 Romeo MI
MR_P_BODY
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Romeo MI
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90% of the rears that I use are 8 3/4 but I also have a 9" in my Rampage.. on the race car it is shortened and I have used ladder bars and a 4 link.. large dia axles on all of them I put a line on them the full length to measure twist.. the biggest issue has always been that the axles will twist at the splines.. I have seen it on axles as new as 1 week old and determined that they take a set right away and tend to stay there.. I back brace right to the end of the housing.. if you look at a stock housing with leafs you will see that the housing bends at the outer edge of the leafs(thus the brace on mine going full length of the housing).. I have only broke 1 8 3/4 of all the years racing and I leave very hard 1.19 60
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