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Author
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Topic: can an 8.8 live with a 33 spline posi unit at 900rw
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1sick65
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Member # 3957
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posted
 
 
I want to build an 8.8 for my car 65 mustang getting a turbo 404ci but cant find solid data on whether or not 33 spline axles and either the auburn or strange posi units will hold up. The car will weigh less than 3200 and be on a 335 DR with a stalled auto and tbrake. Any help is appreciated
Posts: 1457 | From: Sacramento,CA | Registered: Jan 2004
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coupedup
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Member # 9987
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posted
Why not just go with like a built currie 9 inch or a Team Z 9 inch reared or Moser 9 inch housing ?
[ November 04, 2012, 03:30 AM: Message edited by: Nifty50 ]
Posts: 4406 | From: Ca | Registered: May 2010
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1sick65
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Member # 3957
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posted
because people run in the 7's with 8.8s all day. The problem isnt it being an 8.8 or a 9" its finding a posi unit thats up to the task
price is also substantially less
Posts: 1457 | From: Sacramento,CA | Registered: Jan 2004
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JohnB
Tech Moderator
Member # 969
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posted
Braced housing, welded tubes, 33's, and a spool. A true-trac or Detroit locker if you want to drive it on the street.
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1965 Shelby Cobra
1993 Cobra
2012 F150 Raptor
2020 GT500
Posts: 6525 | From: Orlando FL/Redding CA | Registered: Mar 2002
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Boss 327
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Member # 9143
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posted
I have a built 8.8 in my cobra and a currie 9 in my 66 mustang. I would suggest going with the 9.
There's less work you have to do.
[ November 04, 2012, 01:25 PM: Message edited by: Boss 327 ]
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"You'll never truly understand building engines until you can make power N/A. FI overshadows an engines defficiency." Al Papito
Posts: 1789 | From: East Bay | Registered: May 2009
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turbo50
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Member # 6700
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posted
Put a strange s60 in it for that kind of power. That is what is in my 69 camaro
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.........when was the last time YOU built something with YOUR own hands?
I offer quality sidework at reasonable prices. PM ME
Posts: 7606 | From: Discovery Bay, California | Registered: Apr 2006
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1sick65
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Member # 3957
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posted
John- a Detroit or a truetrac are only 31 spline for the 8.8 will they hold the power?
If I go 9" what "posi type" diff will handle that power? I don't want a spool as this is a street car
Posts: 1457 | From: Sacramento,CA | Registered: Jan 2004
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JohnB
Tech Moderator
Member # 969
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posted
quote:
Originally posted by 1sick65:
John- a Detroit or a truetrac are only 31 spline for the 8.8 will they hold the power?
If I go 9" what "posi type" diff will handle that power? I don't want a spool as this is a street car
My bad, meant 31 not 33. Unless you're going to be on slicks, you'll be fine. It really depends on what you want to spend though.
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1965 Shelby Cobra
1993 Cobra
2012 F150 Raptor
2020 GT500
Posts: 6525 | From: Orlando FL/Redding CA | Registered: Mar 2002
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1sick65
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Member # 3957
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posted
This will be a street/ track car, gonna be a 404ls with big single and a pg with stall and brake. I want to keep the 8.8 and run 3.08 gears. Car will be on a 335/18 dr. If I need to step up to an 9" I will but if 31's with a truetrac will do the job then that sounds good
Posts: 1457 | From: Sacramento,CA | Registered: Jan 2004
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1sick65
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Member # 3957
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posted
Are 31's gonna be able to hang?
Posts: 1457 | From: Sacramento,CA | Registered: Jan 2004
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JohnB
Tech Moderator
Member # 969
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posted
Traction is what kills axles, not power level. Dunno about the rest of the folks, but every time I've broken a axle, it was mid-length...not at the splines.
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1965 Shelby Cobra
1993 Cobra
2012 F150 Raptor
2020 GT500
Posts: 6525 | From: Orlando FL/Redding CA | Registered: Mar 2002
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70mach351
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Member # 7528
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posted
fab9 housings come braced, and you can go look at them at chris alstons shop near florin perkins
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70 Mach 1 gettin a make over
2001 Ford F250 Crew Cab 7.3
Posts: 1762 | From: EDH | Registered: Mar 2007
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racsirx
CAFords OG
Member # 1710
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posted
I will be making less than you and going to run 35 spline axles with a spool with my 8.8, you don't like a spool? The only negative about a 9" Rearend is it robs more HP to spin vs. a 8.8 Rearend.
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88 Saleen #564
88 GT 331 NOVI2000
88 Coupe TURBO 9.75@142
95 Cobra R #75-SOLD
06 F250
13 BMW AH3
17 GT350 #5556
GOD'S NOT DEAD
Posts: 20750 | From: Concord & Pittsburg, CA | Registered: Aug 2002
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1sick65
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Member # 3957
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posted
Does a 9" have a posi unit that can handle the power I'm looking to make?
I've got a Fab9 if I want to run it I just didn't want to spend the extra money as it'll be substantially more.
Posts: 1457 | From: Sacramento,CA | Registered: Jan 2004
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1sick65
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Member # 3957
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posted
ok if i decide to go fab9 what diff is up to the task? thinking at least 33 spline-
Posts: 1457 | From: Sacramento,CA | Registered: Jan 2004
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Boss 327
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Member # 9143
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posted
Eaton just came out with a 35 spline truetrac for the 9"
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"You'll never truly understand building engines until you can make power N/A. FI overshadows an engines defficiency." Al Papito
Posts: 1789 | From: East Bay | Registered: May 2009
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1sick65
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Member # 3957
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posted
im thinking about a 33 spline moser wavetrac for the 8.8. should be up to the task. figure $1500 for the whole rear
Posts: 1457 | From: Sacramento,CA | Registered: Jan 2004
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1sick65
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Member # 3957
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posted
it comes with a lifetime warranty too
Posts: 1457 | From: Sacramento,CA | Registered: Jan 2004
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Boss 327
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Member # 9143
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posted
I've heard good things about the wavetrac. Should work out.
[ November 08, 2012, 02:17 PM: Message edited by: Boss 327 ]
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"You'll never truly understand building engines until you can make power N/A. FI overshadows an engines defficiency." Al Papito
Posts: 1789 | From: East Bay | Registered: May 2009
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Boss 327
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Member # 9143
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posted
Here's some info regarding spline count and axle strength:
"When it comes to axles and differentials, there several key specs that you need to know when building or upgrading a rear end. One of the more ambiguous specs is spline count. From the factory, there are several different spline counts, depending on make, model and year of the differential. For custom built rears, you have your choice, but how does one go about choosing their spline count? We talked to JC Cascio of Strange Engineering to find out.
The more splines and axle has, the larger the diameter of the axle; as you increase the spline count, the diameter has to go up in order to fit the additional splines. Each spline is the same size whether the axle has 28 35 splines. A typical Ford 9-inch has 28-spline axles, so this is a baseline in terms of size and strength. The actual OD (outside diameter) of a Ford 9-inch 28-spline axle is 1.205-inch. A 31-spline axle is larger in diameter, measuring 1.330-inch; this equates to an axle that is 35-percent stronger than the 28-spline. Here are the actual numbers provided by Strange Engineering:
28 spline-1.205"- Baseline
31 spline-1.330"- +35%
33 spline-1.413"- +60%
35 spline-1.500"- +77%
40 spline-1.710"- +198%
Anytime you increase spline count, the differential carrier must be changed to match it, so arbitrarily upgrading to a larger count will cost you money that may be better spend elsewhere. We could fill 4 or 5 pages talking about spline counts, but the gist of the matter is this- Bigger is better but isn't always necessary. This is one of those areas where knowledge and experience of a manufacture is invaluable, given the variables involved. "When it comes to spline count, there isn't a magical formula or number that we can publish," Cascio told us, "Axle strength and spline count go hand in hand, but there are other variables at play here, such as tires, transmission, race or street, ect. An example of this would be a 700 hp full-race drag car with slicks and a trans brake will put more stress on the driveline than a street-tired foot brake car with 1000 hp."
[ November 08, 2012, 05:44 PM: Message edited by: Boss 327 ]
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"You'll never truly understand building engines until you can make power N/A. FI overshadows an engines defficiency." Al Papito
Posts: 1789 | From: East Bay | Registered: May 2009
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turbo50
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Member # 6700
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posted
I liked the wave trac unit in my 12 bolt. It only made 2,000,000 hp tho and never seen more than a street tire and a few trips to the moon.
All bs to the side guys doin good things on teamchevelle with wave tracs
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.........when was the last time YOU built something with YOUR own hands?
I offer quality sidework at reasonable prices. PM ME
Posts: 7606 | From: Discovery Bay, California | Registered: Apr 2006
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1sick65
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Member # 3957
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posted
i feel pretty solid about the wavetrac and its warranty- a pricey piece but gotta pay to play
Posts: 1457 | From: Sacramento,CA | Registered: Jan 2004
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