9 inch prolight diff gears

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steve cowan
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9 inch prolight diff gears

Post by steve cowan » Sat Feb 07, 2015 5:48 pm

hi guys,i am getting a new diff centre done at the moment and the shop is telling me i cannot use pro gears in a street application as it will tear the teeth up in 30 minutes of driving,i have two questions -1/is this true? 2/ will 9 inch street gears handle a 10 inch slick with transbrake application (later this year)the vehicle is a street/strip 3400pound utility driven to the track and weekends,383sbc 532 hp @ 6800rpm with provisions of a 200 shot on top,turbo 400 5000rpm converter,leaf spring rear end caltracs,going to run 10'' drag radial and footbrake,have run this combo previously but wih a 420 hp small block run mid 11 @ 115 mph street gears and 3500rpm converter,the new diff centre is a new twin rib case,truetrac locker,billet pinion support,1350 billet yoke,billet 31 spline diff axles,i want to make this setup as reliable as possible and this car is not a trailer queen and does get driven as i am worried the smaller pinion will give me grief in the future,all feedback appriciated :?: :?: :?: :?: :?:

Blueoval Ralph
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Re: 9 inch prolight diff gears

Post by Blueoval Ralph » Mon Feb 09, 2015 8:19 am

The only 9310 gears that will last in endurance apps is the Gleason gears used by the NASCAR guys But at 2,500.00 a set not sure if that's in your budget.

BirdMan
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Re: 9 inch prolight diff gears

Post by BirdMan » Mon Feb 09, 2015 8:50 am

1/ I don't know as I haven't tried it.

2/We have a 412W w/??? hp ran 9.69 w/3100 lb car 10.5" M/T or Hoosier slicks, ladder bars, adjustable shocks. Diff is M/W 35 spline spool with 4.30 cheap on sale Summit street gears ran 4 years now, haven't had to use the Motive gears yet (no noise from rear at all). Leave at 4,800 on transbrake shifting at 7,000 using a C4. Dead stalls 6,000. No nitrous, all n/a motor. Carrier bearings are the 3.062 early Ford Nodular center section I have one in my car too.

2a/31 spline?? Why not 33 at least! because of my experience with a stick SBF 302/319/347 4spd/5spd over the years starting with 289 HP 28 spline axles. Went to 31 spline stock and then to 31 spline aftermarket for a bunch of years and finally went to 33 spline Moser's because of twisting them, but leaving at 8,000 was not easy on parts until started using the McLeod Soft Lok clutch at app. 700 lbs pressure.

Son had gone directly to 35 spline from stock 28 when he went to 351C w/C4 years ago.
Dale C.

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Re: 9 inch prolight diff gears

Post by BirdMan » Mon Feb 09, 2015 12:27 pm

I also sanded/smoothed all tooth edges so no gouging or sliding off lube??
Dale C.

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Re: 9 inch prolight diff gears

Post by Coloradoracer » Tue Feb 10, 2015 9:28 pm

Pro gears will last more than 30 minutes of driving....However.....They are much softer and not heat treated like street gears and will wear substantially quicker. A quality set of street gears will be plenty as long as you're not doing transbrake launches....I ran a set in my old Nova bracket car for a full season, launching off the brake at 4800 rpm......but it was 1000 lbs or so lighter than what you're describing. Foot braking you'd be fine. You can run the pro gears if you decide to, but you'll need to check backlash on a regular basis and keep an eye on wear... As to the size of the pinion, a standard gear set and the standard pro gears have the same size pinion spline, 28. The larger spline, 31, is much larger and requires a different pinion bearing and spacer with shims.....Not a fan at all of crush sleeves.....
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steve cowan
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Re: 9 inch prolight diff gears

Post by steve cowan » Wed Feb 11, 2015 4:24 am

g,day birdman and coloradoracer,thanks for the replys,birdman- have to go 31 spline billet axles by currie because i am using early ford small bearing axle tubes,i dont want to upgrade at the moment but i am sure i will have to down the track,it sounds like the small pinion gearset can handle more hp than i thought,so i will see how it goes the biggest problem now that we have in australia is our dollar has taken a big dive and the $4500 bill makes me cringe when i see what you guys in the states pay for performance parts and service trust me i am jealous,thanks again steve cowan -''oz'' :D :D :D :D

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Re: 9 inch prolight diff gears

Post by seancarole » Wed Feb 11, 2015 10:00 pm

Moser can do 35 spline axles for small ford ends as well Quick performance rear ends will do the same and save sum $$$$$$!
Good Luck

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