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I have a Ford 9" rear with 28 spine axles . I am just curious how my HP & torque they will hold . It's from a early Mustang so if I change the axles to 31 spline about how much is that going to cost ?
I am building a 429 to about 450 to 500 HP . Will have a 4 speed toploader and 4.88 gears . If I go to a 31 spine will I be able to use everything else the rear comes with besides the axles ?

Jim
 

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i went 9.90s on 28 spline they were moser aftermarket the case cracked after awild. on stock there good to low 12s in a 3400# car. if u go for new 31 your will need to step up side gears in your posi 2 31 spline gears or get a new posi or spool
 

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I have a Ford 9" rear with 28 spine axles . I am just curious how my HP & torque they will hold . It's from a early Mustang so if I change the axles to 31 spline about how much is that going to cost ?
I am building a 429 to about 450 to 500 HP . Will have a 4 speed toploader and 4.88 gears . If I go to a 31 spine will I be able to use everything else the rear comes with besides the axles ?

Jim
the stock case will blow the pinion out . 31 splines will hold up , but will need the aftermarket case or oem N case , plus a pinion support upgrade
 

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300 hp 302 with a 4-speed 3400 lb car -twisted the 28 spline axles, twisted the splines on the stock drive shaft yoke. Once I got that fixed, it spit out the pinion

Granted - I was leaving at 4K basically dropping the clutch on slicks
 

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I put about 150 passes on stock 28 spline axles over a year and a half in a pretty mild 468 mustang (11.30s/1.6 sixtys) with a glide. The final race of last season the driver side snapped at the line. Tires were shot tho which may have caused the car to leave on one wheel.
 

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the stock case will blow the pinion out . 31 splines will hold up , but will need the aftermarket case or oem N case , plus a pinion support upgrade
I remember when Greg and I were only dialing 11.20's we broke the front out of a standard-duty 1 rib case... Axles were 35 spline but anyway it launched the pinion forward SO HARD that it wedged the driveshaft into the transmission!! We had to pull it out with a come-along attatched to the back of the trailer while tapping on the front yoke to help it break loose.
 

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Groceries should be the only thing hauled with 29 spline axles. The price of upgrading to 35 spline is way cheaper than pulling a car off the wall.
 

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You are looking at about a grand ( probably up to 1200 ) to convert to 31 spline, axles and locker, not including the case upgrades that 2slow mentioned. Just tore the end off on mine today, only about 300hp,31inch street tires, locker. Got wheel hop off the line and snapped the end off the driver side axle. Got a friend running in the 10's on 28 splines and slicks with no problems yet, about 3k lbs with an auto. I guess the question is how lucky are you. I'm looking at the parts tonight do this change myself. Just a side note, 28 splines are not sanctioned by any group. Gotta go 31 or bigger to be totally legal.
 

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I put a 472" in a 79 ford pickup with a 175 HP nitrous kit and the very first time I hit it with nitrous on, the 28 spline detroit locker,axles, and carrier were totally destroyed. I converted over to a nodular iron case ,detroit locker, and Moser 31 spline axles and never had a problem thereafter.
 

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I have a Ford 9" rear with 28 spine axles . I am just curious how my HP & torque they will hold . It's from a early Mustang so if I change the axles to 31 spline about how much is that going to cost ?
I am building a 429 to about 450 to 500 HP . Will have a 4 speed toploader and 4.88 gears . If I go to a 31 spine will I be able to use everything else the rear comes with besides the axles ?

Jim
28 spline and a 4speed shouldn't even be in the same sentence,much less anything other than a grocery getter. Listen too 2Slow,he's steering you correctly.;)
 

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Its the 'shock' of a clutch/4 speed (or transbrake automatic) that kills these parts.
I was running 10.00's in a heavy 3700lbs Torino on stock 28 spline axles, stock case, and a cheap "Lock-Right" devise for traction.
But I knew I was on borrowed time.....so before any of it had the chance to break (and cause me to crash), I decided to step up to all aftermarket stuff....Moser case with billet steel caps, Daytona billet pinion support, Steel spool, and Moser 35 spline axles.

Expensive??....yes, but much cheaper than the possible alternative!!
 
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