ford 9" center section questions - NJFBOA - Home of New Jersey's Camaros and Firebirds

spina74 · 11-02-2011, 12:23 AM

I have a ford 31 spline posi unit, on a stock nodular center section with 3.55 gears. ALL PARTS ARE USED. I dont plan to use this set come next season but I would like to hit the track again before this season is over. Since I wont be running on my radials this time, though if I can get wheels I will. How much of a launch can this center handle without any failure. I'm making 410hp 399tq, but I can't find anything on the internet about how much the posi's or nodular centers can handle.

sweetbmxrider · 11-02-2011, 07:21 AM

What posi? You aren't near the power level to do damage to the 3rd member IMO but I'm not well versed in 9 inch rears.

WildBillyT · 11-02-2011, 08:35 AM

I can't remember the exact numbers but you are below them. The trac lok will be the limiting factor. The center section is very strong. I have heard that the "normal" limit for them in a properly assembled rear with a good pinion support is 600hp, but many run more than that.

spina74 · 11-02-2011, 11:30 AM

So if I slip the clutch at 4000 again I'm probably not going blow anything like I did the 10 bolt?

WildBillyT · 11-02-2011, 11:50 AM

Quote:

Originally Posted by spina74

So if I slip the clutch at 4000 again I'm probably not going blow anything like I did the 10 bolt?

In that case I'd say it would come down to the condition of the parts more than their overall capabilities. How's your driveshaft?

spina74 · 11-02-2011, 12:00 PM

Quote:

Originally Posted by WildBillyT

In that case I'd say it would come down to the condition of the parts more than their overall capabilities. How's your driveshaft?

I went with a chrome moly when I did the rear. I checked the posi it wasn't cracked anywhere, the gears didn't have any signs of wear, and the pinion support didn't have any damage either.

sweetbmxrider · 11-02-2011, 12:09 PM

I flashed my converter to around 32-3400 the other night and got a 1.69 60 on qtp's. Drove home from etown and have been drivin since with no problems. Like Bill said, its not really what the parts are capable of rather what the current condition of said parts will take.

shepss217 · 03-15-2012, 11:07 AM

yeah i think that center section is good to atleast 600 hp, maybe more, the only thing i would change is the posi unit and put a full spool in it, that would probably be the only thing to fail you eventually

NJ346 · 03-15-2012, 06:53 PM

I have to disagree with the above statements. 31 splines is not enough at your power level. I put within ~5hp/tq of you and hurt the 31 spline axles in my moser 9 inch. The car still drives, but I inspected the axles and I definitely hurt one of the axles. If you have the parts already there's nothing you can do about it. I have only 10 passes on this rear with this power level and it hurt it. Best 60' was a 1.69.

WildBillyT · 03-15-2012, 07:00 PM

(Torque of your car) x (Your first gear) x (Your rear end gear ratio) x (90% efficiency).

7000 per axle is a Moser 31 spline axle's limit. They say each axle should be rated for your number.