9in or 12bolt
Thread Starter
Staging Lane
Joined: May 2002
Posts: 62
Likes: 0
From: IL
9in or 12bolt Need to put a rear end in my car im leaning towards moiser 9in but a good amount of you guys are running 12 bolts what are the pros & cons of the two and who has the best price thanks <img border="0" alt="[cheers]" title="" src="graemlins/gr_cheers.gif" />
Re: 9in or 12bolt 9 inch has greater strength. 12 bolt has less frictional loss. Both have to do with the distance between the centerline of the pinion gear and the centerline of the axleshaft, which is pinion offset. The greater the pinion offset, the more surface area of the pinion gear is in contact with the face of the ring gear. This increases the strength of the gearset but brings with it an accompanying increase in power robbing friction between the two gear surfaces. The pinion offset in a Ford 9-inch is 2.25 inches compared to 1.5 inches for a GM 12-bolt. 12-bolt is roughtly 2-3% more efficient then 9-inch depending on the ratio of the gears. So it comes down to what you "need" or are willing to sacrifice.
Re: 9in or 12bolt a 12 bolt is more than u will ever be to break...there are millions of cars running 8 seconds and better running 12-bolts...i dare u try and break a properly set up 12 bolt(the ones that are broken have clearences that are waaay off)...the 9 inch is also heavier...i wouldnt put anything ford on my car anyways... <img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" />
FormerVendor
Joined: Dec 2001
Posts: 2,444
Likes: 2
From: WWW.SPEEDINC.COM
Re: 9in or 12bolt I've broke my 12 bolt a few times now.
On a 7k clutch dump on Et streets, the ring and pinion disentegrated.
Just last week, on the way home from the track, the differential broke where the bearing presses onto the side.
On a 7k clutch dump on Et streets, the ring and pinion disentegrated.
Just last week, on the way home from the track, the differential broke where the bearing presses onto the side.
