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Ford 12 Tooth Pinion
Posted: Fri Jan 03, 2025 12:18 pm
by got10carz
I have this 12 tooth made by Ford that doesn't roll nice on either a 39, or 40 tooth ring gear. You can see it's smaller than a 11 tooth, weird. Then I thought maybe it's made for a 44 tooth ring gear, but the ratio is 3.66, so why do that. You can see it's cut like a 9 tooth.
Any insight would be appreciated.
Could it be NRS?
Re: Ford 12 Tooth Pinion
Posted: Fri Jan 03, 2025 12:25 pm
by speedytinc
It was the first iteration of a 4:1 set for the "new" heavier 15 sedan. Very short lived until the 10 T pinion was developed to work with the normal 40T ring gear. Thusly not requiring a full axle tear-down to change the ratio.
The ring gear is special cut to match the pinion @ 48 teeth.
Neither can be used with the normal 3.66 gears
I also picked up 2 nos 12T script pinion gears. The vendor was honest enough to warn me they cant be used with "normal" ring gears.
!5 + years later I found a used 48T script ring gear. I have not seen another since.
Re: Ford 12 Tooth Pinion
Posted: Fri Jan 03, 2025 2:41 pm
by Dan McEachern
Thanks John- that is something I have never heard of!
Re: Ford 12 Tooth Pinion
Posted: Fri Jan 03, 2025 3:33 pm
by speedytinc
You are welcome.
Its another of those interesting, short lived design/engineering changes that got dropped to save money & labor costs.
Re: Ford 12 Tooth Pinion
Posted: Tue Jan 07, 2025 6:00 am
by EliasRay
speedytinc wrote: ↑Fri Jan 03, 2025 12:25 pm
It was the first iteration of a 4:1 set for the "new" heavier 15 sedan. Very short lived until the 10 T pinion was developed to work with the normal 40T ring gear. Thusly not requiring a full axle tear-down to change the ratio.
The ring gear is special cut to match the pinion @ 48 teeth.
Neither can be used with the normal 3.66 gears
I also picked up 2 nos 12T script pinion gears. The vendor was honest enough to warn me they cant be used with "normal" ring gears.
!5 + years later I found a used 48T script ring gear. I have not seen another since.
Thank you so much for sharing the info.