Anybody know the spline count on the axles in a '66 F100 9"? I want to swap out the steep gears (maybe 4.11) for the 3:1 in a car 9 3/8" which will fit with some housing trimming, I am told.
Eric

 

28 splines unless tampered with. Most I have seen have a 3.25/1 9"

My 64' had a 4 speed and the thing was wound out by 75mph lol. Fun getting there.

 

B7TZ-4234-A (replaced B7C-4234-A) .. 9" Axle Shaft-28 splines = 1957/67 F100.

3.25 commonly used with A/T, 3.50 with 3 M/T w/O/D. Other ratios: 3.00/3.70/3.89/4.11

9 3/8" installed in some 1968/72 F100's, came with 31 spline axle shafts & Traction-Lok.

9 3/8" also installed in some 1966/72 Galaxie/LTD/Thunderbird/Mercury/Lincoln/Mark III/IV, also have 31 splines.

9 vs 9 3/8: Only FIVE parts are the same: Housing gasket, pinion seal, pilot bearing retainer, one pinion bearing and cup.

EVERYTHING else is different! Some of the 9 3/8's parts are different in F100's vs Passenger Cars, rear axle seal for one example.

 

Thanks guys.
Eric