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1948 - 1956 F1, F100 & Larger F-Series Trucks Discuss the Fat Fendered and Classic Ford Trucks

Swapping 9" Center Section

 
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Old 06-26-2015, 02:43 PM
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Swapping 9" Center Section

Like so many others, I want to get to a taller (numerically lower) gear ratio for the '56. Currently installed is a 9 inch from I think a '62 F100, I'll call this center section "A".

Years ago my dad parted out a 67 Galaxie and saved the center section from it. I'll call this center section "B".

Section "A" has a 4.10 ratio, 28 splines, and the fill hole located in the casting.
Section "B" has a 2.75 ratio, 31 splines, and no fill hole.

The 2.75 ratio would put the Lincoln Y Block right at 2300rpm at 65mph and leave some room to stretch it's legs still. It seems worth a shot to try the tall gears before purchasing a set of 3.00 or 3.25 to gauge a good cruising RPM.

With that in mind; what parts can I swap to make the two center sections play nice? If I disassemble both and try to fit 28 spline side gears into "B" I'll need to add a fill hole to my axle housing if that's an option. Is it possible to swap the "B" ring gear onto "A" carrier and then swap the pinion and retainer to "A" and avoid drilling a new hole in the axle housing? My measurement tools currently are only a set of calipers and feeler gauges, if buying a dial indicator to confirm backlash is good idea I'm not opposed to picking up one.
 
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Old 06-26-2015, 04:03 PM
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Edited: No carrier breaks on Ford 9"s, but carriers are different between 28 and 31 spline models. So the "B" pumpkin isn't going to work with your axles.

Do you have really short tires?
 
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Old 06-26-2015, 04:53 PM
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Originally Posted by ALBUQ F-1 View Post
Edited: No carrier breaks on Ford 9"s, but carriers are different between 28 and 31 spline models. So the "B" pumpkin isn't going to work with your axles.

Do you have really short tires?
Tires are 27" tall, not what I would call really short. Transmission is a T98 so there's no overdrive to lower the RPM's.
 
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Old 06-26-2015, 06:02 PM
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You can probably pick a 9" pumpkin in the ratio you want for cheaper than screwing with what you have. If you have never done a 9" they can be a pain, as Jim (Underthebridgejim) can attest to. Easy work if you have done some. But once you split the carrier to do side gear work or anything you will find you need parts and then it only takes time and money from there. The ratios you are looking at are very common and should be found pretty cheaply.

You don't say what engine you have but I will go out a limb a suggest a 3.25 gear for the 27" tire.
 
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Old 06-26-2015, 08:42 PM
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Engine is a 1953 Lincoln 317. I bumped the timing a bit, changed the distributor to the modern vaccuum advance, running rams horn exhaust manifolds and have a four-barrel 600cfm Edelbrock on top. An older shop manual states the output should be about [email protected] and 305 ft/lb at 2300rpm and it feels like that is pretty spot on. I figure a cruise speed of 2200-2500 @ 65mph would be the best match.
 
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Old 06-27-2015, 09:36 AM
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Well, I grabbed a couple cold ones and some wrenches last night to see what would pan out.

Somehow the 4.10 gears had turned into 3.25, huh? Something isn't jiving there. Based on tire size, engine RPM, and road speed, even turning the tires and counting rotations everything pointed to a 4.10 ratio. Pulling the ring and pinion and counting teeth yielded 39/12 = 3.25 I'm still confused on that one.

Oh well, I had set out to see what would fit and still had a cold one. I ended up using section "A" as a base, swapped the ring gear and pinion with support from "B" to"A" and had to swap the yoke to stay with "A". The yoke from "B" was an inch longer than "A". At the end of the night I had a 2.75 geared 28 spline third member ready to install in the truck, now with a guard on the pinion support.

I've been inside a few other ford axles (7.5, 8.8, 9.75) but the 9 inch is the most basic I've been around. Adjusting the backlash by turning the large nuts on the side instead of carrier shims is great. Now to get it back in the truck...

 
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Old 06-28-2015, 11:50 AM
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Originally Posted by ZSK View Post
Years ago my dad parted out a 67 Galaxie and saved the center section from it. I'll call this center section "B".

Section "B" has a 2.75 ratio, 31 splines, and no fill hole.
31 spline axle shafts: Your '67 Galaxie 9" has a 9 3/8" ring gear.

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

EVERYTHING else is different!
 
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Old 06-28-2015, 01:03 PM
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Originally Posted by NumberDummy View Post
31 spline axle shafts: Your '67 Galaxie 9" has a 9 3/8" ring gear.

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

EVERYTHING else is different!
The picture shown above doesn't appear to be a 9-3/8, doesn't have the curved top rib.
 
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Old 06-28-2015, 07:26 PM
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Originally Posted by ALBUQ F-1 View Post
The picture shown above doesn't appear to be a 9-3/8, doesn't have the curved top rib.
OP said 1967 Galaxie with 31 spline axle shafts, but is it really a 1967?

If a 1966/72 Galaxie/LTD has 31 spline axle shafts, has 9 3/8" ring gear.

But, if it's a 1965 Galaxie/LTD with 31 spline axle shafts, has a 9" ring gear.

Bona fides:
 
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Old 06-28-2015, 07:41 PM
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Swapping in a used R&P can be a lesson in futility, unless extremely lucky in setting up the lash. Even a small change in the previous wear pattern can cause major howl and very short life. (BTDT have the T-shirt...) That's what makes the 9" drop out carrier so popular, just swap the entire carrier rather than just R&P.
 
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Old 06-29-2015, 03:11 PM
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Originally Posted by NumberDummy View Post
OP said 1967 Galaxie with 31 spline axle shafts, but is it really a 1967?

If a 1966/72 Galaxie/LTD has 31 spline axle shafts, has 9 3/8" ring gear.

But, if it's a 1965 Galaxie/LTD with 31 spline axle shafts, has a 9" ring gear.

Bona fides:
It was/is most definitely a 9" ring gear and 31 spline side gears. I was too young in when we parted it out to remember the year, but I do remember getting the crap stung out of me when I bumped the football sized wasps nest under the dash while I was pulling interior trim. It's quite possible that it was a '65 as the section would leave us to believe.

Originally Posted by AXracer View Post
Swapping in a used R&P can be a lesson in futility, unless extremely lucky in setting up the lash. Even a small change in the previous wear pattern can cause major howl and very short life. (BTDT have the T-shirt...) That's what makes the 9" drop out carrier so popular, just swap the entire carrier rather than just R&P.
I went through that with my Ford Ranger that I had. Had a set of 4.10's swapped in and must have gotten lucky. Fingers crossed for this time around also.
 
 
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