Ford axle question - difference between 9” and earlier rear ends

[OldNYJim]

I did a little research myself but I figure one of you might be able to give me some reliable info...

I know that the 9” Ford rear end was introduced in 57, and was used through the 80s, but how similar are the early-mid fifties Ford rear ends visually?

I have the AMT Shoebox 50 Ford kit here and the stock axle kinda LOOKS nine-inchy if you squint a little and take into account the soft detail...was the later 9” part VERY different from the earlier models, or was it an evolution of the design?

AMT 50 Ford axle below for reference...thanks in advance!

[Brutalform]

Mostly shock, and spring mounting areas, and different brake hardware. I believe some improvements with certain welds, and improvements to the pinion for some added strength over the years. 

[Ace-Garageguy]

It's been a while, but if memory serves...

While the ('49?) 51-'56 Ford rear ends look "nine-inchy", they're entirely different units. Having a removable pumpkin, they're visually similar enough to pass for most modelers, however.

Nine-inch rear end housings came in a variety of configurations and at many widths for different applications.

Heavy duty and hi-po Fords in '55-'56 (T-bird, wagons and sedan deliveries, police interceptors, and some light trucks) were equipped with the Dana 44.

The factory manual also shows what looks a lot like a Dana 41 for '49-'50 cars, but I don't remember exactly what came in what, and when.

It looks like this, with an integral pinion housing, and a removable round cover on the back.

    

 

 

 

 

Edited January 28, 2020 by Ace-Garageguy

[espo]

The Revell '57 Ford kits have a very accurate looking 9" Differential in their kits. The Differential in the AMT '49-'50 Ford kits have a pretty good representation of what Ford was using at the time. The term "9 inch" for the Ford Differentials has to do with the diameter of the Differential Ring Gear.  On outward appearances the 9" Differential has several distinctive reinforcing webs on the side of the Carrier. The Carrier is a drop out design in which the axles are pulled slightly out of the Differential Housing allowing the Carrier to be unbolted and the Differential Carrier containing Gears and bearings can be removed. This maybe "TMI" but maybe it will help.  

[afx]

Here is the axle in the Moebius 427 Mercury Comet - is this not a Ford 9"?

[Dave Van]

A pretty nice Ford nine inch rear can be found in the 90's era AMT NASCAR stock cars.....any of them.

[Ace-Garageguy]

18 minutes ago, afx said:

Here is the axle in the Moebius 427 Mercury Comet - is this not a Ford 9"?

It looks like one. As mentioned above, the 9" was introduced in 1957, and was a new design, but derived from ideas developed earlier.

From either '49 or '51, Ford used a design that looked very much like it, but was in fact entirely different (and called a "banjo housing" rear end in the parts book).

Even with the real car guys, there's a lot of confusion and misinformation surrounding the earlier axles that look like 9 inchers, but aren't.

This is the pre-9 inch pumpkin. Looks a lot like a 9 inch, eh?

Edited January 28, 2020 by Ace-Garageguy

[Dave G.]

Course depends which 9" you want to represent but generally speaking the 49 and 50 rear ends are close enough in modelling them. I'm building an AMT 49 now and using the stock rear axle for a street and strip type car. The most notably different 9" is one where the carrier is a nodular iron unit used with 427 Mustangs and such. Besides the nearly indestructible material it also had double webs in the front of the housing with a visible N at the top. Several differences internally that wouldn't matter in a styrene model of course.

[OldNYJim]

Really helpful guys - thanks so much for all the info!

As Ace says, there’s a lot of confusion apparently even with the 1:1 guys - I read so many variations of the exact ‘facts’, the more I read the less I knew ?

[Mark]

The shape of the '49 axle differs from the 9" a bit, in the areas where the axle tubes transition to the center section.  A little work with a round file in those areas will go a long way.

The 9" housings do have some changes over the years, the earlier ones are generally "smoother".  The '57 station wagon axle was the one you'd always see referenced in magazine articles as the best looking, the one the street rodders would hunt down.  Not sure if Revell's wagon piece is any different from the one in the sedan kit.  The AMT '57 hardtop piece lacks detail on the gear carrier side.

[Force]

Another reason why many want to use the 57-59 Station Wagon/Rancero 9 inch axle is that it's the narrowest of them all with 57.25 inches.
But I don't understand why hot rodders want the heavy 9 inch axle, the 8 inch axle is lighter and the aftermarket 8 inch axles is strong enough for a light hot rod.

[espo]

38 minutes ago, Force said:

Another reason why many want to use the 57-59 Station Wagon/Rancero 9 inch axle is that it's the narrowest of them all with 57.25 inches.
But I don't understand why hot rodders want the heavy 9 inch axle, the 8 inch axle is lighter and the aftermarket 8 inch axles is strong enough for a light hot rod.

Take a 2800 lb. to a 3000 lb. vehicle with a good 400+ foot pounds of torque. Bring the Tach. up to 3000+ rpm and "pop" the Clutch and watch what happens when the rear tires start to get traction. You'll be out there with the grounds crew helping to clean up the mess. If you're lucky one of the U-joints will go first and then you just listen to the drive shaft beat the tar out of the floor boards. And you're going to want to roll down the window because all of the dust from under the seats will be flying around inside the car.  Been there, done that.    

Edited January 29, 2020 by espo

[Force]

On a light 30's hot rod with street tires you woun't get much grip, so it's not that big of a problem...on a race car with racing slicks and a prepaired track it's another thing.
But the 9 inch axle is heavier than the 8 inch and you want the unsprung weight to be as low as possible, and the aftermarket stuff available for the 8 inch nowadays is stronger than the stock parts and will hold up at least as good as a 28 spline 9 inch axle if not better.
It was another thing years ago when there wasn't much for the 8 inch axle available on the market and you had to do with stock parts and an axle taken out of a junk car, today you can buy everything new and get the axle as you want.

[Ace-Garageguy]

1 hour ago, Force said:

On a light 30's hot rod with street tires you woun't get much grip, so it's not that big of a problem...on a race car with racing slicks and a prepaired track it's another thing.
But the 9 inch axle is heavier than the 8 inch and you want the unsprung weight to be as low as possible, and the aftermarket stuff available for the 8 inch nowadays is stronger than the stock parts and will hold up at least as good as a 28 spline 9 inch axle if not better.
It was another thing years ago when there wasn't much for the 8 inch axle available on the market and you had to do with stock parts and an axle taken out of a junk car, today you can buy everything new and get the axle as you want.

Exactly...but the concept of "unsprung weight" is largely unknown to hot-rodders, and there's a lot of "everybody runs a 9-inch so...baaa baaa...I will too" in play.

Still, if you have your heart set on building a semi-bulletproof car out of junk, it's hard to beat a boneyard 9-inch.

Edited January 29, 2020 by Ace-Garageguy

[Dave G.]

On 1/29/2020 at 11:28 AM, Force said:

On a light 30's hot rod with street tires you woun't get much grip, so it's not that big of a problem...on a race car with racing slicks and a prepaired track it's another thing.
But the 9 inch axle is heavier than the 8 inch and you want the unsprung weight to be as low as possible, and the aftermarket stuff available for the 8 inch nowadays is stronger than the stock parts and will hold up at least as good as a 28 spline 9 inch axle if not better.
It was another thing years ago when there wasn't much for the 8 inch axle available on the market and you had to do with stock parts and an axle taken out of a junk car, today you can buy everything new and get the axle as you want.

Ya the 28 spline axles were the weak link in the 9", at least with slicks. I raced a 67 big block Mustang with slicks and it didn't take long to first twist the splines slightly, then snap the axle. I upgraded the the posi section from detroit locker with 28 splines to the posi with 31 splines and that ended that particular problem.

Edited January 30, 2020 by Dave G.

[mk11]

The moebius 9 inch carriers(front part) are the last ones you would want to pick if you want an accurate model. The axle housing itself is fairly decent. The best ones currently are in the revell bronco, 29/30 model As(newest issue) and the amt 39 wagonrod. More detail here...

http://www.modelcarsmag.com/forums/topic/108330-ford-9-inch-axles-in-scale/?tab=comments#comment-1537844

[Force]

23 hours ago, Dave G. said:

Ya the 28 spline axles were the weak link in the 9", at least with slicks. I raced a 67 big block Mustang with slicks and it didn't take long to first twist the splines slightly, then snap the axle. I upgraded the the posi section from detroit locker with 29 splines to the posi with 31 splines and that ended that particular problem.

Of course the 31 spline axle is stronger but for street use the 28 spline is strong enough, and I'll bet the aftermarket axles available now are stronger than the old stock parts.
The parts availabillity for the 9 inch axle was far better than for the 8 inch and that may be why so many used it even tho' they didn't need the strength.

[Rodent]

Been seeing more guys grabbing 8.8" disc brake rears from mid-90s Explorers. I forget what the exact mods are, but as-built, one axle and tube is longer than the other side. Shorten the longer tube to the length of the shorter one, get another shorter axle shaft, and you have a fairly robust disc brake limited slip axle that is the right width for a 65-66 Mustang or early Falcon. Unless you are running a lot of HP, you aren't going to break an 8.8 in that application, and they are a lot easier to find than a 9".

[alan barton]

Jim, the most visually noticeable thing about any nine inch is that the rear of the housing is noticeably oval in shape, rather than circular, and the surfaces that run around this oval are particularly flat compared to the curved surfaces on may other rear ends.  The AMT 57 Ford rear end, although a nine inch, does not show this detail particularly well.

Another good 9 inch centre section is the one in the late model Revellogam  funnycars. The housing is too narrow for most street applications but does have a brace across the rear. Without checking I think the Revellogram Pro stocks would also have a good centre.

And Ace and Hakan, I am definitely one of those hot rod guys with a nine inch because everyone else has one!  But it looks awesome under the rear of my Model A roadster and forty years ago it cost me $50 so I'm good with that.  I did manage to spectacularly break an axle once with a resultant loss off wheel.  I was taking my engine builder for a run to show him what a good job he had done.  This was a very mild 307 Chevy from an Australian Holden Premier, nothing like 400 hp, probably just over 200, but it hauled A and was good for a 14 second flat quarter in street trim. I was about to shift into second when she turned into a tricycle!

As far as unsprung weight goes, I know you are right but when you have the centre of gravity of an apartment block, it doesn't stress me too much.  This car is a daily driver for me  and has done over 300,000 miles in 35 years so I love the bulletproof reliability.  Oh yeah, the centre is from a 59 Fairlane (your Galaxie)  with 2.9 ration and it was last assembled by the Ford guys in Geelong.  You can't argue with 60+ years out of a gear set!

Cheers

Alan

Edited January 31, 2020 by alan barton
Can't count! 60 years, not 70!

[Dave G.]

2 hours ago, Force said:

Of course the 31 spline axle is stronger but for street use the 28 spline is strong enough, and I'll bet the aftermarket axles available now are stronger than the old stock parts.
The parts availabillity for the 9 inch axle was far better than for the 8 inch and that may be why so many used it even tho' they didn't need the strength.

Oh very true Force, won't deny that.

[Force]

I used to have a 64 Fairlane with a 8 inch and now I have a 63½ Galaxie with a 9 inch and I feel the difference in weight of the axles in the car when you drive over bumps like a train track or something like that.
Finding rear axles nowadays is not a problem as the most popular ones are plentiful on the aftermarket, so you don't need to rob one from a junk car anymore, and of course if you are doing a car for performance you want a strong axle so at least that will hold up even if everything else is blown to smithereens. 

Edited January 31, 2020 by Force