Technical 8in vs 9in vs 8.8

I've always heard the ford 9in as the end all for everything got rods and horsepower related, but how does the 8in compair? I have heard people taking 8in transmissions to mid/low 12 second quarters, and others say they'll break if you give it more than 300hp on the street. How much is it built up and how much can a stock 3rd member take? I've also heard good thing about 8.8 in rear ends with the 31 spline axles and the c clip eliminator kit, but its wide and sometimes will not fit without cutting and resplining everything.

I have a 8in in my Falcon and I don't know if it'll handle the 347 I eventually want to build. I've heard that some 3rd members have extra webbing and thus it can handle more. What are the main weak point in the 8in and can they be fixed?

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The 8" isn't a bad rear, and it's not so much its strength limitations as its long-term durability from a OEM standpoint. Ford limited it to 302" non-hipo motors or smaller, and only in the intermediate or smaller cars. You never saw one in a full-size or truck, no matter which motor they had. If you keep torque loads down, it's fine. A 347 with an automatic behind it should be safe, but a manual trans used with enthusiasm will probably break it. I ran a well-warmed 302/4-speed in front of one for years and never broke it, but a 302 doesn't produce the torque a 347 will. Any power-adders, you'll need to step up to a 9".

You can beef up a 8", but you'll save little money over a 9" and still haven't addressed its main issue which is the pinion bearings. This is a design flaw; the bearings are simply too small for extended exposure to moderate loads or short exposure to heavy loads, and the case design prevents fitting bigger bearings. This is the reason Ford limited its OEM use the way they did. I've personally seen more go bad from pinion bearings than actual breakage. But this probably won't be a big issue in a low mileage hobby car if the rear has been rebuilt at some point.

FWIW, a stock 28 spline 9" will be bulletproof in a Falcon as long as no slicks/racing are involved. If you get a small-bearing 9" housing the same width as your 8" in your Falcon, you can re-use your axles and brakes.

Neither 8" or 9" stuff is cheap anymore, so don't discount the 8.8". Nearly as strong as a 'good' 9", they're still pretty inexpensive and can be found in widths that fit your Falcon. I'd go that route before spending big money on a 8" or 9"...

 

8.8".... Enough said.

 

A good 8.8" has 31 spline axles and not 28 spline.

 

I live 80 miles from Quick performance and had them narrow, install 9" billit ends and weld the center to the tubes on an Explorer8.8. That and a set of 31 spline axles cost me $600 six years ago for my 64 Fairlane.

Don't spend money on the 8", the pinion and spider gears are what I've broken in the past with an automatic 351 Fairlane.

 

I think Crazy Steve summed it up pretty well. The 8" pinion bearings will not take heavy pounding. I have never seen an 8" with the extra rib. A 9" WAR casting did have the extra rib. The "holy grail" 9" had a big N cast into it. This is a high nodular iron composition. They are harder to find, but still around. A 9" with the width to fit your Falcon is also harder to find. Some candidates are 57-59 Fords, 67-68 big block Mustangs/Comets. Aftermarket folks such as Currie Enterprises offer custom units at a price. 8.8 rears are a good alternative, and can be found in the right width and axle ratio with a little searching. Some of the Explorers have disc brakes.

 

Comparison of pre 1967 (Single) and post (Twin) rib case

 

Look at it like this.........Everything you do to the eight inch will be as expensive as everything you would do to a nine inch. You will probably find some things for an 8" actually cost more because of less availability.
With a 9" people always want to find one thats narrow. When/if you find a narrow one, people want more money for it. Then it usually has 28 spline "small diameter" axles comparible to an 8".
Best thing to do is find a wide 9" and get the axles machined or buy some new Moser axles and narrow the housing. No matter which way you go, doing it right will get expensive......but it will hold up.

For a decent option at a lower cost I would look at some of the 8.8s and see if I could find one that was the correct width and had factory posi in it. Thats the cheapest way to get a decent rear thats pretty strong ......if you can find one.
Here is some helpful info: Go to Amazon and get this book. Lot of info on where to find what you want as well as rebuilding.

 

You tube 8.8 narrowing. Pretty simple. Thanks for showing mine in our 56 Ford. One side narrow 2same axles. The 8.8 is more efficient do to a raise of the pinion over a 9”. Not a big deal to most.
9” are obsolete by Ford standards even though aftermarket has covered all of it for years..

 

If I remember right, some later explorers came with disks, limited slip, and 31 spline axles, but where offset to one side. I would definitely have to get it shortened as well. As for the 9in getting a housing in cali is nothing if not expensive, not even looking at the 3rd members. I believe currie wanted around 1500 for the housing alone. The shop I was talking to about getting an 8.8 shortened was saying he'd end up getting new axles and housing ends as he doesn't like to reuse old stock stuff and he only wanted around 1000 for everything shortened with the new parts. I'm wondering if he'd make an exception with the axles though due to how light the car is.

On a seperate note, would it be possible to machine out the spot for pinion bearing in the 8in 3rd member to fit a larger bearing? If that's the only issue then maybe it would be worth machining it for less power loss?

I'm just trying to see what people have done before and what solutions there might be out there. Overall I think if I had to change things out it'd probably be an 8.8 just due to how much cheaper it is to get the housing and parts for it in for first place. But if I can reuse the 8in I think it would be better with less losses and less things I would have to buy/change out, as I know the 8.8 had a different way of mounting to the drive shaft.

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Availability is something to look at as well, I haven’t seen an 8 or 9 inch rear in a pick and pull for years. The places are littered with 8.8’s.

 

You won't have nearly as many gear ratio choices with an 8"

 

I'm currently doing a Model A with a FOX body 8.8". Perfect width to keep wheel close to the body.
The only downside I can see with them is the fact that the service cover isn't as "traditional" looking as a 9".
That being said I've raced stick shift FOX bodies for years (with 26 X 8.5) slicks and been high 10's and low 11's with high 1.40s 60FT and never had any issue with the stock 28 spline axles. We always used the Ranger 7.5" axles for the 5-lug conversion.
And like Budget36 said; the 8.8's are laying everywhere and can be had for a song.

 

Currie=$$$$$

 

I've done many 100's of 9 inch rears in the customer chassis I've built over the years, yet last year when we were up dating my 40 coupe I chose a Maverick 8 inch on CE parallel springs because it was the right width and the spring pads fit. I did this at the advise of a 40 guru from CA who has done this many times with no problems. The 40 is powered by a snotty little 327 with a 350 turbo and I felt that the 8 inch would be sufficient for me. I could have done a 9 inch but thought it was overkill for this build.

 

Having gone through this drill ‘last year’ (2020) to build an axle for my ‘37 Chevy project, let me share a few things to add to your considerations.

The beefiest common 8.8” axle housings are Explorer. 31 spline, 3.25” axle tube diameter, frequently LSD and commonly found with disc brakes (a model year thing). Pinion is offset.

The Ranger 8.8” housing is also pretty beefy, depending on year model, 56.5” or 58.5” WMS to WMS, 28 spline, 3” axle tubes, typically drum brakes, but may be 9” or 10” dia., depending on application. Pinion is offset. Ranger 7.5” and 8.8” axle shafts are the same dimensions.

Mustang 8.8”, not as beefy a housing as the others, but pinion is ‘centered’ using same length axles both sides. 28 spline, LSD common, 9” drum brakes thru ‘93 models, disc ‘94 up, the latter 2” wider overall. However, the ‘94 thru ‘98 uses the same width housing, but the disc brake axles are 1” longer per side and 5 lug.

I went thru the 8” vs 9” debate before deciding on the 8.8” version. Mostly because I had limited floor space in the 3rd member area and offset pinion played havoc with the driveshaft tunnel. My first choice was the Ranger 8.8” (58.5” width) but it has the same offset issues as the 8” & 9”.

I finally settled on using a ‘86/‘98 Mustang housing with two 5 lug same length Ranger axle shafts and rebuilt a limited slip 3.73 carrier and all new bearings etc. Did not have to narrow a housing, and am using Ranger 10” drum brakes. Though ‘lighter duty’ than other housing choices, I am using a warmed up Chevy 250” six in a light weight coupe and think it is plenty adequate for my particular build.

The 8.8” axle family offers a lot of variations, some leading to convenient mix and match combos. Now I don’t know what I am going to do with the 8” and 9” stuff I have had on the shelf all these years.

Ray

 

The 9" Ford rear axle is your strongest/cheapest rear axle option, at least in my area there are still plenty available. You have a much wider option of gear ratios, axle splines and other upgrades with the 9"axle. They are the most widely supported rear axle in the aftermarket plus they are easier to work on than the 8.8" and look a lot better in a Hot Rod. Being that they were first manufactured and used in 1957 they are also correct for a H.A.M.B. friendly era build.

 

@saltracer219... ..True enough, but the “Salisbury” style Spicer axles were used by Ford from about 1948 in F1 and Lincoln/Mercury (all models) and Ford wagons from ‘49. Many other applications of that style housing ‘59 up.

No argument about looks, however, but era pedigree for HAMB friendly builds seems to not be in question.

Ray

 

the 8" in my 47 coupe has endured a lot of abuse from the ZZ3/350, seems pretty stout to me.

 

If it is for the car that has the instrument cluster in your avatar, your likely candidate is a circa 1991 Ranger 8.8, due to the width.

Your stock axle is 56" wide. The Ranger axle in that age range is 56-1/2". If 28-spline axles are a worry, you can get alloy ones to swap in.

There are virtually no 9-inch rear axles in my area, save for the occasional private seller. I got the Ranger 8.8 that is under my first-gen Falcon for $100+tax.

I just sold my second-to-last 9" rear for $550.

 

My Nephew and I just swapped rears in his O/T F-150. He had an 8.8 with 2.73 gears and we found another 8.8 in a 4x4 at our local yard with 3.55 and a Limited Slip for $125. That’s cheaper than swapping gears, plus he got a Limited Slip. We resealed and replaced the axle shaft bearings, but everything else was fine. I love the nine for ease of gear swapping, and it’s what I used bracket racing, but the 8.8 is a great axle. Isn’t it funny that almost all of us use Ford axles no matter the make of engine?


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A few things:
1. We do not know where he is. Where I am, there are NO 9-inch rear ends in yards. There are hundreds of 8.8s, though.
2. He does not have a hot rod. He has a Falcon. If you can see the rear end, it is either on a lift, or he rolled it. If you want to lie belly down on the ground to see the bottom of the 8.8 in my Falcon just to pass judgement on me, have at it.
3. There is no native 56" wide 9". That would necessitate narrowing, and custom axles, even if he got the 9" for free, narrowing is not free, and neither are even cut-to-fix axle shafts. There goes any savings, even if there were any there to begin with. "and other upgrades with the 9"axle" add even more to the cost.
4. The 8.8, as has been mentioned, is a Salsbury-type axle, the use of which predates the 9", by nearly a decade by Ford.

 

@gimpyshotrods

looking at your Ranger axle, is there enough room to drill for 5x5.5 BP?
56.5 would be perfect for a project I have

 

Had an 8" in a 40 Buick with a healthy 350/350 with a shift kit, 3:00 gear, i beat the hell out of that car for years and never had any trouble with the rear. Never tried to hook it up though.

 

To add fuel to strength of an 8.8:

I used to do a lot of work for the 4x4 world. A common swap was a disc brake Explorer 8.8 into an XJ Jeep Cherokee.

The most common setup was 4.88:1 gears with 37" tires, or 5.13:1 gears with 40" tires. Not only did they hold up just fine to this level of configuration with stock axle shafts, they held up to the delivered torque.

Might not sound like much that a stock HO 4.0 6-Cylinder makes 235lb-ft or torque. Once that is sent through a 3.83:1 first gear, a 10.44:1, and the axle ratio (split 50% with the front axle), that is either 22,927.5lb-ft or 24,102lb-ft of torque. Keep in mind, that transfer case can be set to run the rear only, too!

If that is not enough, then by all means upgrade.

 

The pinion offset is an issue with the 8.8, but a lot of guys have found by buying another stock short-side axle and cutting down the tube on one side, that centers the pinion and gets you a good width for earlier cars.

Currie sells a '64-65 Mustang bare bolt-in 9" housing for $670 that will fit your Falcon but you'll still need to come up with a 9" third member. 64-65-mustang-replica-9-housing - Currie Enterprises

You can swap the 8" over to 31 spline axles, but it will cost almost as much as a beefed 9". The 28 spline axles are a definite weak point, I couldn't even begin to tell you how many I broke in a '58 Ford I used to own but power was a hopped-up FE and the car wasn't light.

Ford did semi-address the pinion bearings. The early ones (up through '65 IIRC) started having problems almost immediately so Ford did 'upgrade' the pinion bearings in the later versions. They helped, but basically didn't markedly improve the torque capacity but did mostly eliminate warranty issues. There is simply no way to install bigger bearings.

Ford discontinued the 8" and 9" due to high internal losses, particularly the 9". The original idea was to lower the driveshaft for lower floors, but dropping the pinion down lower on the ring gear reduced efficiency. When the OEMs started chasing fuel economy, something better was needed.

You will have to shorten your driveshaft with either a 9" or 8.8" swap or find one that fits.

Gear ratios are the other issue. 'Back in the day', finding 'performance' ratios for a 8" or 9" was difficult and expensive. 3.70 or lower was very hard to find, you could get 3.0 and 3.25 easily, 3.56 was a common ratio (although it was usually found in a WAR case and those would break... AMHIK... LOL) With OD trans now being standard on everything, the lower ratios are the common ones found now in the 8.8" but without a OD not all that 'freeway friendly'.

 

I'm not sure. I will check when I get to the shop. I have extra 8.8 axle shafts on the shelf.

Diameter aside, on that 8.8 (and maybe all) there are no extra holes in the axle flange, and it is machined on both sides. Re-drilling is a matter of a drill guide, or a good machinist.

My 8.8 is not 5-lug anymore. Since it is in a 6-cylinder Falcon, I re-drilled it to 4-lug.

 

Another thing worth mentioning: The wheel houses on a first-gen Falcon are quite narrow.

In order to put a 195/60-15, on a 15 x 7 wheel with 4-1/2 back-spacing, on a 56-1/2" wide Ranger axle, I had to build outer mini-tubs for clearance.

My point is, unless I put on drag slicks (and maybe not even then), there is no way to get this to hook well enough to damage an 8.8, or an 8, or a 9.

It is all about use-case context.

Also, on the driveshaft attachment issue: It is not different, in as much as there is an extra piece. On an 8 and 9, there is a u-joint yoke on the pinion. On the 8.8 there is a flange, to which a yoke is attached. This is the solution to u-joint caps falling off when the driveshaft is removed for service. There are two sizes, car and truck. The truck one is larger. It can be swapped for the car one, for more floor clearance.

 

The Lincoln Versailles had a 9"/w disc brakes. By no means as common as an 8.8, but they're out there.

 

8.8 Explorer, shortened on 1 side to center pinion. You got disc brakes and 31 spline axles.