And the reason they now make a 9" center section that uses 12 bolt gear set up. My 34 Ford had a rear axle out of one of the 49-56 Fords. Replaced with a 9" a couple of years ago.
Interesting post. How many of you install a nine inch cause thats what goes in a hot rod? I've had many an argument over whether a nine inch is necessary, and always the guy who wants one says yes, because he thinks he has some power under the hood. In the average square bodied hot rod, the answer is no, the car is light enough that there isn't enough traction in a street car to ever break a rear end. Just removed a nice 8 inch from a model a coupe in favour of a nine inch cause the owner was so convinced that his warmed up W motor (409), would break the 8 inch. I'll give that a nine inch looks the part, but if you're on a budget, not necessary.
I haven't ever seen a 9" in a survivor rod either. Lotsa 55-57 Chevy rears though. But there's no reason there couldn't have been some 9" used back in the day. I put a 9" from a '61 in my Model A and also stuck in a Y-block. I like to think that if it had been built back in 1962 the builder woulda went to a junkyard and salvaged the engine/trans/rear out of the same car Ford.
Up until '49, Ford used non-hypoid rear axles, as did others. When cars started getting lower, manufacturers switched to hypoid designs as this would allow them to reduce the height of the driveshaft tunnel inside the car. In '57 when the 9" came out, Ford had increased the hypoid angle yet again to get still-lower floors. Hypoid designs reduce efficiency; the larger the angle/lower the pinion gear on the ring gear, the more that was lost. This also allowed for increased gear deflection for a variety of reasons, which was bad. Ford solved this by adding a third pinion bearing on the end of the pinion gear which reduced deflection to where there was less than even the non-hypoid axles could manage. Once the strength issues in the main castings was worked out (better pinion supports, 'N' cases, etc), the 9" became the rear axle of choice for racers as it offered strength equal to the larger axles like the Dana 60 with considerably less weight yet allowed easy gear changes by simply swapping pumpkins. Even the current nitro cars use a rear axle based on the 9" design because of it's superior strength. The cost was a slight loss in efficiency. I don't recall the exact numbers, but the 9" was about 1.5% less efficient compared to rears with less extreme hypoid angles. This didn't matter for years, but when fuel economy standards came in it became important as the manufacturers were looking for every last bit they could find. Ford designed the 8.8 rear, which while it didn't offer the same ultimate strength of the 9" or the convenience of easy gear changes, did have better efficiency and the 9" disappeared from Ford production.
The 9" is 10% less efficient than an 8.8. That doesn't equate into a direct 10% fuel loss. Most cars require somewhere from 6 to 12 hp. to operate at road speed such as 65mph. That percentage is a multiplier in the equation.
Once open drivelines were common, the Hotchkiss axles became popular (9" Ford, 8" Ford, Olds/Pontiac, and the 55-6? chevies). Olds were popular with the Gassers, etc. Primarily due to their huge axle shafts. 32 spline IIRC. Chevies were popular with the street rod crowd through the 60s and 70s. But with their tapered axles, they were known for twisting or breaking. The thing that made the 9" popular with racers is strength. They have an extra bearing on the Pinion, just inside of the ring gear. So the pinion is supported on both sides of the ring. This is also what causes them to have more drag than the later Salisbery design. Of course, any of the Hotchkiss axles can be a good choice because they are the poor man's quickchange. It's a lot easier to have whole pigs set up and ready with different ratios to change out on race day. Even with the semi-floaters, it's easier to just pop the axles out and change the pig. Another factor is that Hotchkiss axles were considered "safety axles. The axles are held in at the wheel bearing. No C-clips. So if an axle breaks, the wheel is less likely to depart the vehicle.
Correct. To put it into perspective, if a 8.8 rear consumed 1 HP going down the road, a 9" would use 1.1 HP. Given all the other losses (transmission, engine-driven accessories), it was a pretty small component in terms of overall efficiency.
The only reason I am changing from a 12 bolt to the 9 inch Ford, is that the 12 inch rear end needs to be narrowed anyway, and I have a 9 inch in the yard that I can do all the work on without parking the truck. I like both equally, but the most significant advantages of the 9 inch rear for me are, larger 31 spline axles, I can pull the pumpkin if work is necessary, and the big bearings at the wheels. I am going to be running 3.73 Eaton gears. Bob
I snagged a 9” out of an old bronco years ago before they became popular. I got a good deal and it fits perfectly in my 1940 ford coupe.
All depends on application and depth of your pockets. I collect everything so I have a mixture of GM 12 bolt,GM 10 bolt, 9" and Mopar 8 3/4. To coin hrp's thread title "everyone likes a nice rear end "
I actually have an 8” in my rod currently and was trying to figure out if I really can justify buying and rebuilding a 9” or run the 8” with my sbc that should have about 300-400 hp? Sent from my iPhone using The H.A.M.B. mobile app
Thanks Steve. It hardly seems worth it for 0.1%. I have a 9" but I'm not really fond of it. I've not had any trouble breaking anything, but it leaks everywhere, all the time.
I got my 1957 Ford rear out of a 1957 312 stick Ranchero. Nice and narrow for a hot rod without narrowing it. I think it was the narrowest stock rear. Early Olds was a bolt in, in a 55 Chevy.
Just thinking about it a bit. Years ago I helped a buddy with a 12 Bolt Posi that he somehow destroyed at the drags and it was pull the whole housing out of the car, haul it to a shop that did rear end work and wait a week until it was rebuilt so we could put it back in. A few years later I helped another buddy swap third members in a 9 inch that he had broken in a street race in a store/mall parking lot in a little over an hour. He had gotten the car off the street into the parking lot, got to a pay phone ( it was that long ago) called me to come get him and run him home to pick up another third member and the other things we needed and back we went. No tow bill and no big shop bill before he could drive it. Big tab later when he built another third member for it though. As far as when nine inch rears really came into general use. I'd have to agree that after the big Olds and Pontiac rears got too hard to find. That and for racing them you always had to change gears rather than sort though truck rears in the wrecking yard for the desired ratio..
First hot rod I built got a Ford 9" and I didn't know what one was. I needed an axle of a certain width, with 4 1/2" 5 bolt wheels, and found one in a junkyard 58 Ford station wagon. I figured a station wagon would have a strong rear axle, I was running an Olds 371. This was about 1970. Years later I heard about the Ford 9" being the hot setup and figured out that's what I had used.
I got mine the easy way. Had the factory unit shortened 3/4 per, added big bearing ends, Timken open wheel bearings, disc brakes, 31 spline axles, Yukon trac-loc, 3.50 gears for highway cruising, and a 1" taller yoke to make my aluminum driveshaft perfect fit. 300hp, overdrive, the 3.50s get me 24.5 mpg! Sinister Racecraft in Amarillo did the mods on the rear. I did talk to a shop just south of the D/FW area that told me he had over 1800 9" units in their yard if I needed one
Advantages to a 9" strong pinion design 3 bearing instead of 2 , one carrier series for all ratios ,swapping 3rd members to change ratios, inclosed spider gears so if you break one you do not take out the ring gear.
I had been waiting for somebody to say this. I know a lot of cars at least started out with a driveline from one the same car. Also some circle track guys called a 9" a poor mans quick change.
Never lost an axle and tire in any of my Ford circle track cars with a 9". Saw a lot of left rear Chevy axles depart the vehicle in the turns.
I run the same rear in my t-bucket, Henry J and I just put one in my 57 p/u yesterday, perfect width. I have a Lincoln Versailles 9 inch in my 41 p/u which is also the same width.
The 1957 through 1959 Ford rearends are a perfect setup for the hot rodders but are getting scarce these days for sure!
I'm old, back in the day, the only 9" rears seen were in Ford products that came with them. The Olds/Pontiac 9.3 was the preferred rear swap, some Dana 60's, some Chrysler 8 3/4's, some GM 12 bolts, in drag and hot street cars, 55-64 Chevy's in street rods. I never remember seeing a 9" installed in anything other than stock Fords in the 60's-70's. The 9" began to show up in the late 70's and early 80's when the supply of older rear ends became in shorter supply. The long production run of the 9", simple design, coupled with the aftermarket support , guaranteed it's success.
I have some 9" Ford rear-end Tech over on my blog https://greaseralley.com/2013/06/11/ford-9-inch-tech/ that has really good info on how to identify 9" centers, "N" cases vs "WAR" cases and housing info. If you guys are interested check it out.
It was written that 9" Ford rear ends were discontinued because of excessive power loss of extreme angle hypoid gears. That power loss (energy loss) is the transformation of mechanical energy to thermal energy (energy of heat). Energy is never consumed, it simply changes form. I feel correct lube minimizes this problem. I feel, with no proof, that Ford switched to the Dana style non removable center section to reduce mfg costs. Greg
Looks like most of the Greaser Alley stuff is copied and pasted from the Kevinstang site, with no acknowledgement so far as I see. http://kevinstang.com/Ninecase.htm
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