why a Ford 9"?

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72goldduster

72goldduster

Mopar Kid
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DEFINITELY NOT TRYING TO OFFEND ANYONE WHO CHOSE ONE, but what are your reasons for it? the 8 3/4 is much stronger, has bigger everything (except of course, the ring gear diameter, and in the 741 case the pinion diameter). again, not trying to get anyone hot headed, I'm just wondering what made you choose a 9" instead of the tried and true 8 3/4"
 
Ford 9s were/are the choice of drag racers that might want to change the gear ratio quickly from one track to another, 1/4 mile 1/8 mile, lighter and much less rolling friction and plenty of em around .
 
the67fish said:
Ford 9s were/are the choice of drag racers that might want to change the gear ratio quickly from one track to another, 1/4 mile 1/8 mile, lighter and much less rolling friction and plenty of em around .
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I thought the Ford rear ends had more resistance than the Chrysler ones... also isn't the carrier interchangeable on 8 3/4s too?
 
MOPEkidD-3 said:
I thought the Ford rear ends had more resistance than the Chrysler ones... also isn't the carrier interchangeable on 8 3/4s too?
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yeah. I was just doing some research and it seems to me the numbers that count (bearing size, pinion size, etc.) favor the 8 3/4". made me wonder. one thing the nine has to its advantage is the cost and availability. Ford's main concern, it would seem, was production numbers.
 
The only reason why I used one is because I couldn't find a decent 8 3/4 around here and I already had a 9", detroit locker and gear set for a different project. I also took advantage of using the rear disc brakes from an 8.8 axle.

New dart2.jpg
 
Yes the 8 3/4 is a hard item to find in my area,if I couldn,t find one I would have gone with a Ford 9 inch for availability purposes.
 
To play devils advocate, there are a lot more gear ratios available for the Ford 9".

That said, I have 5 different 8 3/4's, and every type of 3rd member. And not a single Ford 9.
 
Me personally Id hunt down a Dana in a truck and have it narrowed. Lots of those Dana's in Ford trucks :snakeman:.

Seems like more money that way but you'd get a grenade proof rear axle..
 
Yup, people use them because they are generally cheaper and abundant. I won't.

The 8.75" rear is stronger than the ford 9" in stock form and, contrary to popular belief, the 9" is a copy of the 8.75"! There is a ton of aftermarket stuff for them to make them better. Most of that stuff is not required for a 8.75". How strong is a 8.75"? The TF727 equipped 68 SS Hemi Barracudas had them and ran mid to low 10's in 68. They are currently sub 9 second cars!
You can even get an aluminum case for the 8.75" now. Very nice and even stronger than the iron case. $$$$$$$$$$$$:headbang:
 
72goldduster said:
DEFINITELY NOT TRYING TO OFFEND ANYONE WHO CHOSE ONE, but what are your reasons for it? the 8 3/4 is much stronger, has bigger everything (except of course, the ring gear diameter, and in the 741 case the pinion diameter). again, not trying to get anyone hot headed, I'm just wondering what made you choose a 9" instead of the tried and true 8 3/4"
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Hmm. 8 3/4 much stronger? There are legions of drag racers out there that would beg to differ. History is not on your side here and the opposite is more likely to be true.

8 3/4 has bigger (almost) everything? No contest to the pinion diameter, but the Ford 31 spline axles are superior to the 29 spline Mopar axles. 9" is bigger than 8 3/4 inch although some Ford 9 " rings measure 8 3/4. The 8 3/4 pinion in the 489 case is actually bigger than the Dana 60 pinion. (1 7/8 vs. 1.626.) Interesting that the Ford 8.8" shares the 1.626 pinion size with the Dana 60.

Some of the other comments thrown out here are also worth mentioning. Ford 9" a copy of the Mopar 8 3/4"? Both introduced in 1957. Nothing to see here folks, move along. Rolling resistance? The small Ford pinion is the only factor likely to make a difference here and that would be in Ford's favour. I suspect most users would not detect the difference.

Keep your Mopar all Mopar? Definately a point to the 8 3/4. Still, the Dana 60 is the "ultimate" Mopar rear end and a common source for Dana 60 housings would be 3/4 ton Ford trucks. Hmmm...

I would not go out of my way to put an 8 3/4 under my Cuda, Reason is the high cost, poor availability, and 4" bolt circle of the A body piece. The 8.25 found in 73 and later A bodies is a bolt in, has the LBP and is plenty strong for street use. If I was to use a non mopar axle, I would be looking seriously at the Exploder axle. Best wow factor is, of course the Dana 60. I might just modify a Ford truck piece with LBP axles and try to pass it off as Mopar!
 
the67fish said:
Ford 9s were/are the choice of drag racers that might want to change the gear ratio quickly from one track to another, 1/4 mile 1/8 mile, lighter and much less rolling friction and plenty of em around .
Click to expand...

The center section can be changed out in less then half an hour on a 8 3/4 we do it all the time..the 9 inch is no better then an 8 3/4 performance wise plenty of guys running in the 9's with out a lot of money in them..by the way NO ONE i know uses one of those turd rearends in their mopars that i know..its either 8 3/4 or dana...
 
The main reason they are used is because, as my buddy used to say about Chevys, "everybody runs 'em because everybody runs 'em." When they are readily available the price goes down. Two important factors when trying to build a fast car. Then the more people that use them the cheaper replacement or upgrade parts become. I know that I could go to the local wrecking yard today and get a Ford 9" to haul home. I doubt that I could find a 8-3/4 available in the state!
 
As I recall, the 9" has an additional bearing to support the pinion?
There was a magazine article a while back, that discussed the difference. The 8 3/4 was right there in all aspects, with the exception of the additional bearing (I thought it was to support the pinion?)
 
A few years ago I read an article in one of the camaro lover's mag. on the strenth of the factory rear diffs. as I remember the dana 60 was rated the highest( a couple of hundred h.p. over the rest). The part that shocked me the most was the 83/4 and the chevy 12 bolt were rated for 500+ h.p. stock, the 9 inch ford was rated for up to 400h.p. stock. Out of all the rear axles the 9 inch is by far the easyes to set up and very strong when put to gether with expensive after market parts. what I have seen at the track is when they fail the cause is usualy the pinion support blowing out the front of the case(witch I am told is thing that makes them stronger). The 8 3/4 has 30 spline axles and the magority of 9's have 28 spline only the heavy duty axles had 31, traction loc diff. is famous for its one legged burn outs, so a locker is the way to go(more money). Dana 60 came in all 3/4 and 1 ton Dodge trucks up to around 2001.
 
The link posted earlier states the 8 3/4 uses 29 spline axles. Ford axles were 28 or 31 spline and the 31 spline axles tend to be later model as opposed to any intentional use as heavy duty. Still, more splines = better and I'm sure the Ford engineers knew this. At any rate, change the side gears and add custom axles and you can pretty much get whatever you want, but I'm thinking along OEM lines here.

One application specific item with an A body is gas tank clearance. I'm pretty sure I read somewhere that the 9" Ford in an A body creates some hassles here as does the Dana 60. 8 3/4, 8.25 and 7.25 fit no problems.
 
Gryzynx, the 9" has an extra bearing to support it because it NEEDS it! LOL


Your spline count info is incorrect. I know, I own an original 69 dart swinger 340 4speed car w/8.75" rear end. It came with 30 spline axles from the factory.
Here's a replacement axle, for example:
http://www.ringpinion.com/ProductDetails.aspx?ProdID=5639

The gear selection argument is laughable. Exactly WHAT gear do ya NEED that's not available?

Even a 741 case is stronger than a 9"!!!

Get the FACTS!!!
http://www.dippy.org/forum2/index.php/topic,84.0.html

•''741' Casting - 1 3/8" (1.375") Small Stem Pinion.
Carrier casting numbers were 1820657 (1957-1964) and 2070741 (1964-1972). This unit was usually used in low weight/medium horsepower and high weight/low horsepower applications. Although it is the weakest of the 8.75" units, it is still a stout unit, and is stronger than the Spicer-built Chrysler 8.25" rear. The 1 3/8" pinion is also larger than the pinion in the Ford 9" rear.•''742' Casting - 1 3/4" (1.75") Large Stem Pinion.Carrier casting numbers were 1634985 (1957-1964) and 2070742 (~1961-1969). This assembly was replaced by a phase-in of the 1-7/8" pinion '489' casting starting in the 1969 model year. This assembly was typically used in high weight/medium horsepower applications through high weight/high horsepower applications. Although not generally considered to be stronger then the '489' carrier, the '742' carrier is extremely stout, and is favored by many Mopar enthusiasts because they are easier to set up. Noted Mopar enthusiast John Kunkel mentioned that the biggest advantage of the 742 carrier is that it has the largest rear pinion bearing of all the 8 3/4" carriers. The larger bearing helps to prevent pinion deflection better under a load than the others.
•'489' Casting - 1-7/8" (1.875") Tapered Stem Pinion Carrier casting numbers were 2881488 or 2881489 (1969-1974). This assembly was introduced in 1969 and was phased-in to relace the 1-3/4" pinion '742' unit through 1970. Note: the 1-3/4" pinion also appeared in some '489' carriers during this period. By 1973, the '489' was the only unit available in passenger car applications, and was typically used in high weight/medium horsepower applications through high weight/high horsepower applications. This carrier is considered to be the strongest by some Mopar enthusiasts. Because it requires a crush sleeve to set bearing preload, some Mopar enthusiasts prefer the '742' casting. This is not really an issue now because there are now parts available to eliminate the crush sleeve.
 
Here my reason for not using a 9". Because it's a Ford unit,lol!!!
 
No matter how you slice it, the fight is over and the 9" won.

I love how the Mopar and Chevy side of the debate comes down to pinion diameter. Who ever broke a pinion shaft? LOL

If it doesn't break, smaller and lighter is a good thing.

I've got an 8.75 in my car, but I could have probably had a new 9" for less money. $500 for a 40 year old rusty stock housing? Really?

Steve
 
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