8.75 or Ford 9”???

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Pinion Comparison - Quality Body Shop Drivetrain

Less all read from the Dr Diff web site about the 9”:
“Notice, the popular Ford 9″ uses the smallest pinion shaft of the bunch.” Referring to the full range of pinions in a picture comparing 741, 742, 489, 12 bolt 9” and Dana 60 I believe. Dr Diff is well respected in our community from what I see.

Lol! People use the 9” because they are cheap, plenty full and you can get parts everywhere. They are recreated by aftermarket companies by the dozen. Let’s look at it from another angle... the Ford 9” is no different in popularity than the small block Chevrolet and that’s being replaced by a LS motor. But you chose a MoPar, with a Mopar engine... not an LS or Chevrolet engine for a reason.

say what you want but 8-3/4 rears are top shelf in my book. And less weight than a Dana 60. I hope the OP understands I hope what ever rear axle he/she chooses for this monster engine they are building it is ultimately their choice and I wish them the best no matter what rear they chooses. And where are the pictures? All this text and not one picture?
Syleng1 out.
 
The 8 3/4 needs a bigger pinion shaft because it's supported on only one side of the ring gear. The ring has leverage pushing the pinion away from it.
 
I’ll say it again it NEEDS the pinion support on the end to deal with deflection because the inner and outer pinion bearings are a meer 1/2” apart. And they still fail at the “third” bearing. Tell the facts as they are.
 
Pinion Comparison - Quality Body Shop Drivetrain

Less all read from the Dr Diff web site about the 9”:
“Notice, the popular Ford 9″ uses the smallest pinion shaft of the bunch.” Referring to the full range of pinions in a picture comparing 741, 742, 489, 12 bolt 9” and Dana 60 I believe. Dr Diff is well respected in our community from what I see.

Lol! People use the 9” because they are cheap, plenty full and you can get parts everywhere. They are recreated by aftermarket companies by the dozen. Let’s look at it from another angle... the Ford 9” is no different in popularity than the small block Chevrolet and that’s being replaced by a LS motor. But you chose a MoPar, with a Mopar engine... not an LS or Chevrolet engine for a reason.

say what you want but 8-3/4 rears are top shelf in my book. And less weight than a Dana 60. I hope the OP understands I hope what ever rear axle he/she chooses for this monster engine they are building it is ultimately their choice and I wish them the best no matter what rear they chooses. And where are the pictures? All this text and not one picture?
Syleng1 out.

Yeah , wait till u start blowing an 8 3/4 every other week end , you`ll go to a dana 60 or a ford 9'' !

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So I'm going to ask the question how do you keep an 8 3/4 from breaking? I think Moser sells a new nodular case, but I don't know how much stronger it is. I would love to stay 8 3/4 in the Dart, but I'm concerned with a stout big block and trans brake that it will break the differential.
 
I kinda go by what a brilliant mopar maven, Monte Smith said about 8 3/4. He said, basically and paraphrased, the 8 3/4 case is the weak point, allowing the ring to walk away from the pinion, and shear teeth. At what point that happens, depends on the parts involved ( nodular case and spool, or stock case and sg, etc.) Bracing the housing can help, just like it does with a nine, but the case is the weak point. The nine now has a bunch of much stronger cases than stock, but the original 9" grey iron cases were certainly no better than an 8 3/4 case, thats why original nodular ford cases were so prized/expensive.
I have had no problems with a 500hp 440 in a b-body with my 8 3/4, using slicks and a 4000 converter. But i still have stock axles, and rather than put lots more money in my 8 3/4, i would put in a dana.
If you are looking at 600 hp with a stick, or transbrake, personally i would step up to a dana or nine. The money spent to upgrade a 8 3/4 to handle that power would be better spent on something else.
 
I kinda go by what a brilliant mopar maven, Monte Smith said about 8 3/4. He said, basically and paraphrased, the 8 3/4 case is the weak point, allowing the ring to walk away from the pinion, and shear teeth. At what point that happens, depends on the parts involved ( nodular case and spool, or stock case and sg, etc.) Bracing the housing can help, just like it does with a nine, but the case is the weak point. The nine now has a bunch of much stronger cases than stock, but the original 9" grey iron cases were certainly no better than an 8 3/4 case, thats why original nodular ford cases were so prized/expensive.
I have had no problems with a 500hp 440 in a b-body with my 8 3/4, using slicks and a 4000 converter. But i still have stock axles, and rather than put lots more money in my 8 3/4, i would put in a dana.
If you are looking at 600 hp with a stick, or transbrake, personally i would step up to a dana or nine. The money spent to upgrade a 8 3/4 to handle that power would be better spent on something else.
That's what I figured. I hate to, but I think it would be the best thing to do and save that 8 3/4 A body housing for the Valiant. It will be a decent street machine, but not crazy hp or slicks either.
 
The only reason Chrysler used the Dana 60 behind the Hemi and the six pack bb cars was because Ford wouldn't sell them any NINES.
 
People seem to forget that the average nine was.....average. Ford built a lot of nines with gray iron centers, open gears, and 28 spline axles. An 8 3/4 was a better rear, in stock form. But ford also offered nodular cases and bearing retainers, decent limited slip (not great though, nowhere near as good as the clutch dana units) and 31 spline axles. That made the nine as good or better than the 8 3/4. Then since nines became preferred in nascar for easy gear changes, more ratios and stronger parts yet were developed. So now the nine has lots more parts and ratio selection, and can be as strong as your wallet will allow. That is not true for an 8 3/4 or a dana.
 
Ya, that 28 spline axle in the nine is the same strength as the 28sp in the four cylinder mustang 7.5. But the Explorer 31 spline 8.8 is the goto rear end anymore with cost and availability.
 
People seem to forget that the average nine was.....average. Ford built a lot of nines with gray iron centers, open gears, and 28 spline axles. An 8 3/4 was a better rear, in stock form. But ford also offered nodular cases and bearing retainers, decent limited slip (not great though, nowhere near as good as the clutch dana units) and 31 spline axles. That made the nine as good or better than the 8 3/4. Then since nines became preferred in nascar for easy gear changes, more ratios and stronger parts yet were developed. So now the nine has lots more parts and ratio selection, and can be as strong as your wallet will allow. That is not true for an 8 3/4 or a dana.

I've never seen a factory Detroit Locker in an 8 3/4. They put plenty of um in 9s though.
 
I've never seen a factory Detroit Locker in an 8 3/4. They put plenty of um in 9s though.
Agree. I think ford used the locker cause there isnt a lot of room in the case for a decent posi, due to the third pinion bearing. Ive got a detroit locker in my 8 3/4, but it sure aint factory! Lots of factory nine lockers in boss and cobra jet cars, (though the cj ranchero i had, had a 3.25 open!)
 
I've also never seen a Ford truck 9" that had anything less than 28 spline axles. There may have been some, but I ain't seen one yet, and I've been through a PILE of 9s. Mine is a 31 spline out from under a 74 F100.
 
Agree. I think ford used the locker cause there isnt a lot of room in the case for a decent posi, due to the third pinion bearing. Ive got a detroit locker in my 8 3/4, but it sure aint factory! Lots of factory nine lockers in boss and cobra jet cars, (though the cj ranchero i had, had a 3.25 open!)

You could well be right. That's a good point. I think they are really close in strength. But still the 9 inch is cheaper to build......unless you find a good dude like Roy that will sell them fair. I was real fortunate with the 9 inch I have. One of my customers at work just walked up and said "Hey Rusty, you want a Ford 9 inch for free? Come get" so I did. LOL
 
You could well be right. That's a good point. I think they are really close in strength. But still the 9 inch is cheaper to build......unless you find a good dude like Roy that will sell them fair. I was real fortunate with the 9 inch I have. One of my customers at work just walked up and said "Hey Rusty, you want a Ford 9 inch for free? Come get" so I did. LOL
Free is ALWAYS the right price!
I had a couple of friends in the rearend business, that used to scrounge rearends out of the boneyards, back when not everyhting was fwd. They specialized in the nines (they were both ford lovers) but would snag anything they could malke a profit on, or had a buyer for. They taught me the ins and outs of the nine, what to get, and what was neccessary to make them live , cause they built them for the local racers. Kinda why i am partial to the nine, i guess. They did get me a great price on my 8 3/4 locker, and put it together for me too.
It is a shame, one has retired, and quit racing, and the other passed young from pancreatic cancer. I sure hope i dont go THAT way!
 
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Free is ALWAYS the right price!

Dang right! It has some HUGE brakes on it too. 11" at least. I ain't measured um. It's a highway gear right now and it's probably gonna get left in for a little while. With a mild 400 though, it may pull it well enough to leave it in there. My plan was for a 3.89 but "we'll see".
 
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