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No worries... Still looking for a ff hp60...
 

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This article compares stock shafts, and it doesn't have the Hi 9. 35 spline front hi9 is stronger than a 35 spline hp 60


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Interesting Chad. I saw that they both had the 35 splines....

I understand that the Currie HP 60 offers the best clearance of any HP60, I wonder how much more clearance you get with the 9.

Both are bad ass axles for sure... and it may be a toss up on the two.

Interested to hear more about the 35 spline differences.

I may shoot Currie a note and see what they say.
 

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I think you would see jeeps that get jumped running 9s more often because an aftermarket 9 can be trussed differently than a 60. I believe the Currie 9s are lighter than the Currie 60s.

The other thing that I have read is that the ring and gear contact pattern may be better on a 9 than a 60, but I don't know this for sure.
 

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I think you would see jeeps that get jumped running 9s more often because an aftermarket 9 can be trussed differently than a 60. I believe the Currie 9s are lighter than the Currie 60s.

The other thing that I have read is that the ring and gear contact pattern may be better on a 9 than a 60, but I don't know this for sure.
The gear deflection on the hi9 is basically 0 when ran in front , and on a low9 when ran in rear, making the R&P stronger than a 60


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The currie high nine 3rd member uses ford 8.8 gear. And does not have the front pinion support bearing of a normal 9 inch. Check true high 9 it cost alittle more the the currie set up but you actualy get an 9 inch ring gear.

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I've been researching 9" axles for a while now and to be honest they're pretty hard to beat...impossible to beat pound for pound. Maybe I am overstepping my bounds for my first non "welcome room" post, but here's what I've learned...

The best part about 9 inchers is the bad ass gears. Due to the design and thickness of 9" gear teeth, the gears actually become stronger and gain contact area as you go deeper (unlike Dana axles that tend to get weaker the lower you gear). The 9" ring and pinion will have almost 3 full teeth in contact with each other while a high pinion 60 has less than 2.



The top pic is a 9" R&P (5.14 ratio), the bottom is a HP60 R&P (5.13). These pictures are from the True Hi9 website, but the 9 inch gear contact pattern is identical on the equivalent ratio of LP gears.

Here they are from the top for better comparison of tooth size. 9 is on the left. HP60 right.

Anyhow all this comes at a price though. To get this much tooth engagement the pinion has to be offset from center quite a bit more than a HP 60. The 9" pinion is 2.25" above or below the ring gear centerline. HP60 offset is 1.125"
Not that big of a deal unless you're talking a low pinion 9, in which case the yoke's gonna be getting friendly with mother nature. But that problem is easily solved by a pinion guard just like everyone slaps on their 14 bolts.

I would avoid the Currie high pinion 9 case altogether. Like joeglock said, it uses a Ford 8.8 gear which isn't exactly a disaster, but if you're dropping the money to build a 609 skimping on the component that makes the axle unique and worthwhile seems like a waste to me.

If you are going to put a 9 in the front, seriously look into True Hi9. It's worth the money. You run the gear on the drive side and its KOH tough. For the rear, stick to low pinion. LP 9's have been proven in every facet of motorsports to kick ass. And for a not that much money you can run Ford Sterling or 14 Bolt outers and make on hell of a tough axle that doesn't tip the scales at 350 lbs.

The fabricated housing's available for 9's are going to be stronger than the iron center sections of HP60's and will come in a little less obese. How much lighter is anyone's guess, it depends on your choice of knuckles and how much you plan to truss the housing, etc etc.

And one final consideration...if ARB's are your end game, be aware that the 35 spline RD99 has a reputation for failing. There's fixes available, but nothing is certain, and the less than 2mm of sidegear engagement will always be weak, no matter if its chromoly or not. In the rear of a 5000lb JKU, wheel hop will wreak havoc on that little guy. Conservative driving and smart lines will extend its life but what the point of beef if you can't beat it like Rocky? In the front, it will be just fine.

Honestly, 9's are the shit no matter your locker choice, you just have to pay attention with an ARB and avoid crash locking...TrueHi9 front, LP rear.
 

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Currie F9 housings and all fabricated 9" housings (Spidertrax, Diamond, Ruff Stuff, Tubeworks, Dirt Tech, etc) share the same stud pattern and can bolt up to any standard 9" third members like a Strange or a Yukon.
Ok, thats what I thought. So its just Curries 3rd member that should be avoided as it uses the 8.8RG? I'm running a Currie RJ60 in the rear. Im thinking I'm going to go with an F9 in the front. I realize the gear ratios will be off slightly, but I don't think it will be a problem and I talked to a tech at Currie and he agreed that it shouldn't be an issue.

Do you know of any fixes for the ARB's on those? I have an ARB in the rear and would really like to go that route in the front as well. Hopefully by the time I come up with the $$ to do a front axle ARB will have some of the issues fixed.
 

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Currie's HIGH PINION third member is the only one that uses the 8.8. They contract with Strange Engineering (I think) to produce a low pinion case that accepts the across the board standard 9" gears. Ford occasionally dropped a tooth out of their ring gear to create better engagement, that's why they have those funky ratios like 4.86, 5.14, and 5.43s. I can't remember the margin percentage but I think numerically it is +/- 0.04 on the ratio. So if you keep 4.88 like your sig says, you should be fine with anything from 4.84 to 4.92....but I'm no expert, so make sure you double check that one with a non-web wheeler like me lol.

I talked to an old ARB tech and he has had a lot of luck extending the life of the RD99 by running bigger gauge airline and a higher PSI than ARB directions recommend. Somewhere in the 150PSI range depending on your setup. He told me a lot of failures he saw were from crimped air lines, which doesn't let the collar engage fully or lets it slip out and then they slip and grind each other to holy hell.

And then there's a few ways to beef it up mechanically. Spidertrax and Beyond Insanity make upgraded 4340 Chromoly engagement collars. These are the same shape as the stock ARB collar, just made of 4340. Here's the Beyond Insanity one installed...

They're both around 200 bucks + install price (unless you do it yourself). Not too bad.

Then there's the Ashcroft upgrade. Ashcroft Transmissions is UK company and they have put together a pretty savage upgrade. They rework the end cap, piston, locking ring, and change out the return springs.
LOCKED:

UNLOCKED:

End cap and piston:

Locking ring in end cap:


Compare that to the standard style locking collar from above and you can see they did some serious reworking. But it costs a minimum of 500 dollars and involves shipping a 40lb ARB to the UK. Are we really that hardcore? This seems like overkill to me and is best left for racers. The effort, downtime, and shipping hassles really seem to outweigh the benefits for a weekend wheeler. And to be honest I am not sure how proven it is. It didn't get much attention on pirate, but even the best stuff from the UK doesn't make waves here so who knows. Next time I talk to the guy I'm buying my 9" from I will see what his opinion of this one is and will post it here if any one is curious.

It would be nice if ARB would fix this, they have acknowledged there is a weakness, but last I heard they have no plans to alter the locker. They don't feel it would be cost effective. I read that it shares some features with a D44 RD109, making it easy to produce. Changing it to use a bunch of unique parts would cause a price bump I guess. But I'm not too clear on the details there. All I know is that we shouldn't expect any changes to come from ARB. The design flaw isn't so much a flaw as it is a limitation. The 9" diff is only so big, they couldn't squeeze any more engagement out of the case.
 

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Currie's HIGH PINION third member is the only one that uses the 8.8. They contract with Strange Engineering (I think) to produce a low pinion case that accepts the across the board standard 9" gears. Ford occasionally dropped a tooth out of their ring gear to create better engagement, that's why they have those funky ratios like 4.86, 5.14, and 5.43s. I can't remember the margin percentage but I think numerically it is +/- 0.04 on the ratio. So if you keep 4.88 like your sig says, you should be fine with anything from 4.84 to 4.92....but I'm no expert, so make sure you double check that one with a non-web wheeler like me lol.

I talked to an old ARB tech and he has had a lot of luck extending the life of the RD99 by running bigger gauge airline and a higher PSI than ARB directions recommend. Somewhere in the 150PSI range depending on your setup. He told me a lot of failures he saw were from crimped air lines, which doesn't let the collar engage fully or lets it slip out and then they slip and grind each other to holy hell.

And then there's a few ways to beef it up mechanically. Spidertrax and Beyond Insanity make upgraded 4340 Chromoly engagement collars. These are the same shape as the stock ARB collar, just made of 4340. Here's the Beyond Insanity one installed...

They're both around 200 bucks + install price (unless you do it yourself). Not too bad.

Then there's the Ashcroft upgrade. Ashcroft Transmissions is UK company and they have put together a pretty savage upgrade. They rework the end cap, piston, locking ring, and change out the return springs.
LOCKED:

UNLOCKED:

End cap and piston:

Locking ring in end cap:


Compare that to the standard style locking collar from above and you can see they did some serious reworking. But it costs a minimum of 500 dollars and involves shipping a 40lb ARB to the UK. Are we really that hardcore? This seems like overkill to me and is best left for racers. The effort, downtime, and shipping hassles really seem to outweigh the benefits for a weekend wheeler. And to be honest I am not sure how proven it is. It didn't get much attention on pirate, but even the best stuff from the UK doesn't make waves here so who knows. Next time I talk to the guy I'm buying my 9" from I will see what his opinion of this one is and will post it here if any one is curious.

It would be nice if ARB would fix this, they have acknowledged there is a weakness, but last I heard they have no plans to alter the locker. They don't feel it would be cost effective. I read that it shares some features with a D44 RD109, making it easy to produce. Changing it to use a bunch of unique parts would cause a price bump I guess. But I'm not too clear on the details there. All I know is that we shouldn't expect any changes to come from ARB. The design flaw isn't so much a flaw as it is a limitation. The 9" diff is only so big, they couldn't squeeze any more engagement out of the case.
Yeah thats the way I understood it to be on the ratios too. As long as you're in the next closest number up or down you should be ok. And seeing as I'm probably never going to be in 4wd on pavement anyways (unless I go up to the mountains and have trouble in snow) It really shouldn't be an issue (Ill also have manual hubs when I do the front axle).

Thanks for all the info. So its better to run ARB's at a higher PSI? i thought that would blow out seals? And larger line to the locker is against what ARB recommends because they say it takes up way more air (which makes sense) and there may not be enough air to keep pressure with a larger line, especially if you need lock the locker several times in a short period. I don't think I'd have a problem with that as I have a Kilby OBA with a 2.5gal tank but it still seems inefficient to run larger line. I don't see the benefit there.

I like the looks of those upgrade kits. I'll have to see what my options are when I'm ready to do this mod. And I wouldn't put it past Currie to do an upgrade. They already upgraded their D60 lockers in the last year or so. So it is possible. (I talked to an ARB rep on that...came up in convo when discussing an issue I was having).
 

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Yeah thats the way I understood it to be on the ratios too. As long as you're in the next closest number up or down you should be ok. And seeing as I'm probably never going to be in 4wd on pavement anyways (unless I go up to the mountains and have trouble in snow) It really shouldn't be an issue (Ill also have manual hubs when I do the front axle).

Thanks for all the info. So its better to run ARB's at a higher PSI? i thought that would blow out seals? And larger line to the locker is against what ARB recommends because they say it takes up way more air (which makes sense) and there may not be enough air to keep pressure with a larger line, especially if you need lock the locker several times in a short period. I don't think I'd have a problem with that as I have a Kilby OBA with a 2.5gal tank but it still seems inefficient to run larger line. I don't see the benefit there.

I like the looks of those upgrade kits. I'll have to see what my options are when I'm ready to do this mod. And I wouldn't put it past Currie to do an upgrade. They already upgraded their D60 lockers in the last year or so. So it is possible. (I talked to an ARB rep on that...came up in convo when discussing an issue I was having).
I thought the same thing you did but a lot of guys have been upping their pressure without blowing seals. I imagine if you push it up to the 200 range you could get in hot water but there's been a lot of success with this method. I think the idea is to keep as much pressure on the collar to keep it locked and prevent it from walking back under load and becoming partially disengaged.

As for running a larger line I don't remember exactly how much larger, and the I think the idea was to prevent the line from getting pinched closed during 3rd removals servicing. Beyond that I don't know the reasoning, but I know if done right there is no problem with efficiency. I will get some more info on this next chance I get and I'll post it up.

I think with a chromoly collar and smart locking (no crash locking) an ARB will give you no problems. A significant amount of breakages were in comp situations, but there have been plenty trail rig breakages too. Just some food for thought.
 
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