Half Shafts

EECDOC said:
Guys, I've been running the Level 5 Cobra axles for two months. You need to switch over to a 31 spline diff to make it work though. The MN12 axles assembled length is 5/8" longer than the 03 Cobra axle. This length can be made up in setting the assembled length a little longer on a stock Cobra axle. On the Level 5 axles it's a matter of assembling the inner tri pod like a stock cobra axle instead of the way the Drive Shaft shop does the Cobra setup. I've done a couple sets.

I need to see if the inner 28 spline MN12 tri pod joint will mate to the stock Cobra half shaft. If it does This would be another avenue for a upgrade. If you are rebuilding the rear anyway, swapping to a 31 spline diff is not to expensive, and a set of new 03 Cobra axles is about the same cost as a set of Raxles.

Mike.....

Mike, I'm VERY interested in this as I know that the 31 spline is tougher and will handle more. Since I need a Diff anyways and I'm probably doing the Cobra hub swap as well, this seems to make sense to me to just do the ENTIRE swap. Please PM me with more details. I can kind of visualize what you are talking about, but since I've never set-up a set of half-shafts, I'm not totally sure as to what you are talking about.

-Josh
 
EECDOC said:
Guys, I've been running the Level 5 Cobra axles for two months. You need to switch over to a 31 spline diff to make it work though. The MN12 axles assembled length is 5/8" longer than the 03 Cobra axle. This length can be made up in setting the assembled length a little longer on a stock Cobra axle. On the Level 5 axles it's a matter of assembling the inner tri pod like a stock cobra axle instead of the way the Drive Shaft shop does the Cobra setup. I've done a couple sets.

I need to see if the inner 28 spline MN12 tri pod joint will mate to the stock Cobra half shaft. If it does This would be another avenue for a upgrade. If you are rebuilding the rear anyway, swapping to a 31 spline diff is not to expensive, and a set of new 03 Cobra axles is about the same cost as a set of Raxles.

Mike.....

Mike, this seems like the best economical setup for the HP cars. Can you give more details in what is exactly needed to complete this change over? I for one am interested in a upgrade like this.

Mike
 
EECDOC said:
Guys, I've been running the Level 5 Cobra axles for two months. You need to switch over to a 31 spline diff to make it work though. The MN12 axles assembled length is 5/8" longer than the 03 Cobra axle. This length can be made up in setting the assembled length a little longer on a stock Cobra axle. On the Level 5 axles it's a matter of assembling the inner tri pod like a stock cobra axle instead of the way the Drive Shaft shop does the Cobra setup. I've done a couple sets.

I need to see if the inner 28 spline MN12 tri pod joint will mate to the stock Cobra half shaft. If it does This would be another avenue for a upgrade. If you are rebuilding the rear anyway, swapping to a 31 spline diff is not to expensive, and a set of new 03 Cobra axles is about the same cost as a set of Raxles.

Mike.....

Mike,

Does your new halfshafts still use the 28 spline outer shafts in the hubs ?

David
 
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halfshaft setup

The swap over to 31 spline differential starts with aquiring your choice of trac lok or locker. I'm using a Detroit locker in my car. It is a little harsh for a street car. The Ford truck trac lok or the Auburn pro would be other choices, all of these are offered in 31 spline IRS compatable configuration. These diffs are a bolt in to the 8.8" IRS MN12,FN10,or Cobra housings. Good time to swap ratios too.

The next step is to chose your axle shaft. You will need a set of stock 03 Cobra axles even if you go with the DSS Level 5 shaft. This is because the Level 5's come minus the inner joint. http://www.driveshaftshop.com/MUSTANGC.V..ivnu
The link talks about having some inner cv's but that is old info and they can't supply the inner joint. If you watch the Mustang boards for GP's you can get these axles cheaper than the list price. I got mine through D'agostino Racing out of Florida.

To use the stock cobra axles (31 spline inner, 28 spline like the MN12 outer) It is just a matter of resetting the assembled length of the shaft as outlined in the Thunderbird or 99 Mustang shop manuals. The end to end length of a MN12 axle is 32.565" the end to end length of a Cobra axle is 32.190". The extra length comes from adjusting the plunge of the inner tri pod joint in the inner cv housing. The part number of the cobra axle is 2R3Z-4K138-AA.

To use the DSS Level 5's, it's a little more involved and more expensive as you need 2 sets of axles to make one. The beauty of these axles are the outer stub shafts. They are huge and 33 spline. They come with a custom hub and long ARP race studs. This forces you to convert to the Mustang bolt circle. The hub swap has been talked about many times so I'll not go into that.

The extra axle length is easily made up on these axles by the assembley process. The DSS axles use a external snap ring to retain the inner tri pod off the stock Cobra halfshaft. I did not use this, instead I assembled the inner tri pod just like stock using the internal ring and locking the tri pod all the way out on the shaft. The shop manual for the Thunderbird or 99 Mustang show this assembley.

From there it's a bolt in swap. I also did not use the axle lock nuts supplied by DSS. Instead I used the beefy stock Ford axle nuts that we normally use on the front spindles (the black ones) They torque down nice at 250 ft.lbs.

Any way that's what I'm running now.

Mike.........;)
 
To use the stock cobra axles (31 spline inner, 28 spline like the MN12 outer) It is just a matter of resetting the assembled length of the shaft as outlined in the Thunderbird or 99 Mustang shop manuals. The end to end length of a MN12 axle is 32.565" the end to end length of a Cobra axle is 32.190". The extra length comes from adjusting the plunge of the inner tri pod joint in the inner cv housing. The part number of the cobra axle is 2R3Z-4K138-AA.




Mike,

Thanks for sharing all that info. So all I would need to use the 03/04 cobra halfshafts is 31 spline diff and housing ? Sounds too easy.

David
 
Do I understand it correctly that the Cobra has 28 spline outboard shafts and they are stronger than the SC outboard 28 spline shaft? From what I have read the most common breaking point on the SC is in the outboard shaft regoin. Will this swap help us in that area or only in the other areas?

Mike
 
David, the swap over to 31 spline IRS axles requires changing the ring gear carrier to a unit that has 31 spline IRS compatable side gears.

Mike, I a'm running the DSS Level 5 axles that use a custom 33 spline outer stub shaft and hub. They are much stronger than stock. The stock Cobra axles use a 28 spline outer stub shaft that looks identicle to the MN12. I
know the Cobra guys have had failures at the outer shafts also. So I would not say the stock Cobra axle is stronger at that area. See the two links these are cobra failures, looks real familar!!!!!!!!

http://www.lx.net/jlynch/stub21.jpg

http://www.lx.net/jlynch/stub6.jpg

My point in my original post was that I've been running the Level 5 stuff for a couple months and have drag tested them and they will work in a MN12 car.


Mike.......
 
im looking into replacing my axles, since i think its time, so are the mark viii's just a little better than the stock sc ones? thanks.

ahhh nevermind it was a raxle vs stock sc
 
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Just some clarity

So let me get this straight. I still ne to get my hands on a set of cobra axles for the inner CV. Everything else comes in the Kit? Pricey but I do plan on going over 700HP when alls said and done.
 
Storm_Dragon said:
So let me get this straight. I still ne to get my hands on a set of cobra axles for the inner CV. Everything else comes in the Kit? Pricey but I do plan on going over 700HP when alls said and done.

At least no one can say you dream too small. Not that it's unreachable, just, wow, that's big.
 
CV Drive Axles

Went through the same thing. Got seven cars in various stages of restore and looking for a dependable source for all SC parts, axles no exception.

Forget A-1 Cardone....reground housings....6 months if you're lucky
There's a co. named EMPI that makes 'new' axles [and I use the word new loosely] Tried a set....after 3500 miles they started clunking and it got worse, by 8500 miles they were gone ...and no clutch dumps were inflicted on the axles either

lotta junk out there.....I ended up getting a set at the Driveshaft Shop in North Carolina....so far so good they were 350/pair plus 42 for UPS to LA


acb92sc said:
Im in need of some advice- My CV shaft blew( Grease splattered all over, about 2" of play in inner joint)- I had extras, but the boot is ripped and i dont want to take a chance w/ it. I contacted Raxles, but all they have is the $250 ea/ performance-- more than i need. Are the ones from Autozone, NAPA, etc good enough to support the planned 350HP/450TQ after this winter? If not, does any one have GOOD used ones for sale? Its apart now, and i really want it back together so i can proceed to my motor. Thanx for any help. Adam B
 
Storm_Dragon said:
So let me get this straight. I still ne to get my hands on a set of cobra axles for the inner CV. Everything else comes in the Kit? Pricey but I do plan on going over 700HP when alls said and done.

700 HP from a supercharged 3.8 liter V6????? Good luck with that.

Or are you planning on a different engine and need axles that will handle 700 HP?
 
700hp at the crank? not as unlikely as you think. Yes, it'll take some serious further effort than has been seen thus far, yet who would have figured we'd see these motors where they are now with stock heads?

A new better flowing intake manifold and head could really open a door we have yet to see. XR7 Dave's latest testing with lift and the stock intake manifold sure seems to point to some untapped potential.
 
Mike,
sorry to bring up n old thread like this but just wanted to ask about this. I tore up my stock replacement pumpkin in my car. Broke the halfshaft and it in turn cracked off a chunk off the iron housing, so I need to rebuild it all. The ring and pinion still look to be good so that's gonna get reused. I've had an 03-04 cobra pumpkin in the garage for sometime now my question is can I just swap the gear in it reuse the 31 spline track lock and get a pair of cobra halfshafts rebuild them as you described above and bolt it in? Like David said, it just seems to easy.

Thanks,
Keith
 
I'm working on a set of axles right now attempting to perform this "lengthening" process but not having any luck. I don't see any way to adjust the assembled length as the tri-pod joint is already flush with the end of the Cobra axle. I guess I'm really missing something here.:confused:
 
bummer

This is truly a tragedy :( my rear end has been making offal noises. I have it parked due to this and other reasons. But I have all ready bought the 31 spine Detroit Locker rear end carrier and have the bearings sitting here at work along with the seals. The only thing I am missing is the aluminum housing and CV shafts (located CV shafts. was in process of making a deal!) if I can’t fined a way for this to work I am up the creak and money is moving swiftly down stream.
 
did you see this?

I did see that but it makes no sense to me. How does one "adjust plunge depth?" Slide the boot a 3/4" further down the shaft? If that is all he did I don't see how that is an advisable course of action. The stock wear pattern shows the joint coming to within 1/2" of popping out of the socket. Adding 3/4" to the plunge depth would make it very close to the end of the socket which doesn't seem like a very good thing.

There is no problem using the 31 spline differential and sockets, just making them work with SC axles means you need to be sure that your axles have the smaller inner diameter, that's all.
 
I had just read this on your other posts. Thank you for figuring it out for me :D looks like most of my idea is going to work any way.
 
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