Strongest IRS Differential

[JustinOlson]

I'm building a tube chassis Datsun 280z with a 2JZ and a Gforce Dog Box. It will have C5 vette hubs/uprights. I currently have a Nissan R230 differential (9.06" ring gear), but people have had issues breaking input and output shafts on these.

 

http://www.supraforums.com/forum/showthread.php?t=566104

 

With the dog box and drag radials I'm worried I will break the rear diff. I don't want to buy custom axles for the R230 to the C5 hubs if I'm just going to be breaking the diff all the time.

 

What would you guys recommend for a very strong IRS rear diff?

 

-J

[kiwi303]

Holden GM IRS in the HSV does a good job holding up to hurling a lardy tub of a 4 door full size sedan around with 300KW under the bonnet.

 

There are HP adder kits fitting turbos to Holden HSVs and Commodores for 750+Hp with no mention ever made of upgrading the diff.

 

Someone on here has been fitting one to their aussie Z, and has a write up, being a GM unit, they must be found in other GMs stateside, such as the Monaro/Ponty GTO, and the G8.

[JMortensen]

The GM diff is a 7.75". While I don't know of failures, I'd be surprised if it was as tough as an R230. You can do a custom Ford 9" for IRS. Not cheap, but can be done. The 8.8" is also pretty tough, comes stock in the few years of IRS Mustangs and quite a few Explorers.

 

http://www.kitcarmag.com/howto/rcc_specialty_products_ford_9inch_irs_cobra_replica/index.html

[JustinOlson]

Jon,

 

Do you know anything about the Viper IRS diff? Are they Dana 44's? These seem to be pretty strong as Sal's TTViper has gone 7.5's with it on radials. He does run a spool in his diff.

 

[BRAAP]

Not to put too fine a point on the subject, but if you have enough power, enough destructive desire, and the ability to abuse FAR beyond what is required to be truly fast/quick in any Z, then NO diff will hold up and you'll bust it every time.

 

Now take a smaller, known weaker differential, (the R-200), more than enough power and traction that drags the rear valence on the asphalt, possibly enough to quite literally flip the car over backwards, and try as hard as you can to go as quick AND as fast as possible without busting the diff, you’ll be rewarded with a fast car as pictured below. Add a beefier diff such as the R-230 and chances are you will have more fudge room under more extreme conditions, (i.e. drive more abusively without failure), but honestly, if you truly need more differential strength than what is depicted below, you are only being abusive for the sake of showing the world your ability to bust parts because you can, not because you want to be fast.

 

For what its worth, this V-8 topped with a Blower and dual quads is also running N2O, R-200 differential, and the drivers admit to not being ginger on their launches!

 

 

 

Anyone who thinks they “need” more than an R-230 in an S-30 chassis to go faster, either doesn’t know how to drive or deserves the empty wallet to replace busted parts!

 

Of course, that is just my opinion.

Edited January 9, 2010 by BRAAP

[MAG58]

Perhaps the bigger question is, if you're going to go through all the work to build a chassis drag car, why not just put a solid rear axle in it?

[JustinOlson]

There is a big difference between a power glide on slicks compared to a manual on radials. Shock loading is FAR different between the two. I was just looking and thinking about a better option before I dive too far into this build.

 

At this point I'm leaning towards using M&H slicks instead of the MT Radials. This should save me a lot in terms of tire shake and broken parts. Besides that, I'm going to look at converting my triple plate clutch into a dual disc unit with more slip-able discs.

 

Ford 9" IRS diffs are interesting me right now:

 

http://www.dutchmanaxles.com/1_irs_centers.html

 

http://www.currieenterprises.com/CEStore/categoriesre.aspx?id=943

 

http://www.off-roadweb.com/tech/0810or_ford_9_inch_axle_nine_inch_nailed_part_i/photo_16.html

 

http://www.cwiinc.com/9inchsuspension.htm

[Scottie-GNZ]

Z-Gad launches with 20psi and 100-shot @ 5000RPMs and his Techno-Toy/R230 setup seems to holding up fine.

[Boy from Oz]

I understand there is no known application of the GM IRS diff in the US other than the Pontiac GTOs and G8s, so this is probably of little help. I have just measured the output shaft from a GM diff in my LS1/240Z at 30mm. Rather than speculating of the capability of a diff you might want to consider its design as part of your assessment. I acknowledge there are other factors but judging by the photo in the first post the shaft dia is critical.

[sweetride2go]

Ya, lucky for Oz they have plenty available to them down there, but so far as I've found the GM IRS units are hard to come by. Maybe Grumpy could chime in but he was showing the 'vette IRS units and differences in a tread here somewhere.

 

You might give these guys a call http://www.cwiinc.com/index.html they sell IRS units with the option of a Dana 44, Ford 9", or even a quickchange centers. Maybe they would sell just the center section. And they are somewhat local, being in Castle Rock, Wa.

 

Cheers

Ryan~

[BRAAP]

Are you building a dedicated strip car, running in the 8's 7's? As MAG58 mentioned solid axle seems like the easiest most logical route especially with solid axles ability to get he tires to bite in a way IRS just can't do.

I do admit, it would be cool to see just how far IRS can be pushed even if for no other reason than just the sake of doing it.

[letitsnow]

Why not get a set of output shafts made from 4340(M)?

[JMortensen]

Do you know anything about the Viper IRS diff? Are they Dana 44's? These seem to be pretty strong as Sal's TTViper has gone 7.5's with it on radials. He does run a spool in his diff.

Vipers do use Dana 44s, as did some older Vettes for just a couple years in the early 80s. Dana 44 is an 8.5" ring gear.

 

I have just measured the output shaft from a GM diff in my LS1/240Z at 30mm. Rather than speculating of the capability of a diff you might want to consider its design as part of your assessment. I acknowledge there are other factors but judging by the photo in the first post the shaft dia is critical.

I'm guessing that comment is directed at me. There is more to a diff than the output shafts, and after selling quite a few gearsets because the pinion or ring teeth sheared off, I can tell you that ring gear diameter is important too. Drag racers get to a point pretty quickly IME where the weak point is the ring and pinion size. It's speculation, but more than just idle speculation.

[JustinOlson]

Its not that you can't go very quick and fast on a R230. This has been proven by the BL 2JZ powered S14. It has been 8.1 @ 171:

 

http://s79.photobucket.com/albums/j158/ainoble/IFO%20Baytown/?action=view&current=Duys240.flv

 

This car utilizes a Power Glide and a R230. They can definitely take a lot of power. I was just curious if there is anything reasonably priced that I would rather use then the R230.

 

This is not a dedicated drag car. It will make ~1150whp when all is done. That will be through a clutch, so I'm going to have to ramp in boost off the line. Shifts will be interesting to say the least with Clutchless full throttle shifts.

 

When not in "drag trim", it will be sporting 16" slicks for road racing. I will also run around with street tires and a 66mm turbo for having fun.

[Boy from Oz]

...I'm guessing that comment is directed at me...

 

You guessed wrong! Read what I wrote.

[turboHLS30]

If your worried about breaking the diff then run slicks. Slicks won't instantly stick like radials so it won't be as hard on the diff as the DR's.

[jnjdragracing]

Not to put too fine a point on the subject, but if you have enough power, enough destructive desire, and the ability to abuse FAR beyond what is required to be truly fast/quick in any Z, then NO diff will hold up and you'll bust it every time.

 

Now take a smaller, known weaker differential, (the R-200), more than enough power and traction that drags the rear valence on the asphalt, possibly enough to quite literally flip the car over backwards, and try as hard as you can to go as quick AND as fast as possible without busting the diff, you’ll be rewarded with a fast car as pictured below. Add a beefier diff such as the R-230 and chances are you will have more fudge room under more extreme conditions, (i.e. drive more abusively without failure), but honestly, if you truly need more differential strength than what is depicted below, you are only being abusive for the sake of showing the world your ability to bust parts because you can, not because you want to be fast.

 

For what its worth, this V-8 topped with a Blower and dual quads is also running N2O, R-200 differential, and the drivers admit to not being ginger on their launches!

 

 

 

Anyone who thinks they “need†more than an R-230 in an S-30 chassis to go faster, either doesn’t know how to drive or deserves the empty wallet to replace busted parts!

 

Of course, that is just my opinion.

I love our R200 and it is still going strong and more HP coming soon.Jerry

[bob1]

This may be stupid, but has anybody broke a good ford .8.8?? They're everywhere, cheap, and I suspect with the right parts combo, fairly strong.

If it's not obvious, 2002 up exploders are IRS, and use an 8.8. They're 71" wide fender to fender, z31's are 67". Seems like some negative wheels like corvette would fit under z31.(Yes, you can drill a corvette pattern on a Ford flange.)

 

Oh, bye the way, thanks for the link to dutchman 9", they're stumbling distance from me...

[lazycat5]

I ran several 11. and 10. second mustangs in the past with 31 spline axeled 8.8's without breaking them. Two of my best freinds have run mustangs in the very low 9's with fully built 8.8's for years with out problems. The 28 spline 8.8 rear can break!; with no more than a change to sticky tires.

[sweetride2go]

While the R200/230 hold up well, an advantage to going with a Ford/Chevy center would be a large range of gear ratios to choose from.

 

Cheers