IRS parts and the aftermarket - what's the current state of affairs?

[mikedc]

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DIFFERENTIALS -

There is now an aluminum Ford 9" housing made for IRS. Expensive, but existing. There's a Dana 60 IRS variant too.

Whatever is in the modern Camaro, Corvette, Mustang, and Charger/Challenger will get supported to some extent. But I'm not sure I see a clear winner among them for our long-run aftermarket purposes. Not yet. And some of them smell pretty modern/foreign/metric.

The Ford 8.8" is decent. It seems like a real contender based on sheer availability & support. It's already everywhere in cheap junkyard American IRS vehicles: 1990s T-birds, 2000s Mustang Cobras, 2002+ Explorers, etc. The smaller/import sports car crowd has embraced it.

Any thoughts on which diff will win out and become the Ford 9" of aftermarket IRS's?




WHEEL HUB BEARINGS -

I get the feeling that the aftermarket is settling on the C5/C6 hub as THE unit bearing. (Heck, the whole C5 spindle is the new Mustang-II) The junkyard Ford IRS stuff has a lot of users but the aftermarket doesn't seem to be going for it.

What's the current state of these things? Is there a decent, streetable, rebuildable tapered roller bearing version being made for anything yet? I have seen talk about $700 one-off items but is anything mass produced?


I know you get what you pay for with stock replacement unit bearings. But a supply of good Corvette stock parts doesn't cover everything. It doesn't give us real tapered roller bearings, non-GM bolt patterns, more axle splines, etc. We need some aftermarket here.


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[T_Raven]

I'm building IRS for my Firebird with C5 suspension and a 8.8" diff.

I'm planning to get the SKF hubs. The only aftermarket ones I've seen with replaceable bearings are the GMR hubs, but they were listed only for the front and they are quite a bit more money. They are no longer a sponsor here so Idk what they've been up to lately. Their website is pretty limited.

There are a couple options for a 9" IRS housing and I can't imagine that there would never be one considering the popularity of 9" axles/diffs.

I figure a 30 spline 8.8" out of an Explorer should be strong enough for a pro-touring car. I won't be launching this thing hard on a drag strip, but if I ever wanted something stronger I'd swap it for a 9".

I'm not a huge fan of the D60 so that IRS diff doesn't really appeal to me, but unlike 15 years ago, every V8, RWD car coming from the big 3 has IRS, so I would expect to see stuff like the 5th gen Camaro D60 continuing to be available for a long time.

[mikedc]

I also like the 8.8 IRS diffs for this job.

The F9 is obviously a strong contender. But without an existing OEM IRS usage in the boneyards they cannot really be cheap.

An OEM usage for the F9 will probably never happen again either. The pinion/ring mesh angle (giving it the huge strength potential) also causes a lot of friction. Friction --> gas mileage losses.





I really wonder about the hubs. The C5/C6 is probably the one to bet on.

But it's so frustrating that we cannot get rebuildable tapered rollers inside (and it will probably be some un-streetable $1500 racing version if we do).

A pair of modern unit bearings is basically a timebomb. The explosion only costs $500 but that is still what it is. You never know when you will be forced to pull over & pay up again.

[T_Raven]

To me the biggest downside of regular style C5 hubs is the potential for brake pad knock back with fixed calipers. Rebuild-able hubs with bearings that could be packed and adjusted would be nice, but so far from what I've found online, people have had much better results with the SKF hubs

[mikedc]

Wait, shouldn't the brake knock-back be less of a problem on a C5 hub rather than more? It's a pre-sealed item.

[T_Raven]

Wait, shouldn't the brake knock-back be less of a problem on a C5 hub rather than more? It's a pre-sealed item.

The problem is any slack in the bearings can't be adjusted like you could with a spindle and nut. I don't know how much of a problem it is on a street car with good hubs, but I've read guys have upgraded to the SKF hubs to minimize the knock back on track cars.

[mikedc]

That makes sense. Sealed bearings eliminate the possibility of huge slop, but they leave you with a small amount that cannot be gotten rid of.

I guess that ends up being an argument in favor of floating calipers.

[T_Raven]

That makes sense. Sealed bearings eliminate the possibility of huge slop, but they leave you with a small amount that cannot be gotten rid of.

I guess that ends up being an argument in favor of floating calipers.

Yeah, floating would be good. I want Baer 6p calipers. They provide their verislide set up for c-clip axle cars. Idk if they could provide those for C5 calipers or not. I figured I'd call and ask when I get to that point.

[David Pozzi]

There are two beef-up center sections for 5th gen Camaros. Hammerhead; https://driveshaftshop.com/blog/?p=853 which has 12 bolt internals, and the Strange, which has Dana 60 internals. http://www.strangeengineering.net/high-performance-street/complete-rear-end-assemblies/s60/independent-s60-camaro-complete-rear-end-assembly.html The Dana is super-strong with a 9 3/4" diameter. The limitations are that gear ratios available start at 3:55 and lower.

The SKF hubs are great, we have run them a lot and seen no play yet. James Shipka has run several One Lap Of America's on them pluse many many events, all on the same SKF hubs. Here's a video on them. They are calling them X Tracker hubs now. https://www.youtube.com/watch?v=T2d8_G0zwAQ

[David Pozzi]

That makes sense. Sealed bearings eliminate the possibility of huge slop, but they leave you with a small amount that cannot be gotten rid of.

I guess that ends up being an argument in favor of floating calipers.

I'm an old-school guy who used to prefer a traditional spindle and tapered bearing assembly where you can adjust them, lube them, and replace them. But the more I've learned about the Corvette Unit-Bearings, they are a better answer to our needs.

Tapered roller bearings require .001" clearance, so you always have some play. The larger the rotor, the more deflection and brake pad knock back you have. The traditional spindle that comes on a stock Camaro for example, is too small and lacks stiffness, the spindle itself will deflect. The bearings are a slip fit on the spindle so there is more lash or give there. The whole assembly lacks stiffness for the loads we are applying & bearing capacity is near the limits, although we have run stock tapered bearings a lot with no failures. Upsizing to NASCAR sized spindles and bearings is the only way to increase stiffness on this type system to what it should be.

The 3rd generation SKF unit-bearings for Corvette have enlarged outer ball bearings and can run preloaded, they last over 500% longer than the previous versions. If one of these develops lash, it's time to replace it. If you could adjust it, the preload could be re-set but the bearing is worn to the point where it will be failing soon anyway.

[T_Raven]

There are two beef-up center sections for 5th gen Camaros. Hammerhead; https://driveshaftshop.com/blog/?p=853 which has 12 bolt internals, and the Strange, which has Dana 60 internals. http://www.strangeengineering.net/high-performance-street/complete-rear-end-assemblies/s60/independent-s60-camaro-complete-rear-end-assembly.html The Dana is super-strong with a 9 3/4" diameter. The limitations are that gear ratios available start at 3:55 and lower.

The SKF hubs are great, we have run them a lot and seen no play yet. James Shipka has run several One Lap Of America's on them pluse many many events, all on the same SKF hubs. Here's a video on them. They are calling them X Tracker hubs now. https://www.youtube.com/watch?v=T2d8_G0zwAQ

I hadn't seen the Hammerhead diff yet. That's cool there's another option out there. I don't have much desire to own a 5th or 6th gen Camaro but maybe the 7th or 8th will tickle my fancy lol.
8.8" diffs are pretty comparable to a 12 bolt though, so for what I plan to do they are cheap and strong enough.

That's good to know people are having good results with the SKF hubs. I hadn't thought about the little bit of clearance you need in tapered roller bearings.

[a67]

The tapered roller bearing clearance is required as it is set cold. As the bearings heat up they expand and take up that clearance. And are now 'loaded.' There are solid sleeves available that use shims to set the end play. IIRC, Tobin has/makes them.

But this doesn't fix the lack of stiffness in the rest of the assembly.

As for an IRS, it is good that there are many more choices. Way back when I was younger there were two main choices: a Jag or a Corvette rear. With the Jag being more popular mainly due to the inboard brakes.

Bob.

[David Pozzi]

We had enough deflection on a stock second gen spindle (14" rotor) to see the rotor contact the sides of the caliper bridge area. I don't recall how much clearance the rotor had static, maybe .150".

On the rear, take a 3' long 2x4, jack the car up and pry against the wheel and see how much it deflects. It's a lot!

[Twentyover]

The tapered roller bearing clearance is required as it is set cold. As the bearings heat up they expand and take up that clearance. And are now 'loaded.' There are solid sleeves available that use shims to set the end play. IIRC, Tobin has/makes them.

..

Bob.

This is actually the stock deal in an MG front wheel hub. There is a solid spacer that picks up the innner bearing inner race, and the outer bearing inner race. You shim to like .003 clearance, then tighten the wheel bearing nut to like 80 ft-lb. Since the stack is now solid- inner bearing inner race, spacer, shim stack, outer bearing inner race, tab washer, and spindle nut, you could tighten the spindle nut till the cows come home, you're no loading the bearing rollers any more.

This ends up being slightly more fatigue resistant than the typical front wheel bearing tightening technique, and keeps you from playing the 'tightn wheel bearing to 12 ft/lb, back off one flat, throw the chicken bones in the air and sacrifice a pig to the vodoo gods' technique that common in the US.