Thread: Which is better?

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Most everything I've built in the last 10 years got a 9" Ford rear end in it. I want something a bit different for the '57, thinking I'm going to go with an IRS.... I don't want to spend the huge bucks for a 9" IRS (unless someone would know of a used one for a decent price) and am leaning towards either a 'Vette IRS or an 8.8" Ford IRS. (like in the Cobras).

My last fast Vette was a '73 big block 4 speed car, could break a half shaft almost at will with that. Wondering if some of you have some real world experience with either IRS I mentioned and how they would live with rear wheel horsepower in the 600 range? I'm sure the Vette's have improved since '73, but I have very little experience with them. This won't be a drag car with slicks, but I don't want to have to baby the thing every time I launch it, either!

Thanks

Dave, I believe I have seen these guys at many Good Guys shows. Pretty impressive work, that seems performs really well, at least the video they have, the car does. They have been doing Tri5's with Corvette C-4 suspension all the way around for a while now. If I were going to build a Tri5 I would be sourcing C-4 suspension. Good luck deciding. Here is the link for reference, something might catch your eye about installation.
55-57 Chevy with C-4 Corvette suspension

Yeah, seen there stuff.... mine will have nothing resembling the stock frame, not sure a C-4 suspension is appreciably stronger then the previous stuff, is it? C-4 Vettes were done in 96(?), it was after that the factory started putting out a car with any horsepower.......

When you say "...like in the Cobras" that's the Mustang Cobra, right? I think the '99's were only 28 spline and had problems. '00's and later were 31, and then you see a lot about '03/04 being "stronger" but I'm pretty sure that's just carbon clutches for better load sharing. Since we're talking the '57 tucking in a Ford IRS should be the right answer anyway, just for the fun of talking about it.

Yeah, the Mustang Cobras. One of Andy's customer's put a Kenne-Bell supercharger on his Cobra (I think an '07 or '08) a year or so back and it's still living! Think we'll be up at Andy's with the new drag car next week, going to check with him on it, too. SVT still lists some of the go fast pieces for the unit, too. But, the LS7 Vettes seem to be getting along ok with the new style trans in the back set up, too.

But yeah, the Evil Twin that lurks within sez the Ford would be the way to go!!!!! Got the front suspension pretty much thought out what I want there.....Mustang struts are strong, handle great, and are reasonable at the junkyard! AFCO has a coilover conversion for them, so handling could be much "enhanced"!!!!

One of the shops here had a Z06 'vette that was cranking out some massive rear wheel HP a couple of years ago - the customer simply gave the order that he wanted to beat his brother's best time in the 10's. They had to beef up the tranny to take the power, but as I recall the rear end was OK. That thing was wicked!!

Don't know the expense but I have read about Vett. IRS with 9" Ford center section..

Originally Posted by cffisher

Don't know the expense but I have read about Vett. IRS with 9" Ford center section..

Kind of hi dollar. Not all it's cracked up to be, either. Still have the Vette half shafts and joints. By the time you replace all that with moly half shafts, billet yokes, and 1350 joints it all gets just strong enough to wipe out the bearings in the uprights! Think to get any life expectancy out of an IRS it has to be the newer Vette, 8.8". Both are designed to live behind 500+ horse engines and you know like any other part the OEM's have to warranty they have a bit of extra strength built into the unit over and above what the engine puts out....... Well, I know Ford engineers do it that way anyhow...

Originally Posted by rspears

One of the shops here had a Z06 'vette that was cranking out some massive rear wheel HP a couple of years ago - the customer simply gave the order that he wanted to beat his brother's best time in the 10's. They had to beef up the tranny to take the power, but as I recall the rear end was OK. That thing was wicked!!

That would be the new style with the trans in the back, right???? (Gotta remember, I ain't no chebby guy!!!!!)

Originally Posted by Dave Severson

That would be the new style with the trans in the back, right???? (Gotta remember, I ain't no chebby guy!!!!!)

Yeah, a trans-axle unit. From Wiki -

The Z06 utilizes the specially built M12 6-speed manual transmission. While outwardly similar to the base-model MM6 manual transmission, the M12 transmission is unique to the Z06, and not available on other Corvettes, i.e., coupés and convertibles. The M12 has more aggressive gearing to increase torque multiplication in most forward gears, allowing for more rapid acceleration and more usable torque at higher speeds. A transmission temperature sensor was added to protect the M12 from higher thermal stresses. The sensor warns the driver, via the Driver Information Center, with a "TRANS OVER TEMP" message if transmission temperatures approach their operating limits, and which could lead to damage if the transmission were not allowed to cool down. As with all C5 Corvettes, the transmission is located toward the rear of the vehicle, as a rear-mounted transaxle assembly. This allows a better overall weight distribution for the vehicle, as the weight of the transmission offsets some of the weight of the forward-sitting engine.

I've sent a message to one of the young guns that ran the shop to see if they did anything to help the rear end survive, and asking what RWHP they were seeing. He may not get back to me for a while as he follows his own internal drummer on things others ask about....

Dave---the C4 vets used dana 36 in the at and Dana 44 in the sticks-------the dana 44 has been used in most things in recent years(since the f9 went away in 86 or so?) I don't remember if this is supposed to be a road car or a drag only?


The new Camaro rear suspensions are doing pretty good in the NICKEY cars with rwhp around 800----different drive shafts and half shafts--these rears have a much better opportunity to do different shcks/springs than the vets with that cross leaf spring-------also brakes---------you can prpbably source a Camaro rear assy for less than the brakes would cost-if you want I'll quis Corey about what they are doing to them-------

Yeah, they're all starting to show up in the yards! Must be Vettes and 'Maro's sold to guys who run out of talent about half way through 3rd gear. The old Dana 36's were a spindly piece that would break if you looked at them cross eyed, 44's weren't much better! I'd almost completely forgotten about the 'Maro IRS setups, probably not as plentiful yet but they'll be around, too. Yeah, if you could, ask Corey how they're holding up and what the tricks are to making them live!

The '57 will be street (by my definition) and some Texas Mile type stuff. Things go right with the car and an old dumb Norwegian improving the aero, maybe even B-Ville. Seems like all the rest of the old farts congregate there to go fast once a year, might as well join them!!!!

Thanks for all the help and input gang, keep it coming!!!!

8.8" Ford IRS would probably be the easiest to locate since some Thunderbirds and Lincolns also used an 8.8" IRS, but those will be 28 spline units, and I'm not sure how much HP you are planning. a 31 spline 8.8" out of an Explorer is plenty strong, but that's not IRS and not what you need.

How about a Viper unit Dave?

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Originally Posted by Matt167

8.8" Ford IRS would probably be the easiest to locate since some Thunderbirds and Lincolns also used an 8.8" IRS, but those will be 28 spline units, and I'm not sure how much HP you are planning. a 31 spline 8.8" out of an Explorer is plenty strong, but that's not IRS and not what you need.

I think the Explorer went to IRS in '02 thru current and should have 31 spline axles.