Long story short...my passenger side half shaft sheared apart at the weld last Friday night on a hard launch at the track. Dana 44, carbon fiber half shafts (well...one of them now), complete rear-caps and bolts-stub axles all cryogenically processed, longer bump stops, all poly bushings, c beam plates, stiffer rear spring (code NYR, OR NYU,, I forget).

I know this has been talked about before, but what does everyone suggest? Get the Denny's nitrous ready shafts, and risk finding the next weak link? Go with one of the solid axle conversions, and sell the 44 to recover some of the expense? Put the stock ones in, sell the car, and buy Bowtie8's twin turbo 91? 😏. I'm just worried that if I go with Dennys, I might blow the rear apart, then I won't get anything for it.
Help me decide...

 

Well you're just having to much fun launching that little monster.

Only you know if you plan to circuit track race or just drag race. But if just drag race and street driving your wasting your efforts and resources driving an IR. The old 44 will bring over $500 towards a straight axle. And you can still circuit race a straight axle car but just not as competitive.

IMHO I think the split shaft speaks for itself you need better for a rear end. BTW can you get a refund on the half shafts?

I think selling the car to buy another is pretty much starting over - unless that's exactly what you want.

 

Good point. I just don't really have the cash right now for the solid axle conversion. Maybe I'll just put the stock ones in, save up, and avoid the track. As far as starting over, his car is faster, and already has a Ford 9" rear. Hmmm....

 

Hi
I twisted my half shafts like licorice, with an auto trans car.
I supplied one to a drive shaft place and got some steel ones made to size and replaced the aluminum ones.

Never a problem with half shafts since.

Now if only I could get a reliable auto transmission ....

 

More than reliable.

 

 

My car came with steel half shafts and driveshaft. There must be more out there.

 

I've been running Denny's steel shafts for a long time now. After putting them in I broke another spindle. I had Billet spindles made by summers brothers, and put in a Eaton Tru-Trac. I still go thru u-joints turning the needles to dust, and twist the tru-trac heilicoil gears but at least nothing totally breaks off anymore.

 

In my 1992 I went the opposite of most people. I put a 9" solid axle in first and still have a stock engine. I took it out twice this year with piece of mind. I do worry about breaking the clutch and transmission (ZF-6 Speed)

Look up Will's threads he went very fast with the IRS.

Steve

 

Why? There are almost never any threads about ZF failures. Anyone can break anything, I guess...but that is a tough trans.

 

If you weren't breaking parts, you'd be looking for more power! Gotta go faster!! Just be glad you're not racing P-51 Mustangs!

USS Enterprise aircraft carrier: 280,000+ shaft hp, and we bent a 4 ft. dia. propeller shaft!

 

True-But I dump the clutch at 4600 RPM (on rev limiter) and power-shift each gear change. The hit (to me) is hard. Over the years I have about 25 passes on the transmission. No regrets on the solid axle install.

Happy Thanksgiving
Steve

 

Yep, that is a "hit" for sure.

TPI421Vette is doing a simliar technique w/about 700 hp. I think he's got 100's of passes on his ZF.

 

Like steel D.S. sometimes with weight comes strength start doubling or more the power output somethings gonna go.

 

One thing I just thought about... I'm guessing these solid axle conversions don't have any provisions for wheel speed sensors and rings, meaning I would lose ABS/ASR?

 

Post like these just worry the crap out of me. I like to go up to the track on test and tune wensday nights and run. Been looking for a better launch but these post offer the other side of the coin to doing that. Whats a guy to do as I really like running the quarter. Best has only been 14.03 @ just under a 100mph. I gotta hit 13s at over 100 to be really happy with it. lol, same sickness as many in here and I don't want to be cured. BTW Ron, great pic and welcome home..

 

Set up and technique (be in tune with your machine) and then go have fun at the track! What are your 60' times? 2.0x? 2.1x? The launch is really where you're testing your parts as your putting the highest torque down at that moment. People like Rklessdriver are 60'ing 1.3 seconds and faster on stock axle shafts...that shows what CAN be done. Everyone else braking stuff at a lower level than that is only showing that they're doing something wrong.

Set up: Getting the car set up properly is one thing. OR, avoiding a poor set up, is critical. One example of a set up that could cause issues might be a very aggressive, multi disk clutch. That is going to "hit" the drive train very hard if not manually and carefully modulated by the driver. That will break parts, while not necessarily producing the best performance.

Technique: Whatever you have to do w/your car to get a smooth transfer of power from when you're staged to fully launched with help. That takes practice and paying close attention to the car and how it behaves/responds during the launch procedure. But "side stepping" the clutch pedal is one way to break things, while also probably not producing the best launch results.

I'd say that at the level you are at and shooting for, nothing should be breaking. If something is breaking at the 13 and 14 second levels, one would need to seriously re-assess how they're operating their car.

.

 

At least from my experience, you probably don't have to worry for a while. That's not to say nothing will break, but I was hitting 125-127 in the quarter that night, with sticky Nitto nt555r extreme drag radials. I found the weak link 😁

 

Those carbon shafts were not the best for your application in the first place IMO. Carbon makes great drive shafts because it only has to deal with torsional load but the half shafts in a C4 Corvette also has to deal with the lateral loads of controlling the wheels camber. I don't think that the way these carbon tubes are wound and then bonded to the end yokes is very good at handling both torsional and lateral loading.

I got away with running stock aluminum shafts for many years. A lot of my success with the stock IRS was in the setup which I have covered countless times here. As my car got faster and faster, I had to do other stuff to manage power as well but I ran down into the high 8 second (1/4 mile) range before I needed to worry about managing power. Weakest link IME are the u joints. My car would crush the needles in about 50 passes... sometimes I could get 75 passes out of them. I broke a bunch of u joints before I figured out how to catch them before they broke. I also busted an outer stub axel running it longer than I knew I should have . Eventually I worked up a maintenance schedule of inspecting u joints every race, replacing them when they were pushing grease from the seals and replacing outer stubs and half shafts every season or 100 passes. Tremendous amount of work, keeping the IRS racing at that level.

I converted to a 9" sold axel 2yrs ago and it's the best thing I could have done. It's not the solution for everybody thou. It costs a lot of money. And it's not indestructible like some think... 2yrs and I already have to replace the ring and pinion in my 9".

The member here that bought my IRS has a pretty fast C4 and it was unbreakable for a long time under his car... once he started having problems there were a lot of them in a row. All stuff I typically replaced before failure. He's had more failure from u joints and half shafts than I did... but I ran the dog crap out of that IRS before he got it, so some of it was due to break and he street drives his car way more than I did mine which is hard to account for. He recently pretzeled a half shaft right after putting new joints, half shafts and stub axles in it.... I think that shaft that failed had a flaw that caused it but who really knows. He has a set of shafts coming from Enland Empire with thicker tubes and billet yokes. In the meantime he put an old stock shaft in there to get by and it's kicking *** again.... I talk with him every week about the car and we are constantly working on how to keep things together and make the IRS better within his budget.

I don't really know what more advice to offer you other than if you are racing these cars you need to be looking at the shafts, bearings and joints. If you still have the Posi you need to be checking the breakaway TQ. Do this stuff before every race and after every race. Replace stuff you think is suspect. Eventually you'll get the hang of figuring out how long stuff last under your car.
Will

 

Thanks Will.
Why do you have to replace the ring and pinion already? Do you race at Mason Dixon? If so, I think I have seen you run. Who did your rear? Was it one of the available bolts in kits, or a custom install? I always expected the carbon fiber to snap or the u joints to break, but I was surprised to see the weld on the end of the aluminum tube section actually sheared off.