Got the SHAFT!!!!!!!!!

[69MyWay]

Man...

Took my 69 Camaro to www.speedinc.com today to do the first live dyno tune since I put the car together. It has been running on a mail order tune since 2005. At that...it ripped a 12.5 at the quarter at 111 on C5 Goodyear runflats. It has carried me 11K trouble free happy miles...and been to the 1/8th mile many times. I am not shy about the throttle either when I'm out of traffic.

With all that said...I found out two things. First...all this time I have only had 85% of my throttle. I wondered why the car laid down a little at the top of the quarter...now I know why.

SECOND - MY DRIVE SHAFT SNAPPED at 6,300 RPM and destroyed the exhaust, some tunnel wiring, and the floor pan.

We rescheduled to finish it up on 5/14 - but I have to obviously fix it by then. I'm also a bit concerned about making the mid west challenge if I don't pull it together.

Funny thing is, I'm not mad about it. I'm glad it happened there...and not anywhere else. I almost drove the car the 150 mile one way trip to the dyno, but opted out as a buddy was giving me some mufflers for my wife's car that wouldn't have fit in the camaro.

Sorry for the long post. Now I have to try to make some lemonade out of the lemons.

Oh...before it broke it put down 362 hp at the rear wheels at the moment of breakage.

[n2protour]

was that the original driveshaft or aftermarket one that came as a kit with the tranny? I had the u-joints broke on me long time ago when I did a burnout. Luckily the emergency cable kept the driveshaft from touching the ground.

[69MyWay]

Stock shaft that had been balanced and set to bolt to the 9" axle.

There is no evidence of rust or other damage to it. The trans mount is secure...and there is simply no other explanation.

The dyno guy said that sometimes when there is a little bend or unbalance situation in the shaft they will do this.

The drive line angle is good and I can't imagine the dyno put more stress on it than normal street driving.

[GregWeld]

Could be that depending on the rear gears and tranny combo -- your old stock shaft hit whats known as it's CRITICAL SPEED.

Do a little research on the subject. I think David Pozzi has some info on it on his website (can't remember). But my guess is that is the cause of the failure.

[Rick D]

Originally Posted by 69MyWay

The dyno guy said that sometimes when there is a little bend or unbalance situation in the shaft they will do this..

And Jim (the dyno guy) has a VERY heavy right foot, and some cool and fast cars!!

[thedude327]

362 to the rear wheels is about 452 at the crank. Nice motor. Are you going with an aluminum driveshaft to replace your 2 piece?

Paul

[1969x11]

If you dont mind me asking what are your engine specs, t-56? I'm running a cam only LS1 in my 69 and your got me wondering. Thanks

[buickfunnycar.com]

Holy crap,sorry to hear that...amazing how it tore @ only 6300.

[69MyWay]

The critical speed thing makes sense to me. The main part of the shaft after all is 40 years old - so between age and the magic frequency it let go.

I will tell you the engine sounded so sweet just before it came undone.

Engine specs:

stock short block - rebuilt with a ring/bearing kit. I bought it for $400 in 2005 as a take out from a stolen 2000 Trans Am that had hit the road bed and broke the pan open. It was starting to spin a rod bearing. I put a $160 crank kit in it and was good to go.

I bought a "stage III" SLP head/cam and 36# injector kit. It is a LS6 intake (non ported) and stock throttle body.

I put a set of non-emission Pace Setter headers on it and had to make some small changes to get them around the rack on the drive side - passenger side slipped right in.

Trans is a 4L60E out of a truck with a stock rebuild on the clutch/seals and a trans go shift kit. It is a TCI 2,800 stall converter with lock up.

All that is tied to a Ford 9" with a 3.5 gear.

For what it is...the whole combo was a major budget build. Nervous system is a Painless Harness on a 98 Camaro PCM.

I made some calls this afternoon. Hope to have a PSTD shaft soon and will most likely get a set of PYPES mandrel bent 2.5" exhaust and Race Pro mufflers.

The big issue is the floor. I'll post pics later when I can get them off the camera.

Here is what the bottom use to look like...and the motor. No bling under the hood.

[732ndgen]

same thing hapend to a friend of mine with a 70 charger.took out exhaust,transmision,bellhousing,driveshaft and the part of the u joint hit the dyno operator in the chest.