Carnage at the dyno... need some advice

[87gnguy]

So today me and my GN buddies have a day at the dyno that a friend of ours has. First two cars get on it and have good runs then it's my turn. I get up there, first pull is 478hp 490ftlbs torque and 0 knock with 22 pounds of boost and 21 degree timing. Ok, so I crank the boost up two pounds and timing up 1 degree. Next run, I run 491 hp and 502 torque still with 0 knock. I'm at about 6400rpm and was just about to let off when I hear a very loud BANG and parts go flying everywhere. So we shut everything down and my first thought was, "oh crap, I just slung a rod" but I notice the motor is still running so I shut it off. We start looking around and the driveshaft is bent and has broken free from the rear yoke (actually snapped the yoke) and the transmission housing is cracked all the way through in 2 places with transmission fluid pouring out. The transmission was a stock rebuild and wasn't that good to begin with. My buddy was watching the car while doing the run and he said the wheels were getting pushed quite a bit to the front of the car. So what we can figure is that since I have stock upper and lower control arms, it put the driveshaft in a bind and broke the yoke at the rearend. Then when the driveshaft was flopping around under the car, the vibration from that caused the damage to the transmission. So upper and lower control arms are coming soon. So, my question is, what transmission should I get that can handle this as well as a driveshaft. And what do you guys think is the best way to spend my money since last fall I put a new stage I motor in it and new rearend with a detroit locker.

Any advice is appreciated and my mods are in my sig.
Thanks,
Casey

 

[Grumpy]

well we run a Dennys 3.5 inch 1350 Series Nitrous Ready Driveshaft .. better yokes an 1350 joints.

 

[turbofabricator]

Casey, Sorry about your bad luck. But I think what happend is the driveshaft moved far enough forward (due to the soft bushings and the chassis being tied down and the wheels running on the front side of the dyno roller. Shoving the driveshaft into the transmission. The other possibility is that you over pressured the transmission and it just broke the trans case and the caused the driveshaft to break. The second scenario I've personally seen on a freinds car. Broke the drive shaft in two pieces. Though the second scenario is a little more difficult to make happen. Takes a rebuilder to shim the pump regulator spring. Some non 200/4R experts think its a turbo 400 and over pressure 'em.
I use "Trans Service" in Lynnwood, Washington to build ALL of our transmissions. He can build a reliable 200/4R to live in a 9.70 car. (425) 774-4966 ask for Dave Sr. He is the nicest guy you'll ever deal with, too. He has ALOT of development time in these trans' He just came up with a new bearing for 'em, too. Requires some machine work to fit. He is continually improving his upgrades. (he hates doing things twice and ALWAYS stands behind his work.)

 

[Boost231]

get a EA stage 2 or 3 and a inland empire 3.5" alum drive shaft with 1350 joints. Good for 1000hp

 

[Boost231]

o ya, got pics?

 

[Major Nutz]

Another vote for dennys 3.5" nitrous ready.

 

[turbofabricator]

I agree with the Dennys shaft, but also try and figure out what happened. At your power level it shouldn't have broke unless it was hurt.

 

[DynamicGN]

Here is a video of the run... I got hit by a piece of driveshaft, and forgot the camera was still on...don't know if we can tell what happened from this.

 

[87gnguy]

I agree with the Dennys shaft, but also try and figure out what happened. At your power level it shouldn't have broke unless it was hurt.

I agree this shouldn't have happened at this power level. Me and the other TR guys were talking and we think his dyno isn't calibrated right. About two weeks ago, our buddy ("Reaper" on the forum) took his car to a dyno in Dothan, AL. There his car ran 441hp and I can remember his torque. He did nothing to the motor and ran 356 on this dyno today. So, we were thinking that my car probably put out somewhere near 550-600 today to do this kind of damage. I think I am going to go with the 1350 driveshaft. Thanks Ken, I'll give Dave Sr. a call Monday
Casey

 

[87gnguy]

get a EA stage 2 or 3 and a inland empire 3.5" alum drive shaft with 1350 joints. Good for 1000hp

Where is the best place to buy this drive shaft?
Thanks,
Casey

 

[87gnguy]

After watching Dan's video, it seems like all this happened after I let off the gas.... I don't remember, it all happened so fast

 

[Boost231]

Call them direct. http://www.iedls.com/

 

[84BuickGNYorkPA]

Glad to hear nobody got hurt, sorry that it let loose though. Looks like it let go after you got out of it, at least you can clearly see the front end lowers right before sh*t hit the fan.
I have the same heads, roller rockers, turbo, injectors, girdled motor but bored .040 over that you have. Never on the dyno, but at 3850lbs and my last trip to the track, Hp calculator puts me at 627 hp to the wheels, so yea I wouldn't be surprised if that dyno is off calibration. http://www.race-cars.net/calculators/et_calculator.html

Chuck

 

[Chuck Leeper]

After watching Dan's video, it seems like all this happened after I let off the gas.... I don't remember, it all happened so fast

My $.02... This driveshaft had fatigue failure from being run repeatedly well over it's critical speed limits...Notice it's bent at about the middle??
The torsionals are "chased" toward the center of a power transmission shaft. If the shaft is not capable of handling that load, it will fail at/close to the center.
GM designed that shaft to handle A LOT less than what you are putting thru it.
From watching the vid:
A: The wheels did not move forward too far on the rollers.
B: The failure did occur on the decel side of the pull. The decel of the engine/trans, and a possible application of the roller brake, could have put enough reverse stress into the shaft to complete the failure.

I buy all my driveshafts from PST, in Tampa. FINE folks to work with, been doing them for MANY yrs, and they ship quickly. They tell me that 90% of stock driveshafts, [especially F bodys], they get to "rebalance for vibration", are bent from exposure to critical speed issues.

http://www.carcraft.com/techarticles/ccrp_0904_drive_shaft_basics_balancing_tips/viewall.html

 

[Pronto]

well we run a Dennys 3.5 inch 1350 Series Nitrous Ready Driveshaft .. better yokes an 1350 joints.

Is that the "pro package" with both front and rear yokes/u-joints or the one with only the front? At what ET do you feel the rear yoke is nessassary?

 

[jasjamz]

Are you sure you didn't tap the brake pedal?

 

[turbo nasty]

Nevermind

 

[87gnguy]

Are you sure you didn't tap the brake pedal?

Yeah, I'm positive I didn't tap the brake pedal. My rear brakes barely work as it is.

 

[87gnguy]

Is that the "pro package" with both front and rear yokes/u-joints or the one with only the front? At what ET do you feel the rear yoke is nessassary?

I'm interested in that as well. I want to buy the complete package ready to go in the car.

 

[87gnguy]

My $.02... This driveshaft had fatigue failure from being run repeatedly well over it's critical speed limits...Notice it's bent at about the middle??
The torsionals are "chased" toward the center of a power transmission shaft. If the shaft is not capable of handling that load, it will fail at/close to the center.
GM designed that shaft to handle A LOT less than what you are putting thru it.
From watching the vid:
A: The wheels did not move forward too far on the rollers.
B: The failure did occur on the decel side of the pull. The decel of the engine/trans, and a possible application of the roller brake, could have put enough reverse stress into the shaft to complete the failure.

I buy all my driveshafts from PST, in Tampa. FINE folks to work with, been doing them for MANY yrs, and they ship quickly. They tell me that 90% of stock driveshafts, [especially F bodys], they get to "rebalance for vibration", are bent from exposure to critical speed issues.

http://www.carcraft.com/techarticles/ccrp_0904_drive_shaft_basics_balancing_tips/viewall.html

I'll buy that theory going by the tiger striping ripples in the shaft. Plus it's bent about 60% back on the shaft right where the ripples stop. A few people even suggested that I touched the brake. I can assure you, the brakes were NOT touched on my end at least. All this happened right as I let off the gas and in less than a second it was over. Then I shut the motor down. The rear wheels kept spinning for about a minute after it was all over and there was no noise or vibration in the rear end so we think that's ok. I'll just need an new yoke and I'll go ahead and put new gears in it.