Broken trans case on the dyno today...***PICS***

[yullose]

Among other things...
My buddy and I took our Buicks down to the chassis dyno today to make a few pulls... He got on first, and broke the car on the first pull...

I was running the dyno and was standing at the front door when it came apart at 130mph. I got hit in the feet with U-joint caps...

Not sure what broke first, but the case is cracked, the driveshaft is in several pieces, the exhaust is junk, and the floor is mangled up pretty good.
He did manage to see 440hp before it let loose though. He was happy about that.

After seeing the carnage, I decided not to put my car on the machine. I just took the car home and returned with my Dually and trailer....

 

[SS/GN]

Possible cause and effect.

First sorry to see your bad luck,Inoticed your post on another sight and although i usually never post I thought this might help.I am a mechanic by trade and have been working on race cars for years,Ibelieve your problem is an internal tranny part broke causing the tranny to lock up and try to stop the tied dpwn wheels at 130 .Be thankful only the driveshaft broke you only broke the weakest link if you would have had a bulletproof driveshaft you may have done even more damage.Please tale the diff cover off and check posi cluthes as well as all hardware including motormounts.That car took an awful beating.Best of luck

 

[chris718]

based on what ive seen in my career fractures in that area are related to driveline vibrations usually due to drive shaft failure.

 

[yullose]

First sorry to see your bad luck,Inoticed your post on another sight and although i usually never post I thought this might help.I am a mechanic by trade and have been working on race cars for years,Ibelieve your problem is an internal tranny part broke causing the tranny to lock up and try to stop the tied dpwn wheels at 130 .Be thankful only the driveshaft broke you only broke the weakest link if you would have had a bulletproof driveshaft you may have done even more damage.Please tale the diff cover off and check posi cluthes as well as all hardware including motormounts.That car took an awful beating.Best of luck

Yeah... Glad it wasn't my car...

When I first looked at it, I came to the same conclusion. The motor was chugging and really grunting hard when it broke... I too believe something broke inside the trans, locked it up, and twisted off the driveshaft because the car was strapped down to a 2000lb roller spinning at 130mph.
This seems to make the most sense to me...

 

[yullose]

based on what ive seen in my career fractures in that area are related to driveline vibrations usually due to drive shaft failure.

I guess if it would have locked up, then there would be alot more broken pieces...

We had a helluva time getting the wheels slowed down fast enough... It sounded like the whole car was being torn apart underneath...
I guess that's what busted the trans...

 

[jakeshoe]

I'm with Chris...

When a driveline breaks, it sends a treemendous shockwave through the car.

I've seen drivelines let go causing failed trans case or tailhousing, harmonic balancer, converter, alternator brackets, input ring gear on Th350's, and rear diff issues.

Most people think it was the other way around, that the failed whatever part caused the driveshaft to die....

 

[nailheadpowered]

guess that drive shaft loop looks alot more desirable.

 

[GNVYUS 1]

Sorry to hear and see the carnage, I guess this solidifies my purchase of that Carbon Fiber DriveShaft I saw for $800. :frown:

I don't think I have ever heard of a GN cracking the tranny housing, ever.

 

[nailheadpowered]

were did you see a carbon fiber drive shaft for our cars at? and what kind of hp can it handle.

 

[2quiktocare]

Once you get this trans out and apart, we would be interested in what is damaged inside the trans itself. I have seen several that have had the drive shaft let go and the damage to the case was in the tailshaft area and not that far up on the body. Both of those failures were at the track under full loads. When the shaft lets go, don't be surprised if you see the sprague has gone south from the backlash.

 

[yullose]

I don't think it damaged the tailshaft housing at all... The slip yoke never even left the trans...
I think the trans pan is the only thing holding the trans together. That crack in the picture goes all the way around to the other side. Fluid was running on to the floor out of both front corners of the box...
I'll make sure my camera is with me when Jim finally gets it out and apart.

 

[chris718]

mark dyno load and strip load are totally different.ive seen 4 of those already.2 were in our test car and caused by overspeeding and lifting on the lift at 100 mphour.for some reason the overspeeding of the driveshaft with limited load of the final drive seems to initiate driveshaft explosions and case damage in that area,although i am not sure why.it would prove interesting and rewarding to understand the root cause.

 

[2quiktocare]

I agree Chris, that's why I asked for some info after it was taken apart. Pics would be nice also.

 

[yullose]

Overspeed/lifting may have something to do with it... I know Jim said he was just starting to lift when it let loose...

Here's a pic of the actual run... Looks like it was 134mph in third gear to be exact...

 

[Turbo1dr]

were did you see a carbon fiber drive shaft for our cars at? and what kind of hp can it handle.

Click below for carbon fiber drive shaft. That's what I now have in mine after having 2 driveshafts to let go. I purchased the slip yoke and the differential yoke with 1350 joints. They said the shaft is good until 1700HP.


http://www.pstds.com/critical_link_drive_shafts.htm

 

[Firechicken]

I use a Denny's Nitrous Ready shaft in my car. They say it is untwistable.

 

[JC Turbo]

mark dyno load and strip load are totally different.ive seen 4 of those already.2 were in our test car and caused by overspeeding and lifting on the lift at 100 mphour.for some reason the overspeeding of the driveshaft with limited load of the final drive seems to initiate driveshaft explosions and case damage in that area,although i am not sure why.it would prove interesting and rewarding to understand the root cause.

All this makes me not want to Dyno my car. Any suggestions on how to avoid this problem?

 

[GNVYUS 1]

Here are my aftermarket driveshaft links.

www.markwilliams.com ( carbon for $800 )
www.dennysdriveshaft.com
www.dynotechengineering.com
www.iedls.com
www.pstds.com
www.acpt.com

Turbo1, what did your carbon cost you?

So chris718 and 2quik, do you think that an aftermarket shaft could stop this damage from occuring?

You would think that with the shaft snapping the load would of found its weak link to let loose on and not hurt the casing.

 

[NJVetteGuy]

There was definitely something wrong, the dyno graph should show the hp/torque lines cross at 5250 RPM. You sure it was in 3rd gear?

 

[A. G. Olphart]

Among other things...

Not sure what broke first, but the case is cracked, the driveshaft is in several pieces, the exhaust is junk, and the floor is mangled up pretty good.

The broken driveshaft shows that the load applied as it was twisted apart was counter clockwise (as viewed from the front of the car). IIRC this is normal rotation, and that should indicate that the driveshaft just let go. (Had the tranny locked and inertia unwrapped it, the tear should have gone in the opposite direction... hope I'm remembering old moving fan blades correctly).