this all happened in one launch

3600 rpm dump at about 3psi boost (2 step)

27*11.5 hoosier quicktime DOT

moser 12 bolt, 3.42 gears

denny's nitrous unbreakable driveshaft, 1350

spec 5 iron

stock gears and shafts t-56

bmr extreme tq arm -3* pinion

ideas?
the last two changes were the tq arm and the clutch
the car did really well last time out with the tq arm before the clutch.

raceweight was over 3700#

broken ring and pinon, broke output shaft, twisted slip yoke

 

Damn it Dave........ we were talking about everything going good and you buying heads and a new turbo and maybe some wheels....... and you were like yeah i can do it when **** doesnt break....... and all this happens at once.......

I was wondering about your 12 bolt and how it was holding up for so long......
Is it just going to take a new gear set to fix it??
What did Dennys say about the DS... Warranty??
Viper output shaft now????
Kyle

 

its possible the rear end locked up when it broke, you will find the weakest leak from the flywheel back reak quick when the rear end locks under WOT. I have even twisted a crankshaft once when a rear broke and locked up at the starting line, also tore the trans right off the back of the motor

 

thats great kp, cant wait to see what else i can find

so far the replacement gears are on the way, no freebie from moser

sending the ds to denny's to have them look over, then decide which slip yoke to put on depending which output shaft goes in the trans

so far looks like the trans will get a g force viper mainshaft and then get a std viper slip yoke on the ds.

spec is also doing some figuring on a different clutch set up.

 

How much is that stuff Dave.....??? Im going to go look at there site now.....
Kyle

 

how much slip traval did your DS have with the suspention loaded?

 

its plenty..ugg. but im having Dave Tiura install the stuff, not g force.

great question hbh, i measured it up per denny's instructions and what i got is what i got. there is right at a half inch i'd say.. (enough room to slide it forward to get the u joint out of the rear end)

the driveshaft and have been running the same length one with the same rear for the past two seasons without incident.

if it was a pinion angle problem, would it be taking out the u joint and not the ouput shaft?

 

well, I guess what I am saying is what was your slip traval with your new TQ arm? BTW, they say that for NA apps 1/2 inch and power adders to he 3/4-1 inch. I would take a guess that you bottomed out the DS into the tranny.

 

new torque arm didnt move the rear any closer.. seems the same to me?

i dont know how the rear could move that far forward on a launch, but im not the expert... and i dont have solid bushings.. good point.

but.. i have always launched the car in the same manner for the last 3 years

when i get the trans back in denny is having me re-measure the stuff. and i will def. keep that in mind.

you are saying broken output shafts are the typical result of not enough slip?

 

wouldn't be the first time that I have seen that happen. Considering the power that your putting out I would like to see at least 3/4. When you talk to Denny again see what he says. The viper shaft would also be a good idea "while your in there".

 

Not enough slip joint will wear the bearings fast in the trans and thats about it, if you couldnt get the driveshaft on it was too tight and I'm sure someone would have noticed that.

Torque arm doesnt move the rear forward or back at all, they are not anchored in the front unless you have a madman, the LCAs do that. All of which has nothing to do with breaking a ring and pinion

 

if slip travel hits 0 the yoke will botom out into the tranny on a launch destroying it.

 

Destroy what? The ring and pinion plus twist the splines in the slip yoke - not a chance. Even with stock LCAs the rear in these cars wont move forward a 1/2 inch and if you dont have a 1/2 travel you wont get the driveshaft in without noticing something is wrong.

Even if it did bottom out on a launch the motor and trans mounts in these cars will let everything move forwatd about a 1/2-1/4 inch so his problem isnt with diveshaft length.

 

um hmm.. Then how come thats exactly what happens with people that install a 12 bolt, run the stock DS and neve check slip travel? I find it very hard to belive that you have yet to see this happen. All of the twisted output shafts, detroyed tail shaft housings. Hell, guy I know just literealy cracked the belhousing of his new TH400 for this exact reason.


Secondly. WHat you are talking about? The rear never moves "forward". The relationship of the rear in level with the tranny changes. When the suspention loads and the rear gets pushed up into the body the distence between the rear and tranny becomes smaller. Thats why there is slack in a driveshaft. why do you think that they recomend different slip travel for different aplications? More power and a heavy hit at launch can even botom out the rear suspention thrusting the DS into the tranny. Considering his 60" thats completly possible. your arguments are sounding like you don't understand how the gemometry of the suspention works implying that the rear is moving "forward".

Now, lets throw out a theory. Old TQ arm could have caused incorrect pinion angle because of the moser. Perhaps on a launch with the old TQ the suspention would go into a bind and not alow full range of movment. Now with the correct setting it can. So that can lead to boom.

Is that the answer? dunno. could it be? sure. Does it help attacking me instead of solving his problem? not really. So lets help.

1/2" slip travel is good for an NA aplication
1/2" slip travel is NOT good for a blown car hitting almost 4 digits of HP
he should have about 3/4" of slip travel on his car to be safe
weather that cause the problem or not doesn't change the fact that he needs it in the future.

 

If MM's tailshaft, housing or driveshaft broke I would say well maybe the driveline angle was way off or the torque arm mount broke on the housing but the rear end breaking has nothing to do any of it IMO.

I fully understand the concept of how it all works and yes 3/4" is recommended even for an n/a car - no argument there. What I am saying is the driveshaft length, even if it was pounded it with a hammer, did not break the rear end.

I have been drag racing for over 25 years and have built cars that have been near 200mph in the 1/4 (196 to be exact) so I have a little clue as to whats going on when a car leaves the starting line. Cant get any simpler then these cars.

Now I cant say if the driveshaft was too long or not but that was not the root cause of what happened which is my only point. I agree that the pinion angle being off will destroy driveline parts, but it wont break the ring and pinion. Now if the end of the pinion yoke was snapped off I would say maybe the torque arm bolts came loose and the rear spun in the car and did some damage. But from what I see and from my direct experience (I have broken/locked up 2 rears a few feet out, a full floater dana and a 9") and from what I see the rear locked up first. At this point I think MM is smart enough to go over everything when it goes back together - I'm not trying to argue

 

I have seen just this happen before from this very cause. The person with the TH400 that I spoke about before. Yes the ring gear shatterd, along with the companion flange, DS yoke, tranny case... everything. After talking to him to find out why I asked him what his slip travel was. When he said he didn't know. When I asked him how he could not have checked after putting a TH400 in he mentioned it being hard to manage the DS into place clearing the companion flange. If I were to "guess" he had about 1/4". Couple that with the T brake and hard launch and be literaly destroyed everything. First he thought just the flange and DS, later found the tranny case cracked, later founf the ring gear detroyed....

The moral of the story... well, I think you get the idea.

considering the information given, DS length is a large concern. It's atleast a problem even if not this problem. My point is that regardless of the cause it's something that should very much be addressed. Weather or not he desides to rebuild the 12 bolt, run a 9 inch, custom fabed housing etc etc it's going to be in his best interest to get the system in good working order to prevent problems.

 

This is some good stuff going back and forth..........

 

Either way, just by looking at the yoke you can see the DS was pretty far in but I will stand by that thats not what caused the rear to let go. But its hard to tell when everything lets go exactly what caused it. I also ripped a TH400 off the back of a motor once when someone forgot to put the clips in the U-joint on the trans yoke and the caps came out and the driveshaft got jammed on just the right spot on the crossmember to stop the whole mess at around 100mph. Tore the trans right off the back of the motor, sheared the flexplate bolts off the crank and locked up the rear as well - was a fun ride. Rear end was just fine after all that thought

Not arguing like I said, just presenting my point of view..

 

not saying you are kp learning a point of view from both sides that i really didnt know much about.

 

I know Kyle, its hard to present things over a the internet at times and no one really knows who anyone else is. If everyone was at the dragstrip analyzing MM's car things would go a lot smoother But thats the fun of the internet.