Not really the first post I was looking to make, but, well...

Little info on what happened and the car.
It had 2.73s. I put 3.73s in it.
It's got an ms4 cam, some head work, some trans work and according to the receipts a vigilante 3800 converter. (The damn thing never flashes more then 2400 or so)
So my dad and I were going to the tuner to get some Dyno time.
We made a hit from 70 to 130 maybe.
Well around 6300 or so I felt a pop and then a big vibration.
I got out of it and saw smoke trailing.
When I slowed to around 50 the vibration and smoke went away.
This was Sunday so I dropped the car off and waited for the call.
Told him what happened and he got a new housing and put it on. He's got it strapped on the rollers and doing some drivibility tuning... Just cruising.
Then out of nowhere... pop.. It breaks it again.

The car has the factory TA, and steel driveshaft.
So why did it break to begin with and what's really broken now.

Anything will help.
Thanks guys

 

First... Most likely the reason the torque-converter stall-speed is lower than advertised is because of your camshaft...
I bet that your engine is absolutely terrible at producing low RPM torque... This will drastically lower the achievable stall-speed.
Should you wish to keep that camshaft; I would look to raise the compression ratio by 1.0 to 1.5 over the current ratio.

Next... What carrier did you install with your new ring and pinion set?
What differential do you have?

Last... Most of the time; when this type of failure occurs it is do to drive-shaft damage or imbalance...
Or possibly differential/ tire vibrations...
Incorrect torque-arm geometry could also possibly be an issue.

Good Luck!

O! and Nice Name... **** YOU TOO!

 

I just had this happen to me and attribute it to vibration due to the junk stock steel drive shaft.
I was going 145 mph at a road course event and did massive amounts of damage and o boy was that a sketchy ride till I came to a stop lol.

The stock steel driveshaft is just to heavy imo to sustain those kinds of speeds.
I don't have the torque arm mounted on the tail shaft but that is doing you no favors.

 

I'm going to do some more research on it, because even when I load the converter the wheels will start to spin around 2200. It pulled a 1.93 60 with 2.73s and only a 1.86 with the 3.73s.
12.86 to a 12.77. something is definitely going on, but that's a different discussion.

I bought a 3 series Detroit True Trac.
My tuner did mention that the stock steel driveshaft many be out of balance. He's going through it to make sure it didn't take out the bearings on the output shaft.

 

Most of the research I've done and what I've seen is pointing to the steel shaft.
I'll have my guy see if he can check it out.
I tell you, the Speedo was buried. That was the first time I've run it that fast. It definitely puckered me up. Then I saw smoke and my stomach sank lol.

Relocating my TA is on the to do list, just wasn't planning on it now.

 

You broke a tailhousing...and just replaced it without finding root cause the first time? interesting...especially since f body tailhousings aren't the most common thing out there.
Check all the things listed above...but I'll add checking trans and motor mounts to the list.
If you have a solid (or stiff poly) trans mount and stock engine mounts...you aren't doing yourself any favors.

While you have the tailshaft off again...also check the output shaft on the trans. Make sure it's not bent/stress cracked, etc

 

Well no, not exactly.
It broke on the way to the tuner. He put another one on to kinda diagnose it. He was cruising around 50 when it started vibrating, then pop.

He's checking on the output shaft, so hopefully it's ok.
It does not have poly mounts, and the TA is also factory.

 

post a picture of the break

 

I tried to post a pic, but it said something about a moderator or something. I didn't pay that much attention after I submitted the post.

 

Get a new trans mount. replace both U joints. Have the shaft balanced.
Any decent local driveshaft shop should be able to balance it for like $50
U joints and the mount are cheap.

 

He didn't get a chance yesterday to check the run-out on the output, but what is the likelihood of it being bent.
He's doing poly trans and motor mounts, and I ordered a relocation bracket with TA and looking at a replacement DS.
any suggestions there?

 

Looks like you're changing enough things and throwing enough money at it to not know what really fixed the issue...but it will be fixed.
I think driveshaft balance and trans mount is all that is needed. U joints for insurance. if you want new motor mounts and a new driveshaft, then it will probably clear itself right up.

Not likely at all to have a bent output

 

Which is what I didn't want to do right now: I already was going to buy them, just not now. Although, I've told him to have the DS checked, and if it can be balanced (providing that's the issue) then I'll have that put back in for now to get me going. If it's too bad or questionable I'll replace the DS and I'll install the other parts at my leisure.

 

Is the drive shaft original?

If it's not and was too long it can bottom out on the output and shove it into the trans and break all kinds of things, even the case.

 

Yes it's the stock steel shaft. He's going to check the balance on Tuesday.