driveline gurus....cracking tailshafts.

[aggie97]

So, some time in the last two years, the tailshaft housing on my 03 Cobra T56 cracked along what looked like a casting line from the front of the shifter, and down the passenger side of the housing. I bought a "seasoned" one from D&D which was cleaned and had been checked. simple job to install and throw trans back in the car.

Fast forward to last event.

Trans started making grumbling noises as a piece of cleaning media (small piece of ceramic) got fed through the trans. It was used to clean the tailshaft housing. I found 2 before I installed it, but somehow missed the third. Anyway, sent the trans to liberty to have it faceplated and they tell me the tailshaft housing is cracked...again.

Need some insight what might be causing this. I think the driveshaft might be 1/2" too short but seriously, how is this happening? There are no "major" vibrations from the driveshaft. They all wobble a little at 150mph. Am I missing something with driveline angles? I am not doing anything out of the ordinary here as it should be the same setup in just about every mustang on the road and why did this start all of a sudden after this setup has been in the car since 2005?

<---Lost at this point.

[fastwhite99gt]

Make sure the driveshaft isn't bent. It can cause enough wobble on one end to break stuff, but not really feel it.

[kobuzz]

I've seen a few broken trans cases in my time. One from a driveshaft that was too long but a handful from chassis flex. Is this in a street or track car? what type of motor and trans mounts? Solid/rubber or urethane? Why do you say the driveshaft might be too short? How are you measuring?

[shumpertdavid]

Second on possible driveshaft balance\bent issue, I'd have it checked.

[thesource]

Inspect your yoke closely. It is very possible that the splines are twisted mid way and not allowing it to compress under acceleration like it should. This will crack the tail housing.

[NoClassic]

What type of engine and trans mounts are you using?

[Sleeper]

Inspect your yoke closely. It is very possible that the splines are twisted mid way and not allowing it to compress under acceleration like it should. This will crack the tail housing.

This.

[Gasser64]

This.

Yep. Exactly what happened in my old firebird

[aggie97]

I am pretty sure the yoke would slide in further as it had to go forward to get the DS out...but it's possible.

One of our instructors owns a DS shop down in San Antonio and he and I discussed the issue. I sent it home with him to take a look at this week and see what he finds. My bet is it is bent or wobbling and causing problems. the skewed splines could be the case as well....I am going to confirm with liberty that the output shaft is fine as well.

[thesource]

The output shaft is probably fine. The twist in the splines doesn't have to be extreme either. It just needs to be enough where the yoke cannot fully compress as needed. This puts the tail housing in a bind and will bust it up.

[shumpertdavid]

The output shaft is probably fine. The twist in the splines doesn't have to be extreme either. It just needs to be enough where the yoke cannot fully compress as needed. This puts the tail housing in a bind and will bust it up.

An Addition to this:

Being twisted a slight amount would still allow it to slide in and out freely for removal, but add great strain and stress when you have the driveline loaded under power and it needs to compress.

While I have no seen this in my experience with general auto repair, I could see how this could be a possibility in high horsepower and heavy / hard use instances.

[aggie97]

An Addition to this:

Being twisted a slight amount would still allow it to slide in and out freely for removal, but add great strain and stress when you have the driveline loaded under power and it needs to compress.

While I have no seen this in my experience with general auto repair, I could see how this could be a possibility in high horsepower and heavy / hard use instances.

that was going to be my question as to how common is this? Not like I am doing drag racing or standing starts....however, something has changed since it was all installed in 2005. I may have another driveshaft built with all new parts and start from there. I should hear back from my DS guy today or tomorrow.

Thanks for all the info.