Tranny case cracked

[Mopewbie]

What could have cause this?

440 727
I found out the kickdown was disconnected, no idea for how long.

Thank you.

 

[493 Mike]

I would start with drive shaft straightness, balance, and angle.
Mike

 

[Dave6T4]

I agree. Something wrong with the driveshaft. A friend of mine was racing his 340 Swinger at the local dragstrip. He said he felt a real bad vibration just before his transmission broke. The tailshaft housing broke just like the picture. We found that the front U-joint had somehow spit one of the bearings out, putting the driveshaft seriously out of balance. This all happened at the top end of the 1/4, and dumped fluid all over the track. It was violent enough that it jerked the engine on its mounts, and the fan went into the radiator. My friend has never gone down a track, since.

 

[Mopewbie]

I agree. Something wrong with the driveshaft. A friend of mine was racing his 340 Swinger at the local dragstrip. He said he felt a real bad vibration just before his transmission broke. The tailshaft housing broke just like the picture. We found that the front U-joint had somehow spit one of the bearings out, putting the driveshaft seriously out of balance. This all happened at the top end of the 1/4, and dumped fluid all over the track. It was violent enough that it jerked the engine on its mounts, and the fan went into the radiator. My friend has never gone down a track, since.

Wow. This car shakes a bit in speed, maybe a bit too much. That's probably why.
No idea for how long it's like that, i always check oil level.

 

[icetech]

Wow. This car shakes a bit in speed, maybe a bit too much. That's probably why.
No idea for how long it's like that, i always check oil level.

yeah, only takes a little vibration to break a trans case like that.. especially with how long they are..

 

[bigbluedodge]

My Charger did that twice before I found out the motor mounts allowed the engine to twist a lot and the pinion angle was way off. I reset the pinion angle to 7 degrees down and made a strap to prevent the engine twist and it never happened again. (the car was going 11.50 in the quarter)
I honestly don't know which fixed the problem, but the pinion was WAY off.

bry

 

[Mopewbie]

I know I have to replace and find what caused thebissue but is it ok to drive like that? (Pike I've been doing so far without knowing it)

 

[493 Mike]

I first learned about driveline angles in 1970 after braking two extension housings and a bell housing! I had a 63 Savoy with a 59 413 and "cast iron" torque flite. Some of my dad's buddies did the swap for me while I was at school. I was studying drive lines at the time!
I really wished I had swapped in a later model crank shaft and aluminum TF.
Mike

 

[Mopewbie]

I first learned about driveline angles in 1970 after braking two extension housings and a bell housing! I had a 63 Savoy with a 59 413 and "cast iron" torque flite. Some of my dad's buddies did the swap for me while I was at school. I was studying drive lines at the time!
I really wished I had swapped in a later model crank shaft and aluminum TF.
Mike

Time for me to learn about it, apparently.

 

[Dave6T4]

Are you kidding? How do you keep fluid in it?

 

[Mopewbie]

Are you kidding? How do you keep fluid in it?

No idea, but it's full!
Had to remove the oil stick housing and had loads coming from the top.

 

[Black_Sheep]

The previous owner of my GTX did the same thing, it was blamed on a bad driveshaft. Whoever “repaired” it did a lousy job and I ended up getting it re-tubed because the runout was still way out of spec…

 

[Black_Sheep]

I recommend putting a new bushing in the replacement tail housing before installing it FWIW…

 

[MWbirdLOVER70]

I did that once and it was a bad u joint at the track. Nursed it home 2 hours and had to fluid along the way. My buddy was a trans man and managed to leave tranny in the car and replace the tail shaft in. Kickdown linkage controls governor pressure. Be Leary about wiping out the trans

 

[Cranky]

Lockdown linkage controls governor pressure. Be Leary about wiping out the trans

Kickdown linkage?

 

[MWbirdLOVER70]

Kickdown linkage?

It moves back and fourth and increases and decreases line pressure. My trans buddy taught me about this in the 80’s. I believe shift kits not applicable but I could be wrong on that part

 

[MWbirdLOVER70]

Won’t cause case to crack but will affect shift points also

 

[Cranky]

Won’t cause case to crack but will affect shift points also

Well, if you shift manually, shift points won't be affected because most who do shift manually is well past what the kickdown lever allows. IE, above what the KD will do if that makes sense....

 

[1STMP]

What could have cause this?

440 727
I found out the kickdown was disconnected, no idea for how long.

Thank you.

View attachment 1639717

View attachment 1639718

View attachment 1639719

I would also check how
much upward travel there
is at the pinion snubber.
Jack the pinion up and note
how far up the travel is.
While you have it jacked to
it's highest point, look at
the front yoke and see if
spline engagement on the
trans tailshaft is within
specs. Rapid vertical forces
at the trans shaft can have
drastic effects, caused by
wheelhop. This may also
point to weak rear springs
if the pinion moves without
lifting the rear of the car.
If the pinion does move
it's changing u-joint angles
under harsh conditions
with forces applied.
Been doing any burnouts
lately?

 

[MWbirdLOVER70]

Well, if you shift manually, shift points won't be affected because most who do shift manually is well past what the kickdown lever allows. IE, above what the KD will do if that makes sense....

li do the same with my automatic but KD is still hooked up and travels with the carburetor movement ( forward/backwards ) so maybe his is disconnected down below and never noticed on top side. KD linkage is operated off carb stud and travels via the rod ball crank another swivel point and another rod on the transmission. So shifting auto or manual it’s still moving because of carb accel/de eel but all drpendent on the linkage being hooked up. No linkage no travel no increase or decrease in line pressure which eventually destroys transmission