2 steps forward 10 steps back! trany and slip yoke? sorry long

[1st_charger]

OK so hears the deal I've almost got the car ready for this summer. I've got the exhaust all on, got the kick down just about right, its close just had a couple more adjustments to work on! So I take the car down the road about a mile and a half after Ive got it warmed up. Seames to be running great moving along at about 55 - 60 mph running 3000 rpm 383 automatic with 3.91 rear. then all of a sudden boom and i feel the drive shaft bounce off the bottom of the floor. I shut it down as fast as I can and get it stopped. Crawl under to find the slip yoke broke an ear off and dropped the driveshaft. Then I noticed the tail shaft housing on the transmission is busted Ive never seen anything like this I'm thinking the slip yoke broke and that bound up and broke the trans housing. All of the mootor and the trans mounts are still fine nothing separated or torn. have any of you ever seen this or any thing like it? any other thoughts as to what could have caused it?

Thanks!

[Ghoste]

In my case it was caused by drag racing. 

[1st_charger]

Well I wasn't drag racing! but what actually caused the failure? did the engine move to much? did the u-joint fail? did the slip yoke fail? could the torque converter have gone out of it and caused this kind of damage ? just grabbing at straws trying to figure out what went wrong what failed so that I can try to prevent it in the future.

I took the broken tail shaft housing off tonight and turned the tail shaft and it seames to be bent some where as it doesn't turn true. also I was looking at the torque converter and I can stick a finger in the neck and move the little gears or teeth in side of it! Is my converter toast I'm not sure if these should move or not and I don't have another to compare it to.

thanks

[RD]

your driveshaft is spinning really really fast...if something goes bad near your u joint, then the whole system is off balance and will pop whatever is causing resistance in its way to find a neutral force to its kinetic centrifugal energy.  the force that your driveshaft (i.e. slipyoke) was under at that time found that neutrality in your tail shaft housing.  the movement away from the center of gravity at the force it was moving caused your housing to flex in a manner that surpassed its malleable state, hence a crack formed then the breakage.  Your housing was not strong enough to counteract the force of which it was being placed by the outward movement of your slipyoke and driveshaft.


i.e. the driveshaft was in your housing, had to go somewhere really quick, and your housing was too much of a cast aluminum pussy to handle the stress, hence it broke and then you heard the loud bang and about s*** your pants

much easier to fix if it was the rear u joint 

seriously, your driveshaft is a balanced piece.  when your tire goes out of balance you get a huge vibration right? on a driveshaft, if a piece is missing, weight is flow off or a u joint fails (or in your case slip yoke breaks) such a loss of balance is catastrophic and will destroy whatever is in its path, or at least try to.

[John_Kunkel]

Don't assume that the tailhousing is all that's busted, I lost a u-joint at speed and it broke the case along with the tailhousing and bent the output shaft.

[Charger-Bodie]

its very possible that you weakend it sometime when you WERE running it hard and it just held together long enuf to make you wonder

[Ghoste]

John is absolutely right, along with the transmission parts you need to check the driveshaft for straightness and the rear yoke for square.

[1st_charger]

its very possible that you weakend it sometime when you WERE running it hard and it just held together long enuf to make you wonder

I could under stand that if I had run it hard the only miles on the car were a couple of trips around the block in town a trip to the exhaust shop 4 miles one way at 55 not on it hard and 2 trips down the road 1.5 miles one way no faster than 55,60mph thats all the car has been driven! on the the rebuilt transmission and u-joints.

Also tearing it down last night found it did bend the tail shaft and the main case does have a crack in it were the tail shaft bolts on!

[1st_charger]

John is absolutely right, along with the transmission parts you need to check the driveshaft for straightness and the rear yoke for square.

Ok how do I check the rear yoke for square?

[SeattleCharger]

  bummer man, I would be bummed if that happened,   

[1st_charger]

bummed doesn't even come close! 

I found a guy that has 2 big block 727 he wants 200 a piece and said that the cars he pulled them out of 6 months ago ran fine (he runs derby and uses small block). and said that I should be able to just slide one of them in and run it!

I'm not sure weather to go that way or rebuild one with the guts in mine with exception to the tailshaft!

[Charger-Bodie]

i personally would build a totally diff trany

[SeattleCharger]

  Throw in the 200 dollar one, when that dies some day rebuild it, for now you could maybe just focus on getting everything together and working right,  just in case you rebuild it and the yoke fix or u joint isn't quite right yet, then only the old tranny is lost maybe if another big thing happens like this.

[John_Kunkel]

There are a lot of components in a car that get little notice until a failure occurs, for instance I never noticed how really thin the area surrounding the u-joint cup is; this is necessary so that there will be clearance between the componts of the u-joint at high angles of defection.

Considering that the slip yoke and driveshaft ends are cast material, it's a wonder they don't fail more often.