th350 broken housing from ear to ear

clutch92rs

Amateur Racer
Feb 24, 2004
176
0
0
glasgow, kentucky
I just recently upgraded my 79 malibu to a 383 that dynoed 562 hp and 500 ftlbs torque. We got everything set in and put the new driveshaft in that I just had cut. We were running around on bald street tires and torqued hard on it a couple times. The next morning I got the car out and notice a small vibration. I checked and under the car the transmission housing has split from one ear to the other. I am not sure what would have caused this. I am just looking for common causes to begin diagnosis and checks. All help appreciated.
 

Grcrygtr44

Frequent Racer
Feb 1, 2013
421
0
0
Ontario Ny
Weak or broken trans mount. Or driveshaft to long that it bottoms out in tail shaft when u jump on it. But u said u just had it cut down so that's prolly not it unless it wasn't enough. Or if your bushings in the rear suspension are weak that it's allowing too much rear end rotation that it still pushes the shaft into the tail shaft. My buddy had a similar problem, broke 2 glide cases until finally come to find out, he had measured the shaft when the car was on the lift (rear suspension hanging) which was the mistake but not thinkin about it when he did it. Just a cpl ideas. Good luck
 

clutch92rs

Amateur Racer
Thread starter
Feb 24, 2004
176
0
0
glasgow, kentucky
Thanks....I used dennys driveshaft kinda as a guide for measuring for the driveshaft. I had it on a drive on lift so that it would be loaded on the suspension. I got like 55.5 from the tailshaft to the end of the pinion yoke. does that sound reasonable
 

Purcell Racing

Weekend Racer
Jun 10, 2011
71
0
0
Mineral Wells, Texas
Broken trans or motor mount. Or maybe not strong enough to handle the power if they're rubber
 
Excessive twist or flex in chassis will break transmission cases in addition to everything else everyone listed. Check your body mounts. If they're broken, rotten, etc., then you'll need to replace them to help prevent excessive chassis twist and flex. Also, check for frame rot will you're under the car.
 

clutch92rs

Amateur Racer
Thread starter
Feb 24, 2004
176
0
0
glasgow, kentucky
This is the first time it has happened. From the last setup to this setup, the only things changed were motor and driveshaft. I was on street tires went it happened. I figured it would spoke the tires before it bound up enough to break anything. I am going to look at the mounts and purchase a trz ARB. I gotta double check all my angles at pinion and tailshaft. Then i believe i am going to double check that driveshaft. I used a template from another website to get my measurements. I plan to ?stick the slip yoke all the way in the tailshaft and pull it back about an 1". Then measure that. Does that sound about right
 

Grcrygtr44

Frequent Racer
Feb 1, 2013
421
0
0
Ontario Ny
Sounds like the shaft might b the culprit. And to answer ur question- Depending on how long the yoke measures but IMO, 1" from bottom doesn't sound like quite enough. As long as u are in tail shaft a little more than 1/2 the length of the yoke, u should be safe. But it also depends on suspension bushing style(rubber, poly, or solid) pinion angle, chassis flex, etc etc. AND unless u have reinforced the rear upper and lower control arm mount brackets, u may want to check the holes that the bolts go through Becuz they can be egged out. The holes on my lower arm mounts were so bad they allowed 1/2" of play! Just a cpl ideas for ya! Keep us posted!
 

clutch92rs

Amateur Racer
Thread starter
Feb 24, 2004
176
0
0
glasgow, kentucky
I am gonna go back through pretty much everything that was mentioned. I had never had problems til this 383. I know it is makin more hp than my last setup. I always used the philosophy that it wasnt broke so don't fix it. Now i believe i may have neglected a few things that have came back to bite me. It will extend the driver side shock to its limit even on street tires. Body flex may be part of my cause. I know i can remedy that quick. Probably q good thing i have a couple extra th350 that are in need of repair laying around.
 

Grcrygtr44

Frequent Racer
Feb 1, 2013
421
0
0
Ontario Ny
I have the same outlook on most things but Preventative maintenance can save u money and a headache in the long run. I didn't start checkin things on my wagon until I found that my upper balljoint hardware was finger tight. I'm assuming from wheelies. Now I give er a solid once over at least once a month. Mainly becuz I race it every wknd and run 10.40s so I definitely want to make sure it's safe. Good luck and let us know what ya find out
 

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