My Th-350 cracked behind my BBC, i have a rubber tranny mount, im stumped on how this happened, just bought a new tranny, really don't want this to happen again any pointers?:(

First thing that comes to my mind is that BBC engine mounts, move the motor over some. Have you looked into this? Just where is the crack? Exten housing?

If you craked it around the bellhousing,check the driveline angle.Pinion angle is the worst culprit,and a driveshaft that is too long is second.

Cracked from the top od the bell housing down to the last bolt hole

i have SBC motor mounts

is it for your 69 camaro?? get the moroso big block mounts for the frame and engine and use a good trans mount, moroso offers one also..make sure the driveline is straight..

Rubberized isolating pads or solid mounts?

If engine has solid mounts, use a flexible trans pad.
If you really must secure the eng/trans combo, use a mid-motor plate and remove the trans crossmember.

Logan,
If it cracked around the bellhousing, make absolutely certain that you get the driveshaft checked for straightness and balance. I know of at least two cars that had similar problems and it turned out the driveshaft was the problem even though you could not feel any type of vibration in the car.

I didn't have the driveshaft hooked up at the time, it was the first start up of my new motor

I didn't have the driveshaft hooked up at the time, it was the first start up of my new motor

It cracked just by starting the engine & NOT under power?

Ya you have smoething wrong if it cracked on engine start up. You might want to try new motor mounts. Is the engine flexing much?

This is odd but goes back to correct frame mounts . BBC stands mount motor off to side but without drive shaft installed, this is strange. With motor side mounts and rear trans mount supporting unbolted to crossmember, where do the trans mounts line up at?

Could the case have had a crack in it, before? Any chance of one block dowel being off set, to the opposite direction and when you tighten down the case, you have a spreading tendency of the bell area on the case?

How about you didnt have the convertor in all the way?Next time bolt the engine to the trans first,and make sure the trans goes all the way against the block from top to bottom before tightening the bolts.After that make sure the convertor spins free after the trans is bolted to the engine,then bolt the convertor to the flexplate.I have had engines that were so out of line before the trans mount was bolted in that you had to use a pry bar to push the trans over to get the mont bolted in,and the trans doesnt break.If this broke during startup I am betting that the convertor wasnt in all the way,that or the trans was cracked from before you installed it and you didnt catch it until it was bolted up.

Good luck.

The converter was spinning freely when we had the car up on the lift, i could spin it with my hands. I didnt put the transmission into the car though, my dad did, so the converter could be a problem. I was told that the SBC mounts, and BBC mounts are different but it doesnt matter if you run either, or with a big block? Im thinking that the motor was in a bind, we started it up and gave it a few revs after warm up and break in, lifted the car and there it was Big CRACK! My dad and i both inspected the trans for cracks prior to installation and didnt see any. The transmission that came with the car was even cracked.....So you guys think BBC motor stands? The crossmember mounts in the stock location and eveything the bolt holes were right on, but like i said i didnt put it in so...

More than likely if your converter wasn't all the way in,you would've broken the front pump gears,and you would'nt have been able to spin the converter. If you unbolt the converter can you slide the converter forward at all?

Are both your dowl pins in the block?

Does the pilot hub of the converter fit in the crank correctly?

When you installed the Trans mount bolt's,did you have to pull the trans to the side to get the bolt's to line up with the crossmember?

something aint right here?? start with the right mounts,make sure the conv. is in all the way and the flywheel bolts are tight and make sure you have two dowel pins and the bellhousing bolts are not stripped??

My transmission mount is rubber, would a solid tranny mount be of help

I would never use a solid mount on a trans. (except if it were in a chassis with solid rear suspension and a coupler rather than a drive shaft). I know there are people using them and getting by, but I'm just saying I would never go that route.

is it possble that what you guys are saying that the SBC motor stands have the tranny in a bind when we suck it down to the crossmember? Everything lined up though is where im stumped?