Thread: huge crack in transmission!!?????

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alright well this is in my 1950 chevy pickup.. and turns out i was just cruising on the highway all day and finally got home later in the night and it was makin a tickin sound like a flywheel bolt was comin loose or sumthing so i shut it down and checked them all and they were all tight so i was lookin around for what it could be and looked at the starter area and noticed a HUGE crack just about all the way accross the bellhousing.. starting at the starter.. going back about 3 inches.. strait up to the top (middle) and about 5-6 inches further down the other side.. i couldnt believe it ... does anyone know what this could have been???

all of the tranny to engine bolts were tight so it wasnt that... mounts maybe?? also i know that the tranny is shot because of that so im wondering on any other suggestions for trannys.. like the 4l80e or the 4l60e??? what other mods would i run into with adding one of these two> also would it be worth spending the money on like a tci tranny... for the warrenty or just keep spendin a couple hundred bucks each time this happenes... heh.. but if anyone can help that would be great...

btw... the tranny is a 700r4 behind a stout 283 w/ 410 gears..

Are you running solid motor mounts?

still the stock 1979 elcamino motor mounts that i know of

There may have been enough twist in the old Chevy frame to put the case in a bind.

i wouldnt think it would crack like that cuz of twist because it has an elcamino subframe on it.. what would u reccomend doing??

I would think either something is binding or the frame has a huge amount of flex in it... I've seen this happen a few times, in one case the guy had the stock rubber cushioned motor mounts, and a solid tranny mount. Your truck has an Elky subframe on the stock rails??? Is it a good strong weld with adequate fishplating and gussetting?

well we had a guy put it on... he boxed in the frame about a foot behind the subframe .. but other than that .. its still got the stock elky mounts and a stock used tranny mount.....

Here is the text of GM service bulletin 02-07-30-024
Obviously, it is not for your specific vehicle but
it may give you some ideas

Diagnosing the cause of a cracked or broken transmission case requires additional diagnosis and repair or a repeat failure will occur.
A cracked or broken transmission case is most often the result of abnormal external torsional forces acting on the transmission case. If none of the conditions listed below are apparent, an internal transmission component inspection may be required. Repairs of this type may be the result of external damage or abuse for which General Motors id not responsible. They are not the result of defects in materials or workmanship. If in doubt, contact your General Motors Service Representative.
The following items should be considered:

• It is important to inspect the vehicle for signs of an out of line condition, impact damage of foreign material to the following components:
• The transmission
• The engine mounts
• The transmission rear mount and crossmember
• Vehicle frame damage that alters the front to rear alignment of the driveshaft
• The drive shafts (both front and rear)
• The wheels (caked with mud, concrete, etc.)
• The tires (roundness, lack of cupping, excessive balance weights)
• The transfer case (if the vehicle is 4WD)

• A worn or damaged driveshaft U-Joint has shown to be a frequent cause of transmission case cracking, especially on vehicles that see extended periods of highway driving. Always inspect the U-Joint condition when diagnosing this condition.

• For driveshaft damage or imbalance, Inspect the drive shafts (both front and rear) for dents, straightness/runout or signs of missing balance weights. Also, inspect for foreign material such as undercoat sprayed on the driveshaft.

• The driveshaft working angles may be excessive or non-canceling, especially if the vehicle carrying height has been altered (lifted or lowered) or if the frame has been extended or modified.
• Damaged or worn, upper or lower rear control arms or bushings.
• A rear axle that is not seated in the rear spring properly (leaf spring vehicles).
• Broken rear springs and or worn leaf spring bushings.

In some cases, the customer may not comment about a vibration but it is important to test-drive the vehicle while using the electronic vibration analysis tool in an attempt to locate the cause of the etorsional vibration. Refer to the Vibration Diagnosis and Correction sub-section of the appropriate Service Manual for more details on diagnosing and correcting vibrations.

Check the flexplate for cracks. That can cause enough vibration to crack a case. Also, check the U-joint phasing, if they are out of whack it can vibrate enough,too. Not all vibration is at a frequency that is easily detected, and thats the ones that do all the damage.

u think that the driveshaft off ballance could have done all of that??? cuz the flexplate is good.... and also i had a th400 tranny in there before i threw in the 700 and the 410 gears we had a local welding shop cut it down about an inch or whatever the size was .. .(duno the right size now) and they welded it up and everything.. and there "was" heh a slight vibration about the 45-60 mph zone... and that happened after the new tranny

I've seen this on 2 late model G.M. pickups with 700r's at my shop, of course I don't deal with tranny's but the shop I send em to say's he see's it a lot,but gave no explanation.....

I would try to find a stock driveshaft the right length. Most wrecking yards have a large inventory of them, just look through the stack with a tape measure.
Your trans could have been cracked a little in its previous life, and just broke completely after you installed it. The joys of used parts!