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Old 09-26-2006, 07:51 PM
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TH350 Bellhousing Broken

Hi, I'm Brandon and this is my first post on hotrodders forum. I was unable to get a satisfactory answer on my situation from other people/forums, so I thought I would give you guys a try.
I have a 91 S10 with a 350 making somewhere between 250-350hp, estimated (vauge, i know). Stock rear end, no slicks run with this setup yet. I don't even know how or when it happened, but I took the truck to have a posi installed, and the fella told me I had a cracked bellhousing. He suggested swapping transmission cases, and having him build a custom, more rigid trans crossmember.
That didn't make sense to me, since the tranny rides on a rubber mount that flexes regardless! So, I had a look at it myself and it is cracked pretty badly. I plan on removing the transmission from the truck later this week to determine if it just so happens to be cracked back into the case or if a JW Ultra-bell could fix it.
However, if there's one thing i've learned on this project, it is to figure out what caused the problem, not just fix the broken parts and try again. So i was wondering what is the most likely culprit? I've heard it's pretty common with th350's, with their thin bellhousing castings. I also know i have a fairly bad driveline misalignment (motor and rear not in phase) because of a bad vibration. I figured that may have contributed to it, but I'm no pro. That will be looked into immediately since i know how to check and correct this problem now (current student at UNO).
So bottom line, what's the most likely cause of the broken bellhousing? Should I try another stock case, or fork out the $230 for the JW Ultra-bell? Anything else wrong that I could be overlooking?

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Old 09-26-2006, 09:17 PM
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Did you use the side engine mounts when you put the V8 in or the front of the block ones? Cuz it sounds like you used the front engine mounting points. Using the front mounting points and the rear of the tranny causes the bell housing to be stressed. Even a lo po motor like this will cause bell housings to break.

If you used the side mounts, your tranny may have been stressed before you got it and you get to reap the problems.

IMO, your case is now JUNK. It could be welded back but there are sufficient trannies available for rebuilding.
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Old 09-26-2006, 10:47 PM
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I didn't know about any front mounting points. I used the standard frame mounts that most vehicles i've ever seen use. Three bolts hold a mount to the block on both sides between 3&5 and 4&6. Then the frame mounts are bolted to the crossmember.
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Old 09-26-2006, 11:03 PM
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The most likely cause from what I've seen is a torn tranny mount. Have you taken the rubber mount out yet? If not , get under the truck and push straight up on the tailhousing. I cracked a case on a vette that I put together last year we welded it up and have no problems to this day. If you go that route be sure whoever welds it is experienced with aluminum. Good luck with it.
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Old 09-28-2006, 02:07 PM
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Solid Mounts or rubber mounts?
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Old 09-28-2006, 08:06 PM
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ok, i just got the transmission out tonight, and took it to a fella who will swap cases for $50 including the case. If the front pump is torn up, it'll be another $50, but those are really good prices. He also is going to get me a new transmission mount, because it was definitely in need of replacement.
Yes, all mounts are rubber. The frame mounts are new 2.8L v6 mounts, and engine mounts are the stealth ones. The trans mount is rubber as well obviously, and it's going to be new.
I also checked my pinion angles before removing the trans, and the tailshaft and whole motor is pointing down about 5 degrees, and the front of the rear end is also pointing down about 6 degrees. I'm not exactly sure what i'm doing, but i know thats exactly wrong. So i'm going to stack a lot of shims under the transmission mount to lessen the downward angle of the engine/trans, and check again. I may add some angle shims under the rear axle to point it back up a couple degrees.
what do you guys think? am i on the right track?
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Old 09-28-2006, 09:29 PM
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You really need to ck it more accurately. Question,,how did the diff end up pointing down? Never seen one like that before. May be easier to have the spring perches cut off and then re-set it and weld em back on.
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