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Old 05-10-2022, 12:22 PM   #1
Mhussnatter
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broken TH 350 transmission housing where mount bolts go...HELP!!

I have a 1969 short bed lowered 6 in the rear and 4 in the front. Last week I was driving to a show and the rear pinion yoke broke (u-bolt snapped off) and my driveshaft dropped. The truck shook violently and upon further inspection when we got it up on a lift we found that the TH350 housing broke where one of the two transmission mount bolts goes into the housing to mount the transmission in the rear. The bolt apparently ripped right out and took the tab or ear of the casing/housing with it. Anyone have this happen before and how can it be repaired? Is there anyway to weld and then tap and put a new bolt in? Do I need to get a whole new transmission? New transmission housing ? I'm stumped and don't know which way to turn. This repair is wayyyy beyond my abilities and I'm looking for advice. Thanks so much in advance. The last picture of course is from a book showing what the bottom of the transmission housing should look like without one of the ears/tabs broken off

https://www.dropbox.com/s/4ewxsjqvxa...t%201.jpg?dl=0

https://www.dropbox.com/s/jyarqobl4r...t%202.jpg?dl=0

https://www.dropbox.com/s/fdb7e15i4m...t%203.jpg?dl=0

https://www.dropbox.com/s/767v3bkqly...ormal.jpg?dl=0
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Old 05-10-2022, 12:28 PM   #2
body bolt
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Re: broken TH 350 transmission housing where mount bolts go...HELP!!

If it were me I'd look for a TH350 builder, rebuild it and replace it. Or you could pull a Freiburger and zip-tie it in there.

Last edited by body bolt; 05-10-2022 at 12:34 PM.
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Old 05-10-2022, 01:32 PM   #3
Steeveedee
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Re: broken TH 350 transmission housing where mount bolts go...HELP!!

Bummer! I'd take it to a rebuilder. It's possible that the output shaft is bent, and there could be damage internally from when the transmission shifted. I'd also check to see if the motor mounts are still intact, and look for damage to the fan, just in case it shifted that far.
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Old 05-10-2022, 08:59 PM   #4
Accelo
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Re: broken TH 350 transmission housing where mount bolts go...HELP!!

"TH350 housing broke where one of the two transmission mount bolts goes into the housing to mount the transmission in the rear."

Bad news is the fastest, least expensive repair will be to replace the case.
And by the time you pull it and tear it down for the case replacement you might as well rebuild it. Good used thm350 is a crap shoot.

It doesn't look like the transmission is leaking. Not really recommended but you could just install the one bolt and replace the drive-line.
Sounds lame, doesn't ti? However, I lost count of the transmission I have repaired that came in with a de-laminated rear mount.
One bolt has to be better than none? Comes down to the depth of your wallet.

Last edited by Accelo; 05-10-2022 at 09:04 PM.
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Old 05-10-2022, 09:58 PM   #5
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Re: broken TH 350 transmission housing where mount bolts go...HELP!!

There are millions of cars with one bolt holding the trans mount to the crossmember. I've seen many in the '70s, at least. But that's cars, like Novas and such.
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Old 05-10-2022, 10:02 PM   #6
Warrens69GMC
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Re: broken TH 350 transmission housing where mount bolts go...HELP!!

Nevermind, i didn't see the photos
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Old 05-11-2022, 09:05 AM   #7
MARKDTN
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Re: broken TH 350 transmission housing where mount bolts go...HELP!!

Depending on what you want, it could be time for an overdrive upgrade. I could not convince myself to put that back together with 1 bolt, but that's just me. If you want a TH350 then I would find a case/core and have it built. You can bolt in a 200R4 with the same driveshaft. You could go to a 700R4 with the same yoke and a shortened driveshaft. Etc. I am concerned though that you have bigger problems. Did you say you broke a pinion yoke? Are you sure the rear end is OK?
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Old 05-12-2022, 04:12 PM   #8
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Re: broken TH 350 transmission housing where mount bolts go...HELP!!

I saw this on eBay, for $300 you could use the case.

https://www.ebay.com/itm/25548841040...8AAOSwrIxiWD07
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