XJS ( X27 ) 1975 - 1996 3.6 4.0 5.3 6.0

TH400 casing cracked

 
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Old 06-14-2019, 11:00 AM
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Default TH400 casing cracked

Hey guys,

so, I wanted to start to rebuild my TH400, which has been going on for a while, until I checked the case to make sure it was usable and found a crack along the side. Very small. I tried to take a picture but it won't appear. Anyhow, the crack isn't old, as it is totally clean. No ATF had passed by so it must have happend since taking it apart. Water will pass through it, so it is not just a cast error or so. Result: case is dead.

I just dont know how it happend. The case has been sitting on the bellhousing end since taking it apart in the same position. It hasn't fallen over.

Oddly, it seems that the TH400 case seems to be prone to cracking. At least several V8 cast cases have cracks. Not in the same area. So I was wondering: is mine a one off? And why would it happen with no load inside and totally clean?
 
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Old 06-14-2019, 11:10 AM
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Small cracks are safe to weld.
 
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Old 06-14-2019, 11:13 AM
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Originally Posted by Segfault View Post
Small cracks are safe to weld.
It's about 11 cm long... I don't think it will stop going by the length.
 
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Old 06-14-2019, 11:19 AM
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Well, it depends where it is and what's inside of casing. If it is just the wall I'd still say it can be welded. Maybe not a DIY job, better see a specialist.
As for reasons, dunno. Here in Louisiana we have plenty of voodoo witches, evil eye, you know. Some of them may be migrated to Germany after Merkel invited more folks to Germany.
 
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Old 06-14-2019, 11:26 AM
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I've already found some cheapish transmissions I can take apart. Welding would be possible, but I am worried about it carrying on. I would assume it is a stress crack, due to the position and way it is cracking...
 
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Old 06-14-2019, 11:39 AM
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If you can find a new case, I'd definitely go with that. Who knows why it has cracked, temperature changes and age? Possibly an inclusion in the casing that was a stress raiser?
 
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Old 06-14-2019, 12:06 PM
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Originally Posted by Jagboi64 View Post
If you can find a new case, I'd definitely go with that. Who knows why it has cracked, temperature changes and age? Possibly an inclusion in the casing that was a stress raiser?
I know it was not cracked before. It is a clean and fresh crack. So it may have been the winter causing it.

Just wanted to highlight that a transmission fluid leak MAY well be a cracked case... Not always just a leak in a gasket
 
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Old 06-14-2019, 12:14 PM
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Too bad you are in Europe! I have a NEW-IN-BOX (crate) THM400 (3L80) for the 5.3 liter V12.(EBC3654N)
The dealer I worked at was going to throw it in the trash but the parts manager asked me if I wanted it.

Still in the wood crate with the steel bands. I've had it several decades and still can't find a use for it??

Shipping would be cost prohibitive.

bob
 
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Old 06-14-2019, 12:23 PM
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Originally Posted by motorcarman View Post
Too bad you are in Europe! I have a NEW-IN-BOX (crate) THM400 (3L80) for the 5.3 liter V12.(EBC3654N)
The dealer I worked at was going to throw it in the trash but the parts manager asked me if I wanted it.

Still in the wood crate with the steel bands. I've had it several decades and still can't find a use for it??

Shipping would be cost prohibitive.

bob
That would be awesome, but as you said, shipping would be the reason it wouldn't make sense. I can get a case for like 300.
 
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Old 06-14-2019, 01:25 PM
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Originally Posted by motorcarman View Post
Shipping would be cost prohibitive.
Maybe try looking for a air freight forwarder/consolidator? If Daim can do the customs paperwork on his side ( usually easy to do) the cost can be surprisingly cheap. I brought a Rover V8 engine from England to Canada and it cost a lot less than I expected.
 
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Old 06-14-2019, 02:21 PM
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If a large truck shows up I can load the crate onto it.




bob
 
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Old 06-17-2019, 03:44 AM
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Originally Posted by motorcarman View Post
If a large truck shows up I can load the crate onto it.




bob
Great tractor Bob! And again Tha KS for the offer, though I can't get shipping to be in a usable area. So I'll have to unfortunately pass on your transmission...
 
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Old 06-17-2019, 08:54 AM
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Originally Posted by Daim View Post

Oddly, it seems that the TH400 case seems to be prone to cracking. At least several V8 cast cases have cracks. Not in the same area. So I was wondering: is mine a one off? And why would it happen with no load inside and totally clean?
yes, they are... You have a few options. I would drill it out and alumafix it. If it's an 11MM crack drill it out to 13mm, clean and weld it up with alumafix or some other low temp aluminum braze. If the crack spreads during the drill or welding process then you need a new case. If its take the weld and no cracking re-appears metal finish the repair and carry on.
 
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Old 06-17-2019, 10:49 AM
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Originally Posted by icsamerica View Post
yes, they are... You have a few options. I would drill it out and alumafix it. If it's an 11MM crack drill it out to 13mm, clean and weld it up with alumafix or some other low temp aluminum braze. If the crack spreads during the drill or welding process then you need a new case. If its take the weld and no cracking re-appears metal finish the repair and carry on.
It's about 10 cm (4"l long)...
 
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Old 06-17-2019, 11:17 AM
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Now what I think of mine ... I believe I tossed it away after installing the manual. It was taking up space and no-one wanted it.
 
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Old 06-17-2019, 01:30 PM
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Originally Posted by Daim View Post
It's about 10 cm (4"l long)...
still fixable... you will have to drill a 5/16 hole at each end of the crack. Then grind a slot where the crack is and fill with weld. Might work...might not. Good luck.
 
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Old 06-17-2019, 06:11 PM
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Originally Posted by icsamerica View Post
still fixable... you will have to drill a 5/16 hole at each end of the crack. Then grind a slot where the crack is and fill with weld. Might work...might not. Good luck.
Not worth trying. And later on I have it welded, the welder bodges it and I assemble and the tranny leaks... Waste of time and money... Cast pieces shouldn't be welded anyway...
 
 
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