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Old 06-10-2007, 08:38 PM
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TH400, What caused this?

I was rebuilding my TH400 out of a parts Jeep I saved, converting it to 2WD to use in my Ambassador but I noticed that it appeared to have been rebuild not too long ago. A lot of the peices still had paint marks on them like they'd have sitting on the shelf at a trans shop. The direct drive clutches almost looked new. BUT, when I took apart the forward clutch assembly, it was toasted! The clutches were worn down to the metal and warped like a somvabich!



Also, one of the ball valves left a mark in the case that looks like it was shot out of a ten pump bb gun with 18 pumps!



Here's which ball it is:



Any idea what caused this? I'm guessing that the PO revved high and dumped it in gear, but I want to make sure it's not an assembly issue so I don't repeat it!

Just for info, I never drove this transmission. I got it out of a parts Jeep. Thanks in advance for any ideas you guys might have!

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Old 06-10-2007, 08:53 PM
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Forward clutch lip seal cut on assembly, too loose clutch tolerances letting the piston overtravel, leak in the forward clutch circuit (rings on the rear of pump), etc.

Find the problem before you re-assemble it. Check the apply piston closely also.

There should be 5 clutches total, make sure there is not too much clearance. It can be fairly tight on the forward clutch clearances. .030-.050" is good to aim for, you can use a .090" thick direct steel to tighten it up.

Wear at the checkball locations is normal and you can omit that checkball on rebuild anyway.
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Old 06-10-2007, 09:18 PM
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Thanks jakeshoe! This is my 4th TH400 rebuild and I've never seen one like this! I assembled the forward clutch assembly (with new steels) to check for clearance and it's nice and tight, .035 was the biggest feeler I could get in there. I have a spare TH400 I rebuilt not too long ago out of my last Cherokee, I could use it's forward clutch if I have too.

Another question, what's the function of that ball? It's the only one that's left a mark in the case, but you don't think it's related to the fried clutches? Thanks again!
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Old 06-10-2007, 09:25 PM
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That checkball is considered non-functional. It is in the direct clutch circuit. If you follow that path that worm passage goes directly to the direct feed in the center support.
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Old 06-10-2007, 09:41 PM
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Great! Thanks!

Matt
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