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Th400 trans brake wont hold


Sam1647545489

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On my car I have a th400 trans with trans brake. When I engage the brake it wont hold the car at all. It rolls forward. Any ideas on what could be the problem. Its a new trans so I dont think the reverse band could be bad already. I dunno though yet. I assume pressure is good, didnt check but I dont see why it wouldnt be.
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th 400 tb requires the removal of 2 seals and relies on one seal. if it tears or swells it looses the pressure its supposed to hold to apply rev. usually if the tale tale sign is if you engage the brake and bring up the rpm car rolls forward. also do a pressure test to confirm before pulling trans for a new seal. yes I know its a new trans but the seal is easy to rip on install.
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th 400 tb requires the removal of 2 seals and relies on one seal. if it tears or swells it looses the pressure its supposed to hold to apply rev. usually if the tale tale sign is if you engage the brake and bring up the rpm car rolls forward. also do a pressure test to confirm before pulling trans for a new seal. yes I know its a new trans but the seal is easy to rip on install.

 

What seal are you talking about replacing

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Figured out how to get it to work. Not sure if this is the correct way or whats going on with it but if I foot brake it alittle then hit the lock it will work flawlessly. Is this a common problem or tactic to use. It seems like at idle its not building enough line pressure to get it to hold?
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From what I've read some people have to bring it off idle, and some don't. I just read more into it today. Although some here say u may wanna check it with a gauge

 

This makes sense, depending on how much line pressure the trans has at idle. Some with relatively stock pumps and such may not make much at idle. I've never built a trans with aa break in it, but I'll bet there are a coule supporting mods that make it work better. Hopefully its not a big deal and you can get it all working.

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