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Old 09-04-2012, 08:08 PM   #1
alkynova
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Default Th400 rear servo leak

I air checked my rear servo after I rebuild my transmission. I sanded the servo cover to make sure it's flat and put on a new metal seal. It still leaks. I torque the bolts to 18 ft pounds as my manual said. Is there any trick I can do to seal this up. I have some copper head gasket spray I was thinking of using but don't know if that would be bad. Looking for suggestions. Thanks
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Old 09-04-2012, 09:33 PM   #2
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Default Re: Th400 rear servo leak

Is the case flat?Is the cover fully decked flat on a true parrallell surface?Did you use coarse paper?If so it may be flat but have dips in between the flat surface.Some air will leak but very little.How much is leaking?Big blast of air?
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Old 09-04-2012, 10:00 PM   #3
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Default Re: Th400 rear servo leak

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Originally Posted by chris718 View Post
Is the case flat?Is the cover fully decked flat on a true parrallell surface?Did you use coarse paper?If so it may be flat but have dips in between the flat surface.Some air will leak but very little.How much is leaking?Big blast of air?
It's leaking in a few spots between the bolts. I can see very little bubbles
And can feel air breeze. I I'll check the casing to see if it's flat. I sanded it with 150 grid lightly. I can't see any deep groves or anything
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Old 09-04-2012, 10:02 PM   #4
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Default Re: Th400 rear servo leak

Does the band apply with light air pressure? What you're seeing is most likely normal.
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Old 09-04-2012, 10:23 PM   #5
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Default Re: Th400 rear servo leak

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Originally Posted by alkynova View Post
It's leaking in a few spots between the bolts. I can see very little bubbles
And can feel air breeze. I I'll check the casing to see if it's flat. I sanded it with 150 grid lightly. I can't see any deep groves or anything

Sanding yes, but is it flat?

Sand it on a piece of glass and use coarser paper.
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Old 09-04-2012, 11:26 PM   #6
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Default Re: Th400 rear servo leak

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Originally Posted by E.R. Racing View Post
Does the band apply with light air pressure? What you're seeing is most likely normal.
It sounds like it is. I can see the shaft budged a cunt hair as I apply air
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Old 09-04-2012, 11:30 PM   #7
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Default Re: Th400 rear servo leak

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Sanding yes, but is it flat?

Sand it on a piece of glass and use coarser paper.
what's coarser should I use? I
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Old 09-05-2012, 12:51 AM   #8
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Default Re: Th400 rear servo leak

Sand it agressively on a machined flat surface. Apparently the surface you sanded your cover on was not flat. Install a new steel gasket and its over (no sealers are used here). Small leaks are no concern but if done properly will not be there.


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Old 09-05-2012, 01:00 AM   #9
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Default Re: Th400 rear servo leak

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Originally Posted by alkynova View Post
what's coarser should I use? I
60-80 grit.
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Old 09-05-2012, 01:01 AM   #10
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Default Re: Th400 rear servo leak

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Originally Posted by alkynova View Post
It sounds like it is. I can see the shaft budged a cunt hair as I apply air
blonde red or black?
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Old 09-06-2012, 08:10 PM   #11
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Default Re: Th400 rear servo leak

i am suprised no one makes a biller servo and new biller cover ??
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