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Old 05-02-2018, 09:18 AM
70Chev 70Chev is offline
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Name: Darren
Leaking Turbo 350 pan

Hi guys,

Looking for some advice please? I recently bought an alloy finned pan for my TH350 transmission. It came with a rubber gasket. I fitted it up, filled the transmission and all was good. After moving the car a couple of times the transmission developed a significant leak from the pan, with fluid seeming to leak out of the bolt holes.

I bought a cork pan gasket and changed it over. Filled the tranny and all good. Then, moved the car and it has started leaking again from what appears to be around the bolt holes.

I didn't use a torque wrench to tighten the bolts, and I don't think I've over tightened them, just snugged them up. Anyone got any experience with this type of thing?

Thanks in advance.

Darren
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  #2  
Old 05-02-2018, 04:18 PM
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jaywildone57 jaywildone57 is offline
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I had a similar issue, my th400 would leak overnight because after startup the fluid would drain out of the converter back into the pan and then leak. Found it to be leaking out of the speedo housing. Some also leak out of the dipstick tube which has an o ring or even the selector shaft.

If this could be the problem with yours, wipe all the oil off then place chalk around the suspected area and wait and see. Look for the highest leaking point.
Is yours a standard volume oil pan?

Cheers.
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Old 05-02-2018, 04:37 PM
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cluxford cluxford is offline
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Been there. My first deep pan leaked like a sieve out the bolt holes. Tried everything - tightened, new gaskets, different gaskets...everything. Then I punched a hole in it on a speed hump. Changed to a shallow pan. Rubber gasket. Has never leaked. Sorry I know this does not help.
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Old 05-02-2018, 06:51 PM
Geoff 4 Geoff 4 is offline
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If you want to seal it....& never worry about it again, use silicon only, no other gasket.

Put a nail in the wall, paint 'Antique' above it, & hang all your cork/rubber gaskets on the nail....

To use silicon effectively: thoroughly remove all old gaskets, use knife if needed. Clean surfaces with petrol, final wipe down with lacquer thinners. Do not over tighten, silicon will get into the threads & acts as thread sealer.
I don't bother with expensive silicon, just use the cheap Parfix neutral cure from Bunnings.

Being doing it this way since 1978. Or was it 1979.....
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Old 05-02-2018, 06:53 PM
Intruder Intruder is offline
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I would check the things Jay has mentioned and also check the selector shaft seal, have done a few of these in my time. Another thing you could do is add a sealant to the gasket. Good luck with the fix.
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Old 05-02-2018, 07:46 PM
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gke60 gke60 is offline
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i would check that the pan is straight . i had one it was warped from the start,
this is one of the new features of aftermarket parts. lol
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Old 05-02-2018, 10:40 PM
70Chev 70Chev is offline
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Thanks for the replies guys. Iíll check those things out and let you know how I go.
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Old 06-02-2018, 04:55 PM
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bonnevista bonnevista is offline
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A little out of left field...

As this is an alloy pan, I'm assuming that the mating flange is reasonably thick. If this is the case, to ensure that it's actually flat, take it to a machine shop an get it surface ground. It will take them literally a minute (or so) to do it.

If all else fails, Geoff's idea of silicone will work. The only problem I've observed is that car guys with silicone are like body builders with steroids. If a little bit is good - a lot will be better...
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Old 06-02-2018, 05:18 PM
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Use a rubber or cork gasket without sealant, if there is still a leak you have other issues.
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Old 06-02-2018, 07:29 PM
Geoff 4 Geoff 4 is offline
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Darren,

There are numerous places for leaks to occur. Gear selector shaft, dipstick tube housing, k/down cable, speedo housing, etc.

Sounds like you are pretty sure it is the oil pan or mounting. Check the pan for porosity, fill it with kero or metho [ don't drink the metho afterwards...].

If no leaks, back to square one....

You correctly snugged the bolts, the right thing to do. Problem is snugged is not tight, but you cannot over tighten with cork/rubber because you squeeze the gasket out...& cause a leak. The other problem with snugged, not being tight, is that it can loosen...& does. If the pan is ok & you are sure it is the gasket not sealing, use silicon with no gasket, as I suggested & it will NEVER leak. Run the silicon around the inside of the bolt holes, close to the holes to make sure it seals with the case. Apply the silicon the case & make sure the pan covers that area. To make it easier, buy a length of 5/16" Whitworth or UNC rod threaded rod from Bunnings. Cut two lengths about 3" long. Thread each one a few turns into the case, diagonally from each other. Do this first, apply the silicon last as it goes off in 10-15 min, so have all the tools ready. Use the rods to guide the pan into place & not get silicon everywhere.
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Old 06-02-2018, 09:58 PM
70Chev 70Chev is offline
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Thanks again guys for the advice. Iíll pull it out tomorrow night and take it from there.

Geoff, thanks for going the extra mile with the advice. I appreciate it.

Darren
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