th 400 leaking

[montefreak]

Well i am finally at the end of my rope...I have searched the web and the threads on here and ive tried everything they have suggested....and it still leaks..Ive blown out the vent tube...blown air back through the fill tube...all clear...ive put a moroso gasket on...replaced the brand new modulator...kept the fluid level down some...and it still is leaking.....doesnt leak at idle...it starts to leak after you have driven for a few miles....only leaks from the passenger side also....please someone help me......

[Mister-B]

Originally Posted by montefreak

Well i am finally at the end of my rope...I have searched the web and the threads on here and ive tried everything they have suggested....and it still leaks..Ive blown out the vent tube...blown air back through the fill tube...all clear...ive put a moroso gasket on...replaced the brand new modulator...kept the fluid level down some...and it still is leaking.....doesnt leak at idle...it starts to leak after you have driven for a few miles....only leaks from the passenger side also....please someone help me......

Try a bottle of this. Worked well for me:


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[montefreak]

Im willing to try anything at this point...Thank you for the tip...i will post how it works out...

[Mister-B]

Originally Posted by montefreak

Im willing to try anything at this point...Thank you for the tip...i will post how it works out...

No problem. I have a th400, and this took care of the leak I had
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[Lee H]

Have you determined where it is leaking from? The passengers side has several spots it could be coming from.
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[Tx Firefighter]

I would suggest pinpointing the leak and repairing with new seal, o ring, or whatever it takes. Adding special fluids is a bit of a band-aid.

Get it very clean and spot where the leak is coming from.
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[montefreak]

Well over the weekend i have eliminated two possible exit wounds here...it is not the breather tube and its not the fill tube.....

[chevy88]

Don't forget the kickdown cable entry point on passenger side.

[FLEET72]

Originally Posted by chevy88

Don't forget the kickdown cable entry point on passenger side.

TH400 is electric, no cable.

[motorcritter]

All the transmissions I've seen that Lucas was run in them, had, upon tear down, a fine 'patina' of what appeared to be surface corrosion. It was very light, but present throughout. It would seem that the 'slip elimination' is due to roughing up the surfaces of the metal plates, possibly at the expense of bearings and hard parts. We got to look at the guts when the transmission finally stopped transmitting, as the 'magic sauce' cure is a temporary one, at best. As mentioned above, fixing the leak is preferable to 'magic sauce'. Clean it off really good, and check it closely for signs of seepage.
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[Mister-B]

Originally Posted by motorcritter

All the transmissions I've seen that Lucas was run in them, had, upon tear down, a fine 'patina' of what appeared to be surface corrosion. It was very light, but present throughout. It would seem that the 'slip elimination' is due to roughing up the surfaces of the metal plates, possibly at the expense of bearings and hard parts. We got to look at the guts when the transmission finally stopped transmitting, as the 'magic sauce' cure is a temporary one, at best. As mentioned above, fixing the leak is preferable to 'magic sauce'. Clean it off really good, and check it closely for signs of seepage.
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I don't understand how this product could be roughing up the plates? It doesn't contain any solvents, and doesn't appear to have any abrasives in it. If anything, it should have the opposite effect. I'm not doubting what you're saying you saw when you tore down those trannys, but it could be that those trannys already had major problems from something else, hense why they used the Lucas additive. If your tranny is fine, other than a leak you can't track down, I see no problem in using it.
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[motorcritter]

Whether or not the Lucas accelerated the transmissions' internal failure is always subject to discussion and conjecture. I saw plenty of units that didn't run Lucas, that blew up anyway (usually Mopar, but I digress). I know there are many solvents and chemicals that can react with ATF and any soft parts internally, and that could be the source of the 'patina', no one at Lucas would ever give a straight answer. That being said, the Lucas treatment may gain some time before more severe conditions occur. Leaks, though, are best fixed properly, even when it is a PITA- the 'magic sauce' trick can let go, and the consequence of fluid loss will definitely be more expensive than a leak repair. Clean it up, find the leak, fix the leak- that prevents any uncertainty about what's really going on with the transmission. Pan gaskets are a usual culprit, clean the surfaces nice and dry, don't use any sealer on the gasket and snug the bolts down evenly, but not 'superman tight'. There's an outside chance of porosity or cracking, but that's usually easy to spot. Anymore, whenever I drop a transmission, I reseal it as a matter of course, checking the converter snout and output bushing for wear, too. I only want to do it once!
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[Tx Firefighter]

Originally Posted by motorcritter

Whether or not the Lucas accelerated the transmissions' internal failure is always subject to discussion and conjecture. I saw plenty of units that didn't run Lucas, that blew up anyway (usually Mopar, but I digress). I know there are many solvents and chemicals that can react with ATF and any soft parts internally, and that could be the source of the 'patina', no one at Lucas would ever give a straight answer. That being said, the Lucas treatment may gain some time before more severe conditions occur. Leaks, though, are best fixed properly, even when it is a PITA- the 'magic sauce' trick can let go, and the consequence of fluid loss will definitely be more expensive than a leak repair. Clean it up, find the leak, fix the leak- that prevents any uncertainty about what's really going on with the transmission. Pan gaskets are a usual culprit, clean the surfaces nice and dry, don't use any sealer on the gasket and snug the bolts down evenly, but not 'superman tight'. There's an outside chance of porosity or cracking, but that's usually easy to spot. Anymore, whenever I drop a transmission, I reseal it as a matter of course, checking the converter snout and output bushing for wear, too. I only want to do it once!
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I'm with you brother. If that trans gives me any reason whatsoever, I reseal the entire thing. It doesn't hardly cost a thing. I did a turbo 350 a couple of weeks ago. Without the shift kit, the entire mess was like 25 dollars for parts.












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[montefreak]

Tell me if im wrong...but it seems as though werever the leak is it is under pressure...cause it doesnt leak if i just let it sit there and idle...like i said earlier...it will start to leak after a few miles from the house...i would think that if it was the gasket it would leak at idle also.....so maybe it is the cooling lines only leaking after the fluid is nice and warm do they leak....ive cleaned it off many times so i could check were the leak would be...i get under it and all i see is fluid all over the passenger side....also...my kickdown switch is on the drivers side....

i didnt put the lucas treatment in yet...i bought it...i do want to find were the leak is first....also...thank you all for your continued help...as always you guys are great...

[montefreak]

Is the pan fluid under pressure??? i was told no....

[montefreak]

Well fellows im glad to report that we have found our elusive tranny problem...took the truck out for a ride the other day after changing the cooling lines..thinking they were the culprit...so when i came back home looked under and saw that i had over torqued a bolt and put a crack in my aluminum pan....yikes..
So i found a metal pan to replace the old one and before i put the new one on i noticed the bottom of the fill tube....ah hah...bottom line is i was way overfilling the trans to make it full according to the dipstick....the full on the dipstick is maybe 2 1/2 inches up into the dipstick.....so problem solved...thanks gentlemen....