HELP...Leaky Ass 350 Trans Pan/Gasket

The leak comes from too much fluid in the pan. The torque convertor is not holding the fluid and is draining back into the pan. The front pump bushing and seal is worn. Replace them and the drain back will stop.

The other fix would be to get a deeper pan but do not add to the amount of fluid. Deep pans come with an extension to lower the pick up tube to the bottom of the pan. Remark the dipstick at the deeper level with no extra fluid. When the torque convertor drains back, the fluid level will be below the pan rail and you will stop your transmission from leaking.

 

Had the same problem, after sitting for a couple weeks the 700-r4 would leak. Figured it was from torque converter drain back. Numerous attempts to fix, finally once more put the car on the lift, cleaned it up and went on vacation for awhile. Came back and she was leaking, traced it back to a approx 1/8 hole in the center of the yoke going into the trans, pulled driveline remove yoke and plug welded hole, polished up and problem is gone

 

Blue RTV is the worst crap ever for everything.

 

Shift shaft seal or pan contorted at the boltholes..350's only leakin the hands of DIYFers.

 

"350's only leakin the hands of DIYFers." What's that mean?

 

Sounds like he works in or runs a tranny shop.

 

Well shit! I would hate for somebody to try and fix something their self...

 

A while back I was going through some old Goodguys mags and pulling the tech articles out and filing them when I found an article by Brent (Fatman) about the problems of trans coolers being mounted higher than the trans pan and the lines draining back into the pan and basically overfilling the trans. just a thought.

 

I've seen some fitting with little check balls in them. And yes, most coolers are above the pan

 

Those shift shaft seal tools are a huge time saver. I've had to borrow them from my Trans guy- he can't remember where he got them so I can't get my own ugggh

 

I was looking for that tool years ago. I finally gave up and used a straight pin to pull the old seal out and a socket to push the new seal in. Worked great and never leaked again.

 

Yep, the fittings in the radiator for mine are 6" above the trans pan gasket surface and I've got about 5 ft each (10" total) of -6 2807 Aeroquip hose full of fluid that can drain back. What Brent did was install a "U bend" loop on the return that went higher than the cooler ports (in the article) then down to the fittings on the trans. Leaks suck! A customer's (OT) '72 C-10 leaked all over the shop floor because he couldn't get the chrome trans pan sealed up. Switched it to a stocker and rubber gasket and it quit. I also changed the O ring on the dipstick tube.

 

Yep, the fittings in the radiator for mine are 6" above the trans pan gasket surface and I've got about 5 ft each (10" total) of -6 2807 Aeroquip hose full of fluid that can drain back. What Brent did was install a "U bend" loop on the return that went higher than the cooler ports (in the article) then down to the fittings on the trans. Leaks suck! A customer's (OT) '72 C-10 leaked all over the shop floor because he couldn't get the chrome trans pan sealed up. Switched it to a stocker and rubber gasket and it quit. I also changed the O ring on the dipstick tube.

 

Blue RTV isn't compatible with anything! It is the worst stuff , every time I see that on a car I cringe.
The best sealant to use on transmission/diff. pans, cases, etc is Toyota seal packing pn. is oo295-01287.
Not cheap but, if installed correctly, it will not leak!

 

A friends T400 did the same, one thing he did was over tighten the pan bolts and cracked the alloy pan, secondly the front pump seal where convertor snout goes in was weeping. Once fixed, no leaks.

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6 months ago pulled the th350 out of my old's ,new filter pan gasket new seals front and rear shifter seal dip stick seal speedometer seal and o ring.drove it a few times before winter .no leaks . this past week started it up no drive no reverse . down 4 quarts .( parked in shed over gravel)
Is it possible that converter leaks down and fluid over whelmed the pan gasket ( drips on pan no where else)?

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Convertors are sealed (Welded) to retain fluid, a friend who rebuilds transmissions advised me that convertors can only be pulled apart for rebuilding/modification only so many times as they need to be welded back together and sealed. Maybe there is some porosity on a weld if it's been rebuilt? My 35 Chevy sits for periods of time when not driven and doesn't leak. Gravity and normal atmospheric pressure will cause fluid to leak out any unsealed nooks and crannies below the fluid surface level.

 

The problem with rebuilding converters several times is that you lose some of the overlap every time you cut one open with a lathe. They do make repair rings, where you can add that material back and double seam it. Most of the time a small pin hole will fix itself. Converters contain the world's best stop leak ( metal, aluminum and clutch debris), under pressure and centrifugal force. I doubt that's the problem here.
The pan and gasket, when applied correctly , should contain and seal the fluid , whether the converter leaks down overnight or not.