TH400 leak

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B1075

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Brandon
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1977
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C10 Scottsdale
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350
Hello all, I have a 77 Chevy Scottsdale that has been sitting in a garage for about 10-11 years it has been in the family since new. It has just over 100k original miles. I have gone through and tuned everything up. The truck runs great but I haven't taken it on the road yet. It sat for a couple weeks and I noticed it had about a 4'' puddle of transmission fluid under it. I started it and moved it, ran it for about 15 minuets at idle and another puddle of transmission fluid was under it. I know its old and its going to leak some fluids but is this a huge problem or something that might not be an issue if I keep an eye on the fluid level? the fluid seems to be coming out of the weep hole in the cover between the motor and transmission. Thank for the help.
 

Bextreme04

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Hello all, I have a 77 Chevy Scottsdale that has been sitting in a garage for about 10-11 years it has been in the family since new. It has just over 100k original miles. I have gone through and tuned everything up. The truck runs great but I haven't taken it on the road yet. It sat for a couple weeks and I noticed it had about a 4'' puddle of transmission fluid under it. I started it and moved it, ran it for about 15 minuets at idle and another puddle of transmission fluid was under it. I know its old and its going to leak some fluids but is this a huge problem or something that might not be an issue if I keep an eye on the fluid level? the fluid seems to be coming out of the weep hole in the cover between the motor and transmission. Thank for the help.

It could be a problem. It depends on where its actually leaking from and why. There's a few things in there that could be causing it, but that's not a trivial amount of fluid and one of the primary causes of burnt up transmissions is low fluid level.
 

Matt69olds

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If it’s coming out of the torque converter inspection cover, and only while running, it’s most likely the converter seal, or coving from the pump o-ring or gasket.

Either will require transmission removal to fix. The converter seal can be changed without transmission disassembly, before driving in the new seal make sure the bushing hasn’t started to walk out of the pump. If the bushing is coming out of the pump, the transmission is going to need some exploratory surgery to find out why.

If the pump is dry BELOW the input shaft/torque converter support, then it’s most likely leaking around the pump. This is where the laws of Might as Well (MAW) can kick in. Depending on mileage and condition, it might be best to just have it rebuilt. It’s a big hassle removing a transmission to fix 50 bucks worth of gaskets and seals to have it fail 100 miles later.
 

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