I have a 1965 green dot C4 in an off topic 1965 car. It leaks significantly, but only while it’s parked. I have already replaced the bushing, seal and tail housing gasket. It seems like I can get the car out after sitting parked and it will have leaked a good 1/2 qt or more while sitting I will top it off and I can drive it for hours and it won’t leak much if any while driving it, but after it’s been parked for a few hours it will start leaking. I haven’t been able to get it up in the air to clean it all off and try to look to see where it’scoming from, but my theory is that after it’s been parked the fluid must start to drain back down to the pan and then the level rises above the pan gasket and then it leaks from either the dip stick tube or shifter shaft seal or maybe even the pan gasket itself. It doesn’t seem to be leaking anywhere near the front seal area it seems to be back to the middle of the pan or back father. I don’t have much experience with these C4’s is this a common issue they are known to have? The trans seems to operate fine otherwise.. I guess I’m hoping there’s an easy fix instead of what I’m thinking I’m gonna be doing to fix it. The car sat for several years prior to me buying it and getting it roadworthy again.
I think you have a good concept of the problem. The most common fix is a pan gasket since people look at the pan rail and see a lot of fluid (doesn't fix the problem in most cases). However, you need to see if there is any fluid on the case above the pan rail. That means the culprit is either the dipstick tube or the selector shaft seal. I believe that's what you will find to be the source of the leak.
I had the exact same problem with a C4. The trans guy I asked about it also told me it was dried out seals letting the torque converter drain into the pan, overfill and run out of my vent tube..
The level in the pan will always rise when parked. The converter does partially drain down and that raises the fluid level and leaks show up. Most often it's the selector shaft seal and kickdown shaft o ring. Both require valve body removal to replace...not a difficult job but messy.
I’ve always had them leak from shift / Kick down shaft that passes through trans case. Should a seal and an o-ring. Not a 1/2 quart leaking though.
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