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My 1990 Oldsmobile Cutlas Station Wagon has been leaking transmission fluid for the past few months. I regularly check it and add fluid when required. (something compatible with DEXTRON II) I was wondering if it is safe to use the product I saw at Walmart that is suppose to stop leaks? Apparently, it should be added to the transmission fluid.

I assume you’ve checked all the hoses, fittings and other easy to fix sources of leaks, and now you’re down to the seals / case leaks that require transmission removal to fix? If not, it might be worth taking your car to the self-serve car wash and really cleaning the engine bay and transmission - top and underneath (be sure the place has a trap for oil and grease to not pollute ground water). Then, take a can of aerosol athletes foot powder (from your same Wal-Mart) and spray it all over the transmission, hoses and fittings. That stuff is glacier white and will stick to everything. Drive your can for awhile and you’ll immediately find the source of the leak, as that cherry-red Dextron oozes out. If its fairly easy to fix (axle shaft seal or more likely the pan) go ahead and fix it right. If it’s the input shaft seal (tranny pull to fix) buy a bunch of Dextron III and leak stop at Wal Mart and keep driving. Those types of products normally work by causing engine or transmission seals to swell, thereby reducing --but probably not eliminating–leaks. The car is almost 20 years old, so you really don’t have much to lose in trying it. Might help reduce the leaking.

Thank you, Sean. I don’t have the slightest bit of expertise when it comes to the car engine. The car only had one mechanic for 16 years and I haven’t found a descent mechanic here - the last one over-filled the oil when he changed it - I’ll have to consult the manual before cleaning the transmission.
I’m pretty sure the temperature change from the extreme cold of NH to the heat of FL summers contributed to the drying out of some of the parts. (even the rubber seal around the windows is drying out.) I think I’ll try your aerosol suggestion. Then, I’ll take it from there.

If you plan on keeping the vehicle and fixing the transmission DO NOT use any kind of stop leaks. This stuff just gets into the cooler and throughout the system and requires lots of flushing to get it out. There are few places where a transmission will leak from. Gaskets and seals… Take the time and replace them. There’s always a downfall to those quick fixes in a can.


Based on that new knowledge, I’ll eliminate the quick fix and search for the leak only. Because this process seems like it may require a good amount of time, I’ll just keep adding transmission fluid as needed. (Do you think that will cause a problem?)
I really appreciate this new information transman.