99 gmc jimmy tranny leak?

Where's the leak coming from? On that truck, it is VERY common for the transmission cooling lines to leak at the transmission. But, whatever you do, DO NOT use that stop leak. Fix it right.

WARNING!!!! DO NOT AD STOP LEAK!!!!

It just swells the seal and in a few months you will be leaking fluid like nuts!!if its a small leak its probably ok for a while but not good for the environment. Have it look ed and se where the leak is. Rear seal or pan gasket is an easy fix. Front pump seal means the tranny comes out $$$ so you make the choice. Good luck.

You are not screwed. The fact that the tranny will shift manually is proof of that. You simply neglected one thing before you flushed the fluid. You should have added a good quality pre-flush cleaner and let it circulate about 15 minutes before the flush. I prefer BG Quick Clean for Automatic Transmissions but almost any premium brand of transmission pre-flush cleaner will do the job. You now have 2 options... do it again the right way or pull the valve body assembly and give it a thorough internal cleaning with parts cleaner. It's a very simple task but if you don't trust yourself with the disassembly and re-assembly of the valve body then just remove the valve body and take it to a tranny repair shop and ask them to clean it for you. I have flushed many high mileage automatic transmissions and I would bet the ranch that many of them have never been serviced. But contrary to what some people say about transmission problems after doing that, I have never, not even once, had a transmission return with problems caused by the flush. But at the shop I worked at pre-flush cleaning was routine. And in addition to that, if there was any visible traces of gum, varnish, sludge, or hardened deposits when changing the filter after the pre-flush cleaning, it was routine to recommend removal of the valve body for a thorough internal cleaning and inspection. So as I said above, you have 2 options now. Do the flush again the right way, using a good quality pre-flush cleaner and let it circulate for about 15 minutes before the flush or pull the valve body assembly and give it a thorough internal cleaning with parts cleaner. Good luck restoring smooth "automatic" shifts to your tranny.

Its always best to do it the right way the first time. Getting the gasket would be the best thing to do. You can try the quick fix fluids but I would only do it for short term fix. Every1 has there own thoughts on the quick fix fluids. Just my 2 cents

fix in a can never works, you need to either replace the gasket yourself, take it in, or keep adding more fluid

i own a repair shop,and i don't think that stuff is a good idea for a good working transmission,i have had to re-do a lot of transmissions that have had that added to them,it stops the converter lock up switch up on them,and also cause slow sifts in a good transmission also,and on some occasions it has actually stopped a few leaks,but i have to warn you it may cost you a transmission in the long run,i have seen it happen a lot ,its good for my business that they sell it though,this way i always have work to do,but im not kidding you it will cause more problems than it will do good,i hope this help,s,,good luck.

additive will do no harm but more than likely won't fix the problem if it needs a seal or gasket.