Hello. I bought a 2000 sr5 4runner with 160,000 miles 3 months ago. Its got no mechanical issues except for a tiny leak in the valve cover gasket that the shop thought wasn't an immediate concern. This is my first car. I decided to change the oil and ended up draining the transmission fluid instead. I looked under the car and thought the transmission fluid pan drain bolt was the oil drain bolt. The drain bolt said DII. It was all dirty so I thought it said OIL. Anyway, I drained it (~5 qts came out) and then poured 5.5 quarts of 5w30 into the oil reservoir. I then checked all my fluid levels. The oil was at the correct level (how? I added 5.5 qts and didn't drain it) and the transmission fluid was low (duh). I then drove about 3 miles, looked up how to change transmission fluid and realized my mistakes.

Anyway- these are my questions. Did driving missing 5 qts of ATF hurt my car? What is the appropriate way to fix this? Can I just pour 5 qts of fresh ATF back in or do I need to take it to a shop? Also, my oil level was correct before I changed the oil. How did adding 5.5qts of oil not overflow something since I didn't actually drain the oil.

Thanks- as you can tell I don't know what I'm doing

 

Welcome to the forums and to one of the best little trucks ever, imo. Learn lots via great forum support and even how-to videos to help you navigate owning an older awesome vehicle.
Which did you get, the 6 cylinder 3.4 liter or the 4 cylinder 2.7?
Is it 4wd? That would give you 4 potential drain plugs.
Pics of what you did where might be useful...best bet is to not drive it until this gets sorted out.

What does your oil dipstick say? By oil reservoir you mean the hole in the valve cover for oil? There are 3 actual reservoirs and none are for oil.
What does your transmission dipstick say?

 

As Hab said, it would be really helpful if you had a picture of which drain you opened. Also the fluid you drained out, do you remember what color it was?

(Assuming a 4wd) The front differential has a drain bolt on the side, it isn’t easy to get to and I doubt you would mistakenly drain from there. But if you did, the front diff hold gear line which is thick like honey and maybe about 1.5 qts would come out.

next is the oil pan. This would have a drain plug that just screams “easy access”. Here motor oil would drain out, somewhere around 5 qts and it would be basically black or really dark brown if it has 3-5k miles on it. (Unless it synthetic which holds its dark amber color longer)

Next is your transmission pan, my ‘99 doesn’t have a drain bolt. To drain mine you have to either drop the pan or split the cooler line running to the radiator. If yours does have a drain bolt, the pan itself is a big flat aluminum pan about the size of a roasting pan, and it would drain a maroon fluid. Draining 5 qts isn’t the end of the world, the system holds like 17qts with a full torque converter.

Next is your transfer case. Again this holds gear lube, the drain bolt isn’t as apparent as the oil pan. This should drain around 3 qts.

Lastly is the rear differential. This is the center of the rear axle. It has a big drain bolt on the bottom. It should drain around 2 qts of thick gear oil.

please post some picks and we’ll help you sort it all out.

 

This is the Transmission fluid pan right ? This is what I drained.

 

Yes. Now where did you pour in the 5 quarts of new engine oil? You called it a 'reservoir'. Post up a pic of that.

 

Ha, I didn't mention that one 'cause I figured even the transfer case would be a bit of a stretch. It is a good thing to mention, especially for someone trying to gain experience.

@Bridger McKinney We'd love to help you figure this out. Not everything goes as planned every time for any of us, it happens.
It sounds like you got a nice (congrats on the low miles!) truck.