When your Transmission Fluid is dark it is usually a sign that your transmission is on it's way out. Normally your transmission fluid is bright red. When it is dark it means it is burnt. That would be from running hot. Clutches slipping. etc. I would suggest running it until she stops because I changed fluids that were burnt and all the sludge in it from the clutch packs is what kept it working. Change the fluid and it may be the last time it moves under it's own power. It may also depend on how many miles you have on it. If it has a gazillion miles on it I would definitely leave it alone. If you change it there is always a risk that you should have left it alone.
Souperbee
You don't. These newer 4Runners do not require you to change the transmission fluid and if you need to at all it would only be because of leakage (bad seals) or overheating the transmission with heavy loads.
The Good: Transmission fluid comes out of the bottle dark red, to a lighter red like pink. Could be nothing. The Bad: Water got into your transmission and has produced a milky pink, like strawberry milkshake.
If it is a very dark color with an offensive smell it needs changing. If it smells burnt then the transmission have overheated at some time or another.
the cooling tank in the radiator for the transmission is bad
yes
Bad seal? Bad cooling line to radiator?
too much fluidit seems you may have added to much transmission fluid to the transmission there is a certain amount of fluid all cars require AnswerIF IT IS LEAKING WHERE THE DIPSTICK TUBE FITS IN THE TRANNY HOUSING IT IS MORE THAN LIKELY A BAD O RING
Your trans is either low on fluid,(difficult to check when not a tech) or trans failure. if you check the fluid and it is dark and smells bad and/or metal flakes are in the fluid..... stick a fork in it.
Transmission modulator valve is bad.
check transmission fluid level bad transmission?
Weak transmission fluid pressure. The fluid goes bad after many miles of use. Have the transmission fluid and filter replaced (about $100) immediately before the transmission goes bad. A transmission for that car cost more than the car is worth.
Is this a stick shift or autotrans? yes for now - Check the transmison fluid level - refill if low and change the transmission filter and fluid. Still bad ? People who don't change auto trans filters and fluid at recommended mileages will learn th hard way - maybe.