Engine coolant can enter an automatic transmission if your automobile has an integrated radiator and Transmission Fluid cooler, and a leak occurs in same. Many automobiles have integrated radiators / transmission coolers.
Another less likely scenario is that the vehicle was recently flooded or parked in flood waters.
Yes water cause leaking
I can't see any reason for water to get in the transmission unless it went under water from a flood or crossing a stream. If engine coolant is getting into the transmission I would blame the transmission oil cooler in the radiator in which case the radiator would need replacement and the transmission flushed professionally. If the vehicle was driven with coolant mixed in with the transmission fluid you will probably have transmission failure before long.
ofcourse
change the fluid after finding where the water comes from water will cause rust in the transmission if left in
Failed radiator transmission cooler.
if this vehicle is automatic,the most likely cause would be the transmission fluid cooler. it is a tank inside the radiator that cools the transmission fluid. if by any reason the tank leaks it would contaminate your water/coolant/antifreeze. answer a cracked head will allow oil into water jacket in head, going from there thru to radiator if it was a bad head gasket, u would have water in oil instead
blown head gasket....not good. Could b Transmission fluid because the transmission cooler is in the radiator-especially IF the water has a red tint 2 it,IF it has a automatic transmission.
what would transmission not to shift in to overdrive
Replace your transmission pump or get a new transmission.
Leaky transmission lines would cause the fluid level to drop and eventually cause the transmission not to shift and go.
The gears in your transmission may be sticking or worn out. This would cause your transmission to not be able to shift.
Automatic transmission fluid would likely cause a standard transmission to overheat and wear the gears at a high rate.