If the transmission would not go into gear before changing the Transmission Fluid, then the fluid change was for naught. Hopefully you changed the filter in there, too.
If the tranny was busted before the oil change, then simply changing the oil is not going to fix the problem.
You may have a broken transmission or be low on transmission fluid.
Check transmission fluid level (auto) Change transmission fluid and filter (auto)
Try changing the transmission fluid and filter
your transmission is probably going or has gone, check for tranmission fluid leaks because there might not be enough fluid going to the transmission sensors.
Check your transmission fluid levels first
Automatic transmission fluid level has to be maintaned for proper operation, check the level with the dipstick, it is marked to show low or full
The most common reason for a transmission not to shift properly is low transmission fluid. Make sure the transmission fluid is up to the full mark.
Are you asking the cause of the leak or cause of the not moving problem. If your fluid is low that may be the problem right there. YOU CAN BURN OUT A TRANSMISSION BY NOT KEEPING FLUID FULL!!!
THere is no dipstick on a 2005-2007 Mustang since Ford considereds the transmission sealed it wont need fluid added unless it has a leak or you are changing the fluid.
try changing the filter and the trans fluid
If the transmission won't shift out of first gear on a 1992 Buick Roadmaster, it could indicate the transmission gears are seized. It can also indicate a low fluid level.
the car wont move when you put it into gear no matter how hard you hit the gas. you hear alot of clicking and grinding when you try putting it into gear, it wont go above a certain speed {usually indicated a specific gear broken}. try changing the fluid and screen in the pan. 3 years auto mechanic and graduate of apex technical school.