Q: Whats the cause of a whining tramsmission, blinking overdrive light, hesistant to shift properly?

As a rule, I NEVER change the transmission fluid on a vehicle with that high of a mileage unless it has replaced regularly throughout the life of the vehicle. Replacing fluid that is thick with new fluid can cause issues everywhere in the trans.

While performing this service, are you sure you replaced the seal to the trans filter and it seated properly without tearing the seal? If the filter did not seat properly it could cause your issue.

Did you fill it with the +F fluid? Is the fluid level correct while running? Fluid level is everything on a trans.

If all of the above is correct, I think either your have some ’funk’ floating around in your trans getting in some of your valve body jamming up some solenoids or the thinner viscosity of the new fluid is not creating the pressure you need due to worn components.

At 217k miles, you may try a flush service or you may need a new transmission. The whining noise is probably the torque converter slipping a bit due to the new fluid (which requires removal of the transmission anyways). If you would like to have a transmission fluid service done, a certified mechanic from YourMechanic can come to your home or office to perform this task for you.