Transmission Gremlins

96 SVX 106k
1. Lately when driving with the transmission in "3", I have noticed that it sometimes is reluctant to upshift from second to third. I will be driving along at constant throttle around 45mph and it stays in 2nd. If I lift up on the throttle it shifts to third.

2. Yesterday morning, I had the lever in "3" and the transmission was in third. I was driving on level ground at constant throttle around 45 - 50 mph and suddenly the rpms jumped (I assume it downshifted into 2nd). It stayed like that for 3 -5 seconds and then apparently shifted back into 3rd. This happened three times on about a 5 mile stretch.

3. Last night (and this morning) when driving with the transmission lever in the "1", "2" or "3" position at constant speed and on level surface, if I lift entirely off the throttle the rpms drop to between 850 - 1250 and the car feels as if I have shifted into neutral. It only gradually slows down - there is no compression braking. I can blip the throttle and take the rpms up to 2500 with no apparent effect, again just like the transmission is in neutral. If I drive with the lever in "D", all seems well. I checked the transmission fluid with the engine and operating temperature, engine running and transmission in "P" and it it about 1/4 inch above the hot full mark. After letting the car sit overnight I checked the fluid level before starting the car and it was about 1 1/2 inch above the hot full level. I would have thought that the level should check lower when cold than hot. Any ideas what is going on here? Any suggestions?

4. I had the duty solonoid C replaced three months ago at 102K and that is the last time transmission fluid would have been added. I had not checked the level since then until yesterday.