94 escort gt trans question

I have a 94 escort GT with an automatic trans and a 1.8 4cylinder.
It shifts fine from 1st to second but when it goes from 3rd to 4th there is this high reving sound like it doesnt want to shift, then it finally shifts
into 4th.
when I am stopped and put it in park, I can hear a low humming that goes to a high pitch then stops.
Could thisbe electrical or is it the trans telling me it's tired?
Fluid is full but has a reddish dark color but no odor
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smantas opined in

1. Does it do this hot or cold?
2. Have a full trans flush or do it yourself by draining out the cooling lines while idling..change filter..refill carefully watching stick every quart after 4; then add a bottle of Lucas AT additive.
Cant hurt
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