89 700r4 problem

Problem started with a hard downshift to first at stop lights then subsided I thought it was the lack of grease in the sliding yoke... two months ago... yesterday the shift point from first to second was a higher RPM than normal. I changed the filter and fluid and no help. Now, all shift points are higher, and first to second is very high. If I accelerate fast, it shifts, but hard and a bit high. If I go slow, it won't shift into second... Is this the death of my tranny or just a valve or spring ? 89 700r4 behind a 350 tbi 229,000 miles on truck ( Blazer Silverado ) Thanks for any help I'm in the middle of nowhere and poor R.