Confirm Trans Problem on 2000 Blazer

Read several postings on this forum about issues similar to mine. Would like to confirm what might be wrong with my tranny. Was working fine and shifting flawlessly until today.
Now there is no reverse---just a faint whine
Revs up and shifts from 1st to 3rd, with no 2nd gear
Converter still locks up about 47mph
Does not shift into 4th gear----at least not up to 65mph
Also noticed no engine braking. Foot off the gas at any speed, and the tach goes down to 700rpms
No Check Engine Codes

Is this a simple solenoid replacement, or is it the dreaded Sun Shell or whatever?? Any and all advice would be appreciated

Sounds like you've done your homework by reading the other posts. I had a 99 Blazer with the identical symptoms at 158,000 miles. It was the sunshell, and it had to be rebuilt. I actually bought a rebuilt one (trade in). My Blazer had a 4L60E in it I believe. Another family member had a Jimmy with the same problem at 127,000 miles. It's pretty common.....