97 GC. Trans issue from Reverse to Drive

[Roadraider]

3rd post here, 3rd problem with my two GCs I am about to blow up today with these cars!!

Anyway, off all 3 problems this is the least urgent now but still something that needs fixed.

Car is a 97GC SE, 3.8L, 160K miles

For the past 3-4 weeks the Trans has been acting up, well in a way. Our driveway has a bit of an incline and normally the car gets parked with the nose up.

When we drive off, we Reverse to the road, then put it in Drive and on our way. The last 3-4 weeks, trying to go from Reverse to Drive does nothing! I mean, nothing! You can sit there trying time after time but no go.

If you shut the car off and restart it, goes to Drive immediately with no problem. I have not detected any slipping or any issues switching gears while driving. It's only from R to D.

Also, the last week or so, when you go on the brakes a little hard, the Trans gets off gear when the car stops, a sec or two later pops back in gear again and off you go with no other issues.

Took it to a client of mine who has a Trans shop. Left it overnight and he told me that Trans needs to be rebuild. He says Reverse is in bad shape. Do I trust him? Not sure, he is a client but I don't know about their shop reputation.

Hmmm, I know that these Trans go at around 150K miles but are these symptoms and indication of it going bad? Doesn't sound right to me.

Could it be the Shift Solenoid that needs to be replaced?

Any ideas what else it could be or what to check? I would appreciate any help and will report back on what comes of it.

Thanks!