This is the 4t65e in a Buick PA. After transmission warms up, when shifting into "Drive" the RPM'* will (sometimes) drop low (500 and lower) and transmission will delay to engage, then jerk into gear. I'm thinking the PCS solenoid (common problem) is causing low line pressure and needs to be replaced. Searching the forum found a few with similar problem, but no resolution.

Fluid level is good, but could use a fluid/filter change. However, since another Buick I have is on its 3rd PCS, may just go that route. Did add some Lubegard Red but problem is still there. Any thoughts on this?

Tough to say what is causing it. Delays going into gear but the RPM drop to 500 and sometimes a little less during the delay into gear, do I have that right?

Thanks Bill...Right, when the delay occurs, the RPM'* drop way low and the car almost dies. The problem is intermittent. When the car goes into "Drive" normally, the rpm'* do dip a little, but the transmission engages and the RPM'* recover quickly.

Thinking the problem may be related to the engine, I had the plugs and wires changed recently. Bought some MAF cleaner but need to do that. The car is a 1999 and has 85k.

I do have the service manual and there is a troubleshooting table for a delayed shift (which is determined as 3 seconds or longer). This delay is not three seconds, but there is a delay. One of the listed causes (in a list of 10 or so) is low transmission line pressure so that is why I'm thinking the ever failing PCS solenoid.

The 97 I have had one replaced at 60k, and another at 140k (car now has 160k, on 3rd upper intake now with a Dorman with a sleeve from Bill Buttermore and smaller stovepipe). I know others who have needed this solenoid replaced as well in the 4t65e.

Looking through the forums, other possible culprits could be: fluid/filter, IAC valve, TPS, O2 sensors, CAT, fuel filter (had this changed), transmission/motor mounts, or the fuel pressure valve.

This car did have a recall on the fuel pressure valve which was completed before I got the car. My scanner does not have this parameter darn. I need to pull the vacuum and check for gas smell. The MAF and O2 readouts look to be in line with the 97.

Was hoping someone had this specific problem and could pinpoint quicker.

You are on the right track. Let us know what you find.

These trannies suffer from a worn boost valve which can set the code 1811 if I recall. I used to replace the PCS and this valve on all 4T65 rebuilds.
From your symptoms, I would not expect this to be your problem. It could be low pressure, but not likely because of the PCS at idle. You should do a line pressure check before you try any repairs.