nailing down Transaxle code P0742

I have a high mileage (252K) '97 SSEI with the 4T65E-HD transaxle. The car has been used exclusively for long business trips. The transaxle shifts smoothly and normally, but misses 3rd; it shifts 1-2-4-4OD, code P0742 - TCC fault. Sometimes, especially when cold, under very light acceleration, around 35mph, I notice a slight 100-150 RPM drop, so the signal to shift is obviously good and the car is attempting to do so. Considering the high miles, though, the only response I have had from a shop is to fully rebuild it. I've been told the transaxle fluid looks good and the transaxle shows all signs it would be fully rebuildable. But still I'm wondering what actually is the problem and whether it is really necessary to pull it all apart to fix it. Do you think this is in the valve body and might be fixable w/o pulling the unit out of the car? Thanks in advance for your reply!!

if you have 1-2 and 4th, then both of the shift solenoids are working..

I think you possibly are seeing 1st, 2nd, 3rd then TCC Lock in 3rd, Reason I say this is that its common for the 4th Input hub shaft to strip out... with the miles you have on the trans it is time for a rebuild.. Highway or not thats a lot of miles for a 4T65-E or any trans for that matter..

are you 100% that it skips third gear? It is also possible to be having a 3rd apply problem cause buy a Lip seal iirc...

All I can see for your future is a used low mile unit or a full rebuild..