Can’t find this particular problem in any of the threads. 2005 Chevy Ventura minivan. Transmission “slams Hard”into 2nd gear. No problems shifting into any other gear, just from first into second.. (unless I manually shift the automatic transmission from first into second). If there was a problem with the pressure valve (solenoid) wouldn’t that affect all the gears?

 

I don't think it's a particularly uncommon problem. The 4T65-E transmission, whether in your minivan, or a Buick Century or Pontiac Grand Prix is known for this.

If you have an OBDII tester, see if you can find a trouble code, such as P1811. You didn't say how many miles are on the transmission, but it could simply be that second gear is wearing out. If this is the case, then is will start shifting slower. But the transmission 'brain' sees this as a problem and so puts in full line pressure, causing an abrupt shift. You could live with it, or rebuild the transmission, or for much less cost put in a shift kit (such as https://zzperformance.com/products/4t65e-shift-kit ) which will speed up the shifts so that the computer doesn't react to it.