Chevrolet Repair: Chevy conversion van trans shifts hard, chevy conversion van, lazy release

Question
I have 1997 Chevy conversion van with approximately 67k original miles on it.  Recently the transmission has started to shift hard from first to second, but only have the motor has been warmed up for quite some time (highway driving will always cause this but driving 10 miles to the store will not).  I did accidently run over a high median, so I'm not sure if something got knocked loose at that time.  I checked the trans fluid and it's level is correct and does not smell or look burnt.  Also the motor does not run excessively hot when the problem occurs.

Answer
Hi Steve,

Transmissions take longer to heat up than motors.  Sometimes a good 10 or 20 minutes of hard driving.  

Did this happen when the median was hit or prior?  Is the pan dented?  How hard was the hit?  A van should take a little abuse from a median.  

Could be the fluid is too thin/weak after heat up.  Could be internal leak by at a seal, or a lazy release of a band or clutch from gunk.  

I would take the van in for a check-up and a fluid transfusion.  This could be $50.  

C J S