transmission question

When my transmission is cold it shifts hard from 1st to 2nd after about 3-5 minutes of driving it will shift fine... is this just because the fluid is cold maybe?

And also is it normal for the torque converter to lock when i have extra weight in the truck? a few weeks back i cramed a 150lb table w/ about 10 lb of folding chairs (yes it was packed full to the brim) + me (130lb) in the back and for the first time since i got the truck about a month ago the torque converter was locking.. usually when i just do my daily driving it just goes into OD and it doesnt lockup

thanks

edit- its a 97 blazer lt 4x4 4dr

How many miles on it?
Has the transmission ever been serviced?
Any check engine light on?
Engine running up to par?
Fluid level and fluid condition?
There is a lot OF TSB's on the harsh 1-2 shift.
But we need to know if any or what no. transmission codes are set in the transmission pcm.

135,000 miles
tranny rebuilt/flushed 15,000 miles ago
no check engine light/codes

How much of the transmission was rebuilt?
New converter or valve body rebuilt?
Did it do it before or right after rebuild?
First step is to get a transmission capable scanner on it and read out transmission codes and data.
Watch the pressure solenoid data and shift delay data in the scanner.

How much of the transmission was rebuilt?
New converter or valve body rebuilt?
Did it do it before or right after rebuild?
First step is to get a transmission capable scanner on it and read out transmission codes and data.
Watch the pressure solenoid data and shift delay data in the scanner.
not sure how much of it was redone, the previous owner had it done and showed us the receipt to prove it, i dont have the reciept anymore so i cant confirm.

it was about 78 degrees today and it shifted like a charm, ill keep an eye on it, but at this point im not going to worry.