Transmission hard shifting from first to second

I have a 2500. It has been shifting hard from first to second. My husband (he's been a mechanic for about five years but does not have much experience on older cars) believes that the shift solenoid could be the culprit. (Funny thing is that it shifts much smoothly when its pulling a load) I was wondering if there was any open recalls on my transmission from that year. I have a 4L80E transmission. Any information or advice would be greatly appreciated thanks.