After runnin at speeds above 55 for about 10 minutes the check engine light comes on. Ran the codes, got a 621, shift solenoid number 1. Got an E40D with about 2 years and 22K miles on a full rebuild with the Banks trans-command module too. Any ideas what to look for before i start throwing $300 solenoids at it?

Anyone have any ideas?

check the electrical connection at or near the trans for corrosion. You may have to pull the pan and check the wiring there also for any damage. If not, have a trans shop check it out, most usually have a basic diagnostic charge and they should be able to tell you what's wrong.