I changed my 4L60E transd for a 4L80E and did the wire conversions, but now when I get up to 6mph my truck Cuts out and dies. What could the problem be?

Welcome Was the 4L80E segment file added to your existing tune?

you have to change the transmisson perameters in the tune.

Is there anyone here that can do this for me? And what would it cost?

There are several sponsers that can recalibrate your ECU for the swap.

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In no particular order

Black bear
PCMcalibrators
Wheatly
Klug Performance
Nelson performance

there may be other sponser that I am not aware of that also offer that service.

...or wire in a relay.

I'm going to make some calls to them tomorrow. Thanks. I read about the relay, but I did not understand it too well. I'd be better off leaving it to the pros.