uno

I have a 95 2500 4x4 5.7lt 4l60e. I replaced the trany less then 800 miles a go and now when I put in drive it feels like im pulling a house down.And the tack and gear selecter on the dash wount lite up but when they are working the trany works for a while any info would help alot thanks p.s. reverse is strong and trouble codes are 66,67,81,82