R & R a 4L60E now no reverse Ideas??

I bought a used 4L60E transmission and was told it was good with 68,000 miles. It looked good on the inside ie. No metal, no brown band dust and I even cut the filter open and it was clean looking inside. I installed it and it has no reverse and stays in first gear until about 3000 RPM and then shifts and RPM drop to 1200 RMP. Could I have did something wrong? Will an adjustment of the shifter help? Can it be fixed with out taking it out? Any help would be kind before I off load this thing to charity.

Its got a broken sun shell. Same thing happened to me this week. If you get it replaced, get "the beast" sun shell.

The "Beast" sunshells do break and I know one transmission shop, Z Transmission in Muskegon,Mi can prove this.They have seen them broken.Call the yard you got the transmission from first,they will work with you most of the time.I agree needs a sunshell.Another thing to while it is apart is to look inside the direct drum,look for 5 outside black springs and there is one thing to do with them: THROW THEM AWAY!!!!The aftermarket says to throw them away and GM says to put them back in.The problem with those springs is that they restrict the clutches from floating and will burn them up.This is what most transmission shops will tell you.

Thanks to all..... I had the trans rebuilt and a rebuilt torque converter installed.