i just put another rear end in <complete> did wheel turn to ck. gear size<3.73 was told> . but when in over drive it reads 42-43- mph at 1500rpms tires 27.74 tall. i think might be 4.10. what do you think

 

Assuming you are refeing to an A4 overdrive then yeah is sounds like maybe 4.10's but how are you measuring these? are they with the factory gages? was the computer programmed for those tires and the 3.73's? All these things effect the results and/or could be misleading...

I suggest you just test it but by the tire/d-shaft rotation method to see exactly what you have...