Speedo reading after gear change without tune question??

Anyone have the link to that chart that shows what speed your speedo will say after you install certain gears but retain the stock tune? My buddy is installing 3.42's in his stock 2.73 rear but won't get around to getting a tune for about a month or two when he gets a couple other installs done and he can kill a few birds with one stone on the mail order tune. He just wants to know what his speedo will say so he doesn't go around speeding all the time. Thanks in advance.

Can't help with 3.42's, but when I did 2.73' to 3.73's before recal, it was about 10mph over. I had a friend trail next to me and that's what he told me. 3.42's, I imagine 5-6 mph over??

the best way to do this is with a gps they all have speedometers on them and it wil tell you right to the tenth how far off you are and being from big rapids i'm sure your familar with a gps.

www.f-body.org/gears/