I am putting an M6 rear with 3.42's in my buddies 99 A4.
IT's got the stock 3.23's now.

Question is does he really need to reprogram for the new gears?

3.42 / 3.23 = 1.06

Since the PCM uses MPH and current tranny gear to determine shift timing & speedo readings.

If we dont reprogram, it looks like it'll raise his shift points by 6%
roughly 360 RPM @ 6000 rpm...

and his speedo will be off by 6% as well..
ie... when he's going 64 (on the gauges) he's really going only 60 MPH in reality...

is this something that needs taken care of ?
Dont most people raise their shift points on the A4's anyways ?

advice please.

 

Only the speedo is going to be off, shift points will be roughly at the same RPM. The drawback is it's gaining odometer mileage faster. Otherwise it's going to be fine.