Originally Posted by KILLERME
lol ah 5200rpm 161kmh = 100mph
Something doesn't quite add up with those 3.0 diff numbers.
You sure you have a 50 profile on a 205 (23.1" diam)? That's quite a low diameter tyre. Normally they'd have around 60-65% profile making it a 24.5-25.5" diam.
Your 2.75 diff #'s work out OK, 2400rpm @ 100km/h with a 205/50x15, so my bet is that your other diff is lower than 3.0.
3.0 diff @ 5200 with 23.1" tyre = 190km/h (119mph)
To make it work (ie: 5200rpm = 160km/h) you'd need around a 3.5 diff ratio. A 3.0 would have you pulling 4400rpm across the line.
With the diff jacked up you can measure the driveshaft rotations (3) to make the rear wheels spin around once. Or divide the crown teeth # by the pinion teeth # if it's out of the car.