Gears & Axles - S10 gear help

My friend has been saying his 94 5 speed S10 4 banger has no power.... And of course he seems to be lost to why this is :eyes:. Any way i checked his RPO codes and the truck list his rear diff code as a GT4 (3.73) rear gear, However today i had the truck in the air doing is brakes i marked both the drive shaft and tire and rotated the drive shaft about 2 1/4 times to one full tire rotation :confused:. This made no sense to me so i checked it two more times and each time i spun the drive shaft about 2 1/4 times to one full tire roation. This would mean the axle ratio would be somthing like a 2.23 :confused:

What the hell is going on here guys because i am lost.

Has he put bigger tires on it? A taller tire will effectively make the gear ratio numerically lower.

NO. He is running stock tires. And this is a rotation test so the tire should still turn one time per x amount of given gear.

NO. He is running stock tires. And this is a rotation test so the tire should still turn one time per x amount of given gear.

It's the differential. You need to turn BOTH tires or it's 1/2 the ratio. So, half of 3.73 is 1.865.

Al 95 Z28