I have engine rpm, vehicle speed, Rear axle ratio, Torque.
The description in the link posted by Vitalii is good, but it assumes that you want the RPM of a drive shaft, in a (rear drive) car where the transmission is not combined with the differential. So it's not really the "propeller shaft RPM" you're getting, depending how you define propeller shaft. In other words, it's not going to be the engine's crank shaft RPM, unless the transmission is in a gear with a 1:1 ratio.
This is a basic physics problem. To start, assume a rear drive car, for simplicity.
If the car is traveling at a given speed, the radius of the wheel-tire assembly will determine how fast the wheel hubs will be spinning.
http://www.softschools.com/formulas/physics/tangential_velocity_formula/25/
Then the differential ratio (so-called "final drive ratio") will determine how fast the drive shaft spins, compared with the wheel hubs. Usually, the drive shaft turns faster than the hubs of the driven wheels.
Now that you have the RPM of the drive shaft, you use the transmission ratios to determine the engine RPM, which is the crankshaft RPM. In the older traditional engines, that will be your propeller RPM. Most cars now have electrically-driven fans.
In front drive cars, the half shafts that connect the transmission to the front wheels will obviously be turning at the same rate as the wheel hubs, and the "drive shaft" will be invisible, usually built into the transaxle. See this:
http://www.carid.com/articles/transaxle-vs-transmission.html
Similarly, in rear drive cars that combine the transmission with the differential, also called transaxle, located where the differential usually is, the drive shaft will be turning at the same speed as the crankshaft, which is determined by the transmission ratio in use at the time.
So, fairly straightforward. You need to be sure to keep your units correct, and you need to know the drivetrain's configuration.
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