The ideal RPM range depends on your engine, and the speed depends on your transmission gear ratios, rear end gear ratio, and tire revolutions per mile.
It's the same as the shift pattern for the Eaton Fuller nine speed transmissions, albeit with additional gears on the low side. For the sake of not wanting to type out a long winded explanation, there is a related link posted - 'Eaton Fuller 18 speed shifting diagram'. Click on that link to see a visual representation of the shift pattern.
As many as the purchasing agent ordered it with. It could have an Allison automatic with five or six gears, it could have an Eaton-Fuller manual or automatic with 9, 10, 13, or 18 gears, it could have a ZF Meritor automatic with 12 gears.
No. Unless you have a "C" transmissions (e.g., RTOC, RTLOC, etc.), it's not convertible. A 10C transmission doesn't convert to a 13 speed - a 9C transmission does. A 10C converts to a 15 speed, which remains essentially a 10 speed with five deep reduction gears.
Depends on what you have. If you have a Volvo outside of North America, it has a synchromesh transmission. Volvo synchromesh transmissions are extremely rare in North America, and they'll more often have Eaton-Fuller twin countershift unsynchronized transmissions, where you have to manually make up for the lack of a synchronizer gear.
Transmission gears? In the transmission.
On an unsynchronized manual transmission, you either have to double clutch (which will be required on any road test or "float" the gears. For the actual shifting patterns, diagrams should be readily available online.
Can it be done? Yes. Should it be done? Absolutely not. The manual transmissions available for the F750 from Eaton Fuller and Spicer were synchromesh transmissions - nothing like the unsynchronized twin countershaft transmissions found in Class 8 trucks. Trying to float this box could destroy the synchronizers and ultimately cause the transmission to have to be rebuilt or replaced.
Gears is what transmission is for. No gears. No transmission!
A c-4 transmission has 3 gears.
When your RPMs get down to 1000, you take it out of gear, press the accelerator to tach the motor up to 1500 RPMs, and drop down into the next lowest gear. Assuming you're operating this truck in North America, your transmission will either be an Eaton-Fuller or Spicer 10 speed unsynchronised transmission, and you must tach up to motor to compensate for the lack of a synchroniser gear in the transmission. If you drop your RPMs down to 700 - 800 before downshifting, you can skip a gear in downshifting, and downshift two gears.
3 gears
The transmission allows you to shift gears.