This mod adds a few different transmissions to the T-Series truck, that utilize a rangebox to get the desired ratios. Now you can shift this thing without having a 12-speed H-shifter! This is made for sim truckers mostly, who use a shifter with a range paddle on it, however I have a button mapped on my steering wheel to switch between Hi/Lo range.
The range status will automatically start in high, so make sure you switch it to low before driving. This mod works best if you map the range selector to a button or switch, so that you can make seamless gear changes. As of right now, there are three gearboxes available:
10-speed (5-speed with hi/lo)
-the cheapest and most basic, with a tall highway gear12-speed (6-speed with hi/lo)
-offers great highway cruising speeds along with closer spacing for more elevation change14-speed (7-speed with hi/lo)
-very close spacing with very short gears, really only designed with carrying very heavy loads up steep grades in mind.and two rangeboxes available:
-the standard 'box, providing enough oomph in low range, but with long enough low gears for easy maneuverability with minimal shifting4.94
-an optional shorter 'box, sacrificing some ease of driving to gain more capability while putting less strain on the engine. also good for hill starts.
I know 7 speeds with a rangebox is a bit unconventional, but I designed it for use with an H-shifter, most of which go up to 7 gears. Any more gears, and I would have to use a splitter, something which is pretty difficult to get working in-game (i've tried).
To use the transmission, first you will have to go into the vehicle configuration menu, and replace the transmission to the one of them with "Rangebox" in the title. Next, replace the driveshaft with the "Rangebox driveshaft", and then you're all set to drive. You can also switch out the ratio of the range selector as a sub-part in the transmission.
Credit to @ethan5123 AKA "Mr. E" for the video