Update 4/19/2021: v1.0.1
I am sure others have tinkered with this, I just haven't downloaded their mods probably (I tend to play my own stuff mostly).
None the less, there are two new transmissions:
Allison V730 EXPERIMENTAL - A Semi Automatic Transmission with 2 automatic gears and a 3rd Manual Overdrive (High) gear. Top speed is the same as the original P12W 4 Speed Transmission except the ratios are spread across fewer gears and if you want the old "4th" you'll need to grab it yourself with the High gear.
Allison CLBT 750 EXPERIMENTAL - A Semi Automatic Transmission with 3 automatic gears and a 4th Manual Overdrive (High) gear. Top speed is the same as the original P12W 5 Speed Transmission except the ratios are spread across fewer gears and if you want the old "5th" you'll need to grab it yourself with the High gear. 1st Gear is the same as Low-High so if you want it to hold first instead of shifting to 2nd, leave it in Low-High.
The purpose and point of these two transmissions is to limit the amount of gear ratcheting/dumping the game does and enable you to haul loads off-road in automatic most of the time. Its a work in progress the more I play missions with it. Eventually I'll copy it to a few of my other tweaked trucks though.
Original 4/17/2021: v.1.0.0. Tweaked P12W with the following adjustments:
-An active suspension with standard and raised heights (toggleable).
-An active suspension with stock & Low Saddle Trailer hookup heights (toggleeable).
-More tire options for stock 57" size and added 65" size including super heavy cat 745 wheels should you want to use them.
-Transmissions - Reduced to a 3 Speed and 4 Speed option. The problem with the game is the forward ratcheting style automatic behavior. IMO fewer gears, not more, is the better answer. Larger jumps between fewer gear ratios means less dumping back to 1st all time. All the range without all the annoying shifting and shift dumps.
-Catbunk log carrier of course.
-3 Slot Beds and Long Fuel tank option.
-Engine Options - I really enjoyed the engines & their excellent descriptions used in the Roughneck Phase 3 update by YKMini based on the original Pacific P12W Roughneck by AnythingInc
If you are looking for a more heavily tweaked & modded P12W, I strongly suggest checking theirs out. Their version was a bit too much for my preferences heh but a very well done mod none the less.
Mostly I tried to keep this one a bit more true to the vanilla P12W with some added usability to keep it competitive with newer DLC stuff.