Saving trucks is not as hard as you might think. I've seen comments before, like the Soviets lose 20 truck factories, so they are in trouble. That's ridiculous. First off, the Soviets have 140 domestic truck factories. After 1941, each factory produces 5.5 trucks per week. So the loss of 20 factories represents 110 trucks per week. That's 5,720 trucks per year. In 1942, Lend Lease provides 1,000 trucks a week, 52,000 a year.
In 1943, it's 156,000 per year. So will the loss of 20 factories hurt? A tiny bit, but in no way is it even remotely a game changer.
Here are some of the ways to find yourself hurting for trucks:
Building too many many tank support units.
Building too many light rocket regiments.
Keeping motorcycle regiments around. They provide no real unique advantage as a combat support unit.
Keeping a lot of level bombers on the map. Air bases with level bombers require far more trucks than any other type of aircraft. So the trucks are stripped out of the motor pool needlessly.
Building too may tank or mechanized corps. This is later in the game, but be mindful of the fact each mechanized corps can require 2,500-3,000 trucks. By all means build them, just don't go crazy, like building 15-20. I tend to like about 8 mech corps and 24 or so tank corps.
Having too many tank units far from railheads, particularly during first blizzard. It's easy to advance with lots of tanks while recapturing lots of territory. Then you look at the truck supply and realize you've lost thousands of trucks trying to supply all these tanks. I now only deploy about 20% of my entire tank force forward during first blizzard. The rest just stay back and gain experience. Same for airbases getting too far forward, keep them close to the functioning rail network.
Net result if you follow these tips and don't lose all your domestic truck production, then truck shortages are not so much an issue.