Do a large majority of discipline issues for a unit originate from the motor pool?

I think that it would be more accurate to say that it is a function of supervision. The motor pool is a well known place to fart off, and bored troops with the Motor Sergeant in his office turns into jackassery. Not to say that the Motor Pool guys don't have work, but it has peaks and valleys depending on maintenance schedules and equipment usage.

CW4 (Join to see) - Chief Warrant; I've had it both ways.

One of the things that helped turn the "bad" situations around was a policy of "If you break it, you are going to help fix it." which meant that the line people got some first hand experience at exactly how difficult it was to do the transport tasks.

Another one was the "You will be on time or else the trucks will be further away than you thought that they would be.". This got the operators to consider that being on time was actually important (they got to drive off even if the troops were running full tilt towards them - which made them feel good about THEIR performance [so they got where they were supposed to be when they were supposed to be there]) and also got the troops to consider that being on time was equally important (watching your transport roll a mile down the road when you are ALMOST on time is a real pain).

IOW, getting the line troops and the support troops to understand that EACH of them had a function that was important in "TGSoT" and that those functions actually interacted to improve efficiency on both sides cut the issues a long way down.

Well, it's a numbers game.

Using 3/1 (my old unit) as an example. We had 5 companies. India (Boats), Kilo, Lima, Weapons, and H&S. Weapons (excluding Mortars) was usually "tasked" to the other line companies, making them smaller so less problems.

H&S was the largest company by about "double." H&S was broken into sections, but.. had a few monstrous platoons within those sections. The S6 (comm platoon) was the largest. Motor T was next, then BAS (which was tasked to the companies), then finally S2/SACO/Scout Snipers (we only had 30 at about half of Comm).

The vast majority of our "problems" came from Comm, followed by Motor T. Mainly because they had a disproportionate amount of leadership for the personnel they had. When you have a Platoon that is running "double" the size, but with a single Lt, a single SNCO, only 1-2 Sergeants (they're rare in the USMC Fleet), and LOTS of first term Marines, things get out of hand.