There are several bulletins out for the L3301 and L3901 and also the L4701 tractors. If you are the original owner, you should get a letter from Kubota. And your dealer should call you.
Partial list of bulletins:
PSB-2014-054 (PCV vent hole plug)
PSB-2014-052 (poor hydraulic performance)
PSB-2014-027 (front axle pivot rocking force)
PSB-2014-061 (battery cable campaign)
PSB-2015-051 (L-01 series ECU reprogram).
PSB-2015-007C (L series cold weather kit, important for those north of the Mason-Dixon Line.....)
Call your local dealer and ask them about it. Some of them have a transportation allowance, so that the dealer can pick it up on Kubota's dime. Some of them that have the allowance are about to expire and if the campaigns are not done and the allowance expires, they won't pay transportation and/or service call fees...so the owner would be responsible. Again, call the dealer with your serial number and they'll give you a rundown.
The only major one is PSB-2014-027, which dealt with a weldment issue on the front axle holder. 99% of them were not affected (had to be checked) but a few had to go back to the factory to have a new front frame installed. The rest of them are easy. The ECU reprogram is a big one and it eliminates PO336 from showing up in the panel during normal operation and therefore de-rating the engine's power. If PO336 is left running, the tractor will not perform a proper regen and can plug the DPF prematurely. Need to do the reprogram ASAP on affected tractors. Is yours affected? Call dealer and find out.
The PCV vent was plugged at the factory during the painting process (to keep paint out of the vent hole), but some of the plugs didn't get pulled after painting. Sometimes the PCV vent would not "vent" properly and cause oil to be pushed into the air intake. Of course it's a diesel...it will run on it's own lubricating oil, and that's what the issue was. It was very rare to find a plug still in a PCV. One out of maybe every 75 tractors but Kubota wants ALL of them inspected. While they're inspecting, they can also do the battery cable campaign if applicable, and ECU reprogram if applicable...all depends on your particular serial number. Some were eligible, others not.
it would be nice if the bulletins weren't "confidential and proprietary". In other words, should not be distributed. But if you call the dealer with your numbers, they'll look it up in about 2 minutes and tell you whether your tractor is done or not, or if it's even eligible. Takes no time at all, and on some of them Kubota even pays pick up and delivery. It's really a low-hassle deal. If you own an L3301, L3901, or L4701, call a dealer to get this stuff addressed.
I have been keeping a list in another thread and will add this info there too. Thanks!