Kenny, you're new to the forum and maybe new to the hobby so on both accounts welcome.
I run mostly the cheaper mid-1980's to mid-1990's K-Line and Lionel locos. Many of these diesels did not come with horns. And the ones that did, well those horns leave loads to be desired. All of these locos came with truck mounted DC can motors, and have a natural tendency to "growl" if they have dual DC motors. Single motored diesels and steam locos do not make this noise.
It was this noise element, that by accident I started messing around with DC power. I now run my whole layout on rectified DC current from a normal Lionel 1033 transformer, the best one Lionel has ever made IMHO. I do pull the circuit boards out of the locos and rewire them as you mentioned. The DC can motored diesels with dual motors DO run much smoother, more constistanly speed wise on curves and run quieter.
There are plusses and minuses to everything. Losing the circuit board on smaller diesels like the mid-1990's issued Lionel Industrial Swithcers allowed me to add a lot more weight, so now these little guys can pull almost as good as anything else... I've had them pull as many as 25 cars, but 8-12 cars are zero problem for them now. I don't like the cheap diesel horns, and I don't mind off-board sound... on a small layout you don't notice as much anyways. I rewired a Lionel steam whistle from a tender into a Plasticville Hobo Shack and I have my own custom made diesel horn. Plus I have the MRC 312 Sound Station which I wired additional speakers into, so I have plenty of sounds. I don't and will never run TMCC or DCS, so that wasn't even a consideration. If TMCC equipped locos become the same price level as normal locos, and the system itself drops significantly in price, I might consider. But given Lionel's history, that will never ever happen.
I have too many problems with the computer I am sitting at to ever be interested in having computers on my train layout. And contrary to popular opinion, I actually have fun with no frustration and have NEVER had to send a loco back for repairs.... something many TMCC owners cannot say. But it's your choice. For some, it's worth it. For me, it's not.
You do lose the "neutral" position running DC as I do, but that's not such a big deal. I've rewired many of my operating cars, removing slide shoe trucks and mounting a small switch beneath the car. So for example, with my Lionel Barrel Loading cars, I hit the switcher and can run the train to the place where I want to unload. The engines use much less current on DC minus the circuit boards. When the barrel car is in the proper spot, I hit off the power to the loco via many insulated blocks, turn the track power up higher and the car operates.
By using DC current, I found normal light bulbs in cars would run dimly, so I replace all of them with lower voltage 6V bulbs instead of the typical 12-18v bulbs. So now I can have more illuminated cars on the track using the same transformer. Same goes for my buildings and street lights... I use lower voltage bulbs using another 1033 and find it powers the whole layout because the bulbs themselves draw less amperage.
I find you do need to clean the track and car/loco wheels a little more often using DC current, but I already was in good habit on this one too, so no big deal. You can make your own DC convertor box using a full-wave bridge rectifier with a DPDT switch, or you can look for the one Lionel made duing the 1980's- early 1990's for the G scale market (so large scalers could use normal Lionel transformers to run these trains).
What started as a limited experiment, has now taken hold. All my locos have lost their electronic circuit board eunits. Williams locos run fine as is, as they use a horizontally mounted larger DC motor and their gearing is better, so their locos never growled like the others. My postwar and MPC vintage Lionel locos run fine as is on the DC current, though the mechanical e-units like to lurch a little bit. The solution here is to bring up the power slowly and listen for the mechanical e-unit to engage. Again, no big deal... just takes a little getting used to.
You wire up everything just the same, save for the inclusing of the convertor box between the transformer and track. If you don't have a good transformer, you could buy an MRC larger DC power pack, but you WILL need a larger one. And they cost well over $100. The newer MRC ones will run your trains a little bit more smoothly, but for me, it wasn't worth the extra money. It's cheaper to use a used Lionel 1033 with a conversion box of some kind.
Hope that helps.
