Drop in decoders

[RockGp40]

Which manufacturers of diesel locomotives are drop in decoder ready in N scale?

[MK]

Almost all of them now a days.  Atlas, Kato, FVM, Intermoutain, etc.

[nickelplate759]

Almost all of them now a days.  Atlas, Kato, FVM, Intermoutain, etc.

To elaborate - all of the above (Micro-Trains too), if the loco is of fairly recent production (say the past 5 years?)
For models that have been run (manufactured, not run on the layout) multiple times, the older runs (more then 5 years ago maybe?) may not be - for example, the original Atlas/Kato SD9 is not drop-in-able, but the current Atlas/China run is.

I'm not aware of drop-in decoders for any current Bachmann diesels, but some come with a decoder (like the NW2) and some have a circuit board that makes it easy to add one (like the H16-44).

Both Digitrax and TCS publish lists that match up models with their decoders.

[MK]

For Katos, the blue boxes are not DCC ready.  The green ones are.  For Atlas, they are usually written on the box as "Decoder Ready".  Also, for Atlas Classics where Decoder Ready is not indicated on the box, TCS had a "two part split" decoder that you can use.  They are semi-drop-in as you do have to do some wiring and soldering but the two piece decoder replaces the two piece original light boards.

[Ike the BN Freak]

For Katos, the blue boxes are not DCC ready.  The green ones are.

Not always, the E8/9s in blue boxes are DCC ready. And first runs of C30-7s and SD45s came in green boxes, however are not DCC ready