DCC Speed Steps

you don't say who's DCC system you are using , If its NCE there is a button on the hand held to go from 28 to 128. or you can put it on the program track and curser thru the menus and change things that way rather than mess with CVs.  decoders with 14 speed steps have been gone a long time. 

Maybe the problem is using 17 as a "short" address.   Addresses 0-127 are used as consist addresses and assigned in order by most systems (NCE) as consistes are built unless programmed otherwise.    You could try making it "017" to force a long address.     Using addresses below 128 sometimes confuses systems, since they want to control these for consist numbers.

Another solution is to make both "117" and see what happens.   If you are going to run them together most of the time, use the same address.    this is called "basic" consisting by some authors.   It is the original way to do it.

Decoders (and not all) usually support either 14 speed steps or the 28/128 mode.

When the decoder is set to 28/128, it automatically accepts either 28 or 128 steps as transmitted by the DCC system.

i.e. the throttle/command station does the switching. So you need to change your throttle settings for the unit you want to change.

Most DCC systems "remember" the 28/128 setting on a per loco address setting.

It has nothing to do with long or short addressing. As Rick said, the NCE has the setting as a dedicated button.

If you still have issues, please indicate the make and model of DCC system you are using, also the decoder model numbers might help, but I'm pretty sure that is not the problem.

Now when you get into custom speed tables, there are decoders out there, notably TCS that have problems...

Greg