The first 4 are old, so you need a 5 pole amrature, field magnet, and decoders. Unless you only want the old motorin place with a decoder, you can do that, but they won't have acceleration or braking delay, nor speed compensation for gradients.
The 3756 is already digital with high efficiency motor. You can upgrade it to sound if desired.

Hi Roger,

Sometimes models have different motors over their production lifetime so it is always worth opening up to see what you have in place.
Posting pictures of the internals will allow many of the members to assist easily in confirming exactly what you need. I've provided marklin part numbers below in this instance.

Previously shared is this PDF that contains models and their respective motor specs http://up.picr.de/8986407iuw.pdf

Presuming the catalog numbers of what you have are as per the pdf you will require 3x Marklin 60941 - High-Efficiency Motor Conversion Set DCM

A decoder giving sound would be the likes of the mSD3, you have a choice of:

• 60975 Märklin SoundDecoder mSD3 steam locomotive noise
  
• 60985 Märklin SoundDecoder mSD3 steam locomotive noise NEM-652
  
  

In short the 60975 takes up more room but is more flexible if a decoder needs replacing as another can be clipped in. Replacing a blown 60985 requires a lot more work routing wires again. You may have to make an assessment on which option is best suited for each loco.

If you want to put sound into the 3756 then a Marklin 60977/60987 would be the respective retrofit replacements.


In terms of lights you will typically want to get 2x Marklin bulb holders 604180 and 2x digital (22v) bulbs 610080 per loco assuming front and rear lights are in place.


Your parts order list might look like this:

3102, 3082, 3085 for each: 60941 Motor Kit, 2x 604180 Bulb holder, 2x 610080 Bulbs, 60975 mSD3 (Steam)
3756: 60977 mSD3 (Electric)



I have semi-recently upgraded my 3102 - produced 02 of 1979 - it took a DCM motor kit 60941, I ended up putting in a 60975 - Marklin mSD3 SoundDecoder (Steam) into it but some trimming was required internally of the tender plastic to get the board to fit nicely. It is not on the mounting post because it was too high to fit and have room for the speaker. Equally a 60985 perhaps fits better but you have to route the wires where you need them including the front lights and smoke unit, i did end up reusing some existing wiring with the path i chose. I also opted to fit the "suppression chokes" in the tender as i had clearance issues when the chassis was articulating with them attached to the motor plate.
The following gives an idea of what you could do (excuse some of my wiring work)

I tried a few Uhlenbrock 76200 in my time in order to keep the original motor and be less 'invasive' with my conversions.
I had to replace all of them due to poor performance.
I see that Marklin makes a decoder for AC motors but have never tried one.
Definitely a 5 pole motor is much better

When using the Uhlenbrock 76200 decoder, the motor is converted to a DC motor to allow load regulation.
The Märklin decoder keeps the AC/DC motor as it is without load regulation. Never tried it, but I would not expect good behaviour from such a decoder.
Conversion with a permanent magnet is the better approach. Using an ESU decoder, an ESU magnet and keeping the original three-pole rotor can give satisfactory results.

Uhlenbrock decoders can not be read by a Marklin CS 2, or 3, but parameters can be adjusted.