The TCS MZA4 decoder is designed to fit older style Micro Train locomotive's chassis (including GP35). Micro Trains changed the chassis design and our MZA4 decoder will fit into the new locomotive releases (including SD40-2) but will require a slight modification to the posts on the chassis. Pictures below show before and after the modification. The posts holding the decoder in place are milled to accurately accept the decoder.
The three pictures below show the "New"Style chassis before posts modification.
The Three pictures below show the posts modification we did here at TCS. It will allow you to use MZA4 decoders in the new MTL Chassis style.
Using a dremel tool with a cut-off wheel cut into the notches in the frame and remove approximately half of the material between the notch and the outside wall of the post. The images below show the completed modification.