It is a beauty ART, and sound is great. Greetings for this nice buy, Daniel
I opened up all four gearboxes and grease was present on all gears, but I did add some and spread it evenly. I then oiled all axles and bearings on all three units with LGB's synthetic red gel oil. Cleaned slider contact shoes and reassembled. Alas, the squeaking returned! Two possibilities remaining are the 8 contact sliders, or possibly the truck wheelbase is too wide for the LGB 1500 (R2) radius track! I will have to ponder this puzzlement! Your suggestions are welcome!
Sound system and motors are operating fine. Squeak is external so may be wheels or contact slider shoes?