TOPIC:

I recently purchase a TRF 501X World Edition which had been built and modified.  While taking it apart and trying to figure out what was original and what wasn't, I ended up doing a bunch of research into the short history of the 4WD TRF buggy line to figure out the differences between the models.  Below is what I came up with.  If anyone has anything to add (or contradict), I'd be interested in more information.

501X (49401):  Center motor, dual belt 4WD, carbon chassis, ball differentials, slipper clutch

501X WE (42105):  Cam bearing posts on center pulley, 18T center pulley instead of 16T, 91T spur instead of 96T, improved slipper pads, 37T diff pulleys instead of 36T rear and 35T front (no overdrive), 12 balls in ball diffs instead of 8, strengthened upper arm mount using different holes and allowing lower installation, extra holes in rear shock tower (unused), different default front shock mounting holes, 10.5mm pins in universal shafts instead of 9.8mm, aluminum rear uprights with longer ball joints, aluminum caster blocks with longer ball joints, front and rear sway bars, new delrin pistons and rod guides replace W parts tree, longer piston rods, softer rear springs

511 (42139):  Extremely similar at first glance incorporating many of the updates of the WE, new chassis plate with slightly shifted components (same profile), center bulkhead altered for easier slipper removal, split (2-piece) upper arm mounts, split rear suspension mounts, modified upper bulkheads, less overlap on upper decks, slipper stiffener removed, modified lower arm geometry, rear upper links moved to forward side of uprights, different default front shock mounting holes, does NOT use upgraded WE delrin shock parts, under tray attaches with more screws and no tape, new body, separate version available with gear differentials (42213)

502X (42183):  Almost totally new, switch to shaft drive and longitudinal motor, same body as 511, center bulkhead is completely different, ball diff similar but with a ring gear instead of a pulley, front and rear bulkheads are now plastic, new steering cranks, suspension is same as 511, all electronics repositioned

503:  This is an evolution of the 511, not the 502X, aluminum chassis instead of carbon, longer wheelbase, unequal length drive belts, gear differentials, new shock towers, different style universals using retaining rings instead of set screws, new uprights with more adjustment options, big bore dampers, new cantilever servo mount, same body as 511


It is interesting to me that the 502X went to shaft drive in the middle of the series for some reason, then the 503 went right back to belts.  I obviously haven't driven all of these to compare, but based on the specs alone it feels like the 511 and 503 are actually downgrades compared to the World Edition.  I wonder if there is anyone out there that has all (or many) of them to directly compare.