Hi! This is my first post since joining up - just bought myself a new Cat SX and am now overcome by a flood of nostalgia! I'm a bit surprised nobody else has replied to this question given the serious depth of knowledge here!
Anyway, my first CAT was an XLS and my third was a ProCat - I haven't had them in decades (mum made me give them away - gutted!) so this is from memory:
7-cell saddle-pack chassis replaced 6-cell stick pack chassis
Rear diff in solid "drum" with solid layshaft like TopCat (which almost everybody replaced with a one-piece MMS unit)
Rear belts upgraded to TopCat belts (wider)
TopCat-style rear suspension consisting of "A" frame lower arms, multi-point adjustable turnbuckle upper links, multi-point upper shock mount, redesigned uprights and one-piece lower arm mounting blocks. Rear toe-in was no longer easily adjustable.
Narrower (BRCA legal?) front bumper
TopCat-style O-ring wing mounts
Optional overdrive front pulley (can't remember if this came in the kit or as a hop-up)
Adjustable front belt tensioner (i.e., two screws in the diff housing)
Rose joints replaced ball joints in various locations (I think! Can't remember if these were my own mods!)
Mini spikes replaced full spikes
White wheels replaced silver wheels
New body, obviously!
As far as I remember, the front ends were largely the same. Same shocks, one-way roller drive shafts, crash-back front end, etc.
I remember putting the TopCat rear wishbones on my XLS in the run-up to the IFMAR Worlds in Australia (1989?) but this made it TOO long - tendency to flip during cornering and less control mid-flight. As we later found out, the actual ProCat release had a new design of wishbone that handled much better.
I so wish I had kept all my old cars...!
