Thought I would share this reply in case any one else was wondering...
Originally Posted by JS
I saw your post on the Cup Racer thread regarding using a spool for the front and used a Pro4 Spool.
Would you be able to tell me all the parts I need to get the same setup for my Cup Racer?
Here is what I got so far from the pages that I read:
HPI Pro 4 Spool – 75168
Bevel Gear Set – 61433
Are there any other parts that I would need?
Are there any special modifications or would the parts just drop in with no issues?
Also - what setup are you running for the rear?
Gear diff / which spring?
Thanks for your time, Jeff
Boy it's been a few years since modding the diffs. Just did a tear down of my CR and it looks like I've settled on;
Front- I moved the stock REAR ball diff to the front. I figure the metal diff gear would last longer (the front tends to be more fragile on shaft drive cars). I now tightened the front diff to the point that it ls almost locked and replaced the diff grease with heavy 100k silicone. It now acts like a spool but with a little give for limited slip If I hit anything.
Rear- I built up a 2nd diff using mostly stock CR ball diff parts but replaced the metal gear with a PRO4 diff gear. We run Mabuchi motors here so I wanted both diffs as light as possible for obvious reasons. You have to shim the diff so that the gear does not rub the gear case.
Do not overtighten F or R gear case or it binds up the entire drive line.
That's about it. Nothing too modified
I will post this on the CR thread just to share.