The ball differential is a vital component that affects the way the car handles. During assembly, I made sure that I kept all parts clean and free of contaminants.
You can use your grease of choice based on what's popular at your track. For the Tamiya track, there's a mix of those who run normal greases and those who run Mobile 1 red sythnetic grease. Back when we used to run rubber tires on the F103, all of the really fast guys ran Mobile 1 grease religiously. We set the differential to slip between 6 inches to 1 foot under full acceleration from a dead stop. Keep in mind, there is a fine balance and requires a bit of time and effort finding the sweet spot, but once you nail it, you can hammer the trottle on corner exit without any suprises...and that is a good feeling.
That being said, I deviated on this build by building the differential similar to my touring cars. Associated red label silicon grease on the plate and balls, and Mobil 1 or Tamiya's VG thrust bearing grease on the thrust bearing.
Important tip: When assembling the differential, do not fully tighten the lock nut. You want to snug it up until the differential action starts working. Fully tightening and loosening a quarter turn as instructed by the instructions may crush or deform the diff plates, diff balls, or thrust bearing. Final adjustments should be done at the track after break-in of the diff.
Parts and a few hopups for step 5:
Building the diff with AE red label silicon grease:
After assembly, the differential action felt somewhat dry and gritty. I wasn't satisified with this and took it apart and degreased everything.
If you noticed in the previous pictures, I was using the hop up thrust bearing. There's a reason why we never used it when we ran F103 rubber cars. The were inconsistent as some would be great out of the pack while others were junk. They didn't last long either with the way we set our cars up to slip. Lastly, there was a time when we had a huge supply of stock thrust bearings; we wouldn't think twice tossing out a semi-worn one and replace it with a new one...just because we had so many
Okay, so now that everything was taken apart and degreased. I rebuilt the diff with Mobil 1 and used the stock 1150 bearing with cone washers as the thurst bearing.
Rebuilding the diff with Mobil 1 synthetic grease:
Step 5 completed:
Ah...smooth like butter.