Funny, I saw those for the first time today on rcmart. I'd always heard that completely locking the diff in your mini was a bad thing.

I did have a little personal experience regarding this a few weeks ago. I built a new ball diff, loaded it with anti wear grease and cranked it down. It was essentially locked.

The car handled like crap! If one wheel got a little grab it would pull ahead, changing the suspension geometry so the other side would grab, and so on and so on...the car fishtailed a little.

I suppose if you are racing on the right surface it could work though.

Jim