XRAY - Model racing cars

Hi, I was stupid and did not break in my diffs. Unfortunately, I ran it for about five minutes total as set from factory, which I assume is pretty loose. Then, some guys at my LHS tried to help me out, since my diffs were messed up, and tightened them fully. Before that I had run them quite tight for a little while, but untightened them since it didn't sound good. They are now basically locked front and rear, and I have run it hard for around 5 minutes. But, the guys at my LHS have suggested that there is something wrong with my diffs. I'm not quite sure what it is, but apparently they are not running properly. So will I need some new diffs?

Take the diffs out of your truck/car and dismantle them, look for anything that may be damaged in them and if everything is ok rebuild the diff and just flip the diff rings round and begin again, run the truck/car for a few minutes and bring it in and tighten the diff by small amounts maybe quarter a turn until your happy with the way the truck/car feels. hope this helps

You should never lock a ball diff if you want it to run smoothly. It tightens it so much, it puts small dents into the balls and washers, so they wont ride smoothly when you loosen.

Try what Sam suggests above (dont forget to clean everything first with electric degreaser then you only need a slight amount of diff lube), It that fails then go and get new main balls, washers, and thrust balls.

You might even check them before reassembly to see how they look (especially the thrust washer and balls ones as they would go first). If you decide they are toast, you could then safe a few bucks by flipping your main diff washers over for the new balls. (In other words, you would only need to get new main balls, and the thrust washer assembly).