on my Valeria glamish RC buggy the slipper grinds when its tight or loose. could it be the pinion in differential?
rhanks
Kenny

Most of my slippers squeal when they slip, so there is a good chance it isn't the slipper. Could be the pinion/spur but if they are grinding you should be able to see a flat spot on the spur. And it could be an internal gear or the differential as you noted. If you made a video with it running and making the sound perhaps we can help you trouble shoot it.

Sometimes a rock gets where it shouldnt be and will make a grinding noise as well.

I replaced spur gear already but it clicks when I give it throttle. I took 3s out and put a 2s battery in it and still the same sound. I'll upload a video tomorrow after work. About this time. I hope its not in the differential but I'm thinking it is. Its a discontinue RC car now because of spur gear and slipper isuues I've read about.
Thanks for reply and keep looking for a video.
Thanks
Kenny

I would check the idler gear inside the transmission, they tend to strip if you have your slipper set too tight