Silicone diff fluid goes inside the diff, grease lubricates the ring and pinion on the outside. I generally use synthestic automotive grease but there's Gorilla Snawt, AE, Losi and others have their own grease, take your pick.

ok and what is a good set of tires of mud and a set of tires of snow

on my summit the rc does not move at all ar very little would bad gears in the transmission make that happen

I would check and make sure your slipper isn't too loose.

Nope the slipper is fine it turns good

The summit does nit move when on ground but when I pick the truck up the tires do move but sounds like crap the center drive shafts turn when it sits on the ground but truck does not move can some one help me

Is it possibly stuck between hi and low? If not does it do this in both high and low?

Yes it does it in both i have reviese a little bit tho

Can you make a video of what it's doing?

Sure give me a min

It is not doing it right now bit it does it on and off

If it does it again whip the camera out, preferably with the body off so we can see what the gear selector servo is doing.

Ok I am guess it is the diff tho

I found the problem with my rc it was the diff bit thanks for all the help
What would be a good set of tires of my summit

what is your opinion on big joe tires for my summit or are trenchers x better