Truck cant make up its mind

[bamaman315]

Trying to do a carve and while setting up the bits the truck moves to the bit plate and checks the bit , but when it starts to come to the key board side it keeps jerking back and forth. Any ideas?

[Digitalwoodshop]

That is usually 1. A bag Y Gearbox as in the two 685ZZ Bearings and even a bad Shaft. 2. Sawdust inside the Y Encoder. 3. The Y Rails are dirty and need to be scrubbed, especially the lower one with a tooth brush size wire brush. Sawdust builds up on the lower rail. 4. The 4 roller rail bearings are dry and sticking. Need lubrication. Use rags to catch the excess light oil.