Originally Posted by chucko

There are two shims in the diffs next to the drive dogs. it either centers the dif or moves it closer to the gear. My unit came with two so that the gear meshes. and it will,... if you push it in... make a grinding noise. take it apart and clean out the grease. re grease with pro long grease about a half a tee spune make sure your rear shaft is as tight and as close as you can get it. you will notice, if you pull it out and turn it doesn't make noise. push it in and it feels like its grinding. also after rebuilding you diffs. run the car on two wheele's for 2 min to break in the diffs and to fling the extra stuff out of the way to make it run cleaner. if you have more issues call horizon service and tell them whats happening.