The Blade 700X has a great TT gear design and plenty of robustness to it, but unfortunately the gear lash is a bit off. It was most prominent in the rear but still found in the front as well. Good news is this is easily remedied. If you remove the TT gear from the tail box and front tail transmission a shim can be slid over the TT gear and then inserted back into position. Due to small differences in manufacturing you’re going to have to try different size shims and possibly sand down your shim to get a smooth gear mesh with just a very small amount of lash. I’ve found that the thin shim used on the Blade 700X main shaft worked on my heli. Also, if you have some Trex 700 main shaft shims those are the right diameter as well. The ID of the shim needs to be just a tad bigger than 12mm. Doing this will dramatically increase the strength of the tail drive system!