Just replaced both drive motors on my 763. One of the old drives had a stripped stub shaft and the other was weak and too far gone to be rebuilt (according to the hydraulic shop). Anyway, the new drives work great but the groaning noise that was present before is still there. Noise is present only when the drives are engaged and is worse under load. Some discussions seem to indicate the inline filters may cause this, and I've replaced the one near the left drive motor but not the one at the reservoir (afraid I may rip the fitting out of the tank while trying to remove it). Could that filter could be causing flow issues thereby generating the noise?