Zero Turn Mowers

I have a CZ4817 (2003 Model) zero turn mower, and I'm trying to troubleshoot a recent right wheel drive chatter issue. The drive will run fine when up to speed, but while turning right the drive starts/stops in a very fast jerking manner. It's very slight at low speeds and becomes more noticeable if you're turning at higher speeds. The mower is still very much usable, but the issue is concerning me. The manual shows nothing about changing the hydraulic oil in the hydro-static drives or checking level. Could the issue be caused by air? Are there any other things I can look for on these drives? Thanks for any guidance.