A lot of great walls have poor sealing of the bell housing and water is easily able to get in and destroy thrust race bearing. If its not that, others have had issues with noisy and hard to change gears which is overcome by putting in betterie thinner oil than oem when delivered. Oil as per schedule should be changed at 40k, but most owners because of the issues above changed it sooner. There is a face book group and owners web site that might help. I change all oils every 10k and have never had any issues.