I have a john deere L120. Its for home use. I changed the oil in it this summer. Replaced with 20-50 Synthetic, castrol. All has been well untill today. It just did not want to go backwards and forwards it has a terrible GROWL! After running it for about 10 min (mulching leafs) The tractor is fine. Reverse is perfect, forward is great with ZERO noise, just the typical hydrolic whine. So my question is. Is there a different oil I should use for winter use? Or am I just stuck with having to let the tractor warm up very well for winter? I use it to plow the sidewalks. Will letting the mower run be enough to warm up the trans?