jinman
Rest in Peace
- Joined
- Feb 23, 2001
- Messages
- 20,387
- Location
- Texas - Wise County - Sunset
- Tractor
- NHTC45D, NH LB75B, Ford Jubilee
Can anyone fill me in on what charge pump cavitation is?
Since I brought it up, I can tell you that it happens when a pump is being forced to rotate faster than the pumped fluid can flow. The pump pushes all the fluid out, but can't suck hard enough to get the inlet fluid to flow because of the cold viscosity of the fluid. It just can't flow fast enough. Therefore voids are developed at the pumps impellers and may cause erosion as J_J mentioned. Many HSTs have charge pumps that supply positive pressure to the HST pump to ensure it does not also cavitate. This allows the HST to operate efficiently throughout a range of temperatures. Some HSTs don't have charge pumps and only the HST pump is there to draw fluid from the reservoir. When a pump pushes out fluid but can't replace it with inlet fluid, there is cavitation. This explanation is probably way oversimplified, but it gives you an idea of why your transmission works better when the fluid becomes warm. By selecting a fluid that has a lower viscosity, you can prevent this problem. You either pay for the expensive fluid or wait for your tractor to warm up.