Quote:
Originally Posted by Quicksilver
Interesting
After the transfer case fluid has been changed what specifically needs to be updated via computer in my 2005 4.4, and why.  |
Your x drive X5 (2004 onwards) has clutches in the transfer case that direct power to both front and rear axles. Those clutches are wet clutches, and the actuator presses the multiple clutch plates together. The transfer case expects a certain engagement rate (sort of like how fast you let a manual clutch out, or how slowly). When you change the fluid the wet clutches engage differently as the fluid is different. The transfer case has stored (adaptations) how the clutches react. When you change the fluid you need to tell it to go recalibrate itself, because it doesn't know there is new fluid there. In general terms, it moves the actuator from fully engaged to fully disengaged, and checks the range. Then it measures the % slip and adjusts engagement pressure to get the right % slip. All resetting it after a fluid change does is tell it that the fluid is now different, so just go do that self-calibration again, and use the new stored value, not the old one, for daily operation.
Not doing that would be like changing out some part that you normally adjust from time to time, but not resetting it and just trusting that the old setting would be fine. An example would be valve clearance, when you change camshafts. Someone will say that theirs was fine, no problems. OK, it could be perfect. But it could be too loose or too tight, and the right way to do it is to check valve clearances. Another example would be getting an alignment after changing suspension components. In the case of the x drive transfer case, let it do a self calibration because the downside of it slipping continuously, or being too tight, could be far more costly than the consequences of not changing the fluid.
There is another setting that may need to be reset. It is the one that says the fluid characteristics are now out of the expected range, so change the fluid. After changing the fluid, that one should be reset. But it likely has less to do with how it operates, and more to do with whether the next warning will be relevant or not.