Mitaka

I was very interested in your post about using tiptronic to save the transmission. by doing that do you completely avid using the solenoid valves. what exacty are these valves. give some more info if you can please

ryoung

First, I'm no expert on automatic transmissions, but here my guess anyway.

I'm assuming that old ATF and/or a partially plugged tranny filter results in cavitation of the ATF and cavitation damage to any modulating control valves. It's the partially open modulating valve that will be the first to cavitate. When these same valves operate as just open/closed solenoid valves, they function just fine, even if previously damaged.

Several have reported that putting the tranny in Tip mode eliminates the "hunting" for a gear at light throttle. I believe using the Tip essentially eliminates any modulation of the solenoid valves that are handling up and down shifts, and the valves just open or close. If all this is correct, running in Tip mode should increase the life of the tranny.

Pages 35-40 of this pdf for the ZF 5HP24A tranny show the control valves; it's a plumbing nightmare.<ul><li><a href="http://www.zf-group.com/pdf/5HP24A.pdf">5HP24A pdf</a></li></ul>