Thread: Auto Transmission Flush on High Milage Vehicle

Originally Posted by 101RRS

So how does a fluid change dislodge contaminants etc that the normal operation of the gearbox would do anyway with fluid being pumped around at high pressure as the vehicle is being driven along.

Sorry not following the logic.

It really shouldn’t with modern gearboxes and fluids. It is very much old school thinking from a time when an auto would only last 200-300,000kms in the first place.

Of course if you don’t change the fluid in the first 200,000kms and then change and wonder why it failed very shortly afterwards you should be able to work out what the real problem is.

Originally Posted by 101RRS

So how does a fluid change dislodge contaminants etc that the normal operation of the gearbox would do anyway with fluid being pumped around at high pressure as the vehicle is being driven along.

Sorry not following the logic.

The old school logic in my time in the trade was that ATF (Dexron at the time) has detergent properties, and so if you put new ATF in a worn old tranny in a Valiant or Falcon etc then the crud holding the seals in place would be dissolved and 1) cause the clutches to slip or 2) block up the oil galleries in the valve body. In any case, a trans in this condition is on its last legs either way.