In a message dated 97-06-09 13:59:30 EDT, kersey@outdoortech.com (Bo Kersey)
writes:

> Taking one quart out and replacing it does not do that much good.  I mean, 
>  the quart that you take out is mostly new transmission fluid, isn't it.

No.  
Assuming (for the sake of nice even round numbers) that the trans held 5
quarts and that you drive the van in between to circulate & mix the fluid.
 Outside the US, please substitute the word liter for quart or qt.  :-)

The first quart replaced is 100% old fluid.  You'd have 4 qts old & 1 qt new.
The next quart replcaed is 80% old, 20% new.  You'd have 3.2 qts old & 1.8
new.
Then...64% old, 36% new.  You'd have 2.6 qts old, 2.4 new remaining. (48%
new)
Then...52% old, 48% new.  You'd have 2.0 qts old, 3.0 new remaining. (60%
new)
Then...40% old, 60% new,  You'd have 1.6 qts old, 3.4 new remaining. (68%
new)
Then...32% old, 68% new,  You'd have 1.3 qts old, 3.7 new remaining. (74%
new)
Then...26% old, 74% new,  You'd have 1.0 qts old, 4.0 new remaining. (80%
new)

Then you changed 3 qts of fluid with new when you replaced the screen and
seal.
You'd end up with only 0.4 qts of the old stuff in there.  That's 92% new,
compared to only 60% new without the "flush" technique.

This gradual change MAY help keep the seals from leaking too.  I haven't had
a leak between the 100,000 mile change and the current 130,000 miles on the
van.  I made the change over several weeks with anywhere from 1 day to 2
weeks between the 1 quart fluid changes.

Regards,
Jim Davis
87 GL Syncro
88 GL Wolfsburg