Avoid what they call a FLUSH.
Many times they use chemiclals. GM considers anything other than Dexron VI, contaminants.
Have them do a drain/refill. (only half the fluid is removed/replaced).
Or a Fluid Exchange- where they simply pump in new fresh fluid- until the stuff coming out is clear.
Dont know if you change your own oil---- but draining half the trans fluid (GEN 1) is very easy. refilling is also easy.
a how to
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Many times they use chemiclals. GM considers anything other than Dexron VI, contaminants.
Have them do a drain/refill. (only half the fluid is removed/replaced).
Or a Fluid Exchange- where they simply pump in new fresh fluid- until the stuff coming out is clear.
Dont know if you change your own oil---- but draining half the trans fluid (GEN 1) is very easy. refilling is also easy.
a how to

How to drain your transmission fluid.
Couple things went right. 1-Dexron VI on sale.... so I bought 11 quarts. 2-I recently passed 50,000. Since I do alot of severe driving (stop and go LA traffic) I decided to drain the transmission. Note ....this is a PARTIAL drain... as more fluid remains in the trans cooler, lines, torque...