synthetic vs conventional transmission fluid

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I'm about to change my tranny filter and fluid. was wanting to put synthetic back in but not draining the converter, dont know how. Is it ok to mix synthetic with the conventional that will be left in the converter? Auto is a 2003 Gram Am 2.2 4cylcinder 125,000 miles.
 
Disconnect the top cooler line (if it's similar to my Buick, that's the return line), get a barb and a hose, and do a cooler-line flush with the syn ATF. That will get ~90% new ATF into the transmission.

Maxlife ATF is syn, and easily available.
 
There's no harm in mixing the two. But a complete fluid exchange would be better. Search on this subforum using my name for a writeup on this procedure.
 
I just ended up having syn ATF put in my tranny, even though I didn't ask for it, or expect it - shop used Wynn's universal ATF, and it's 100 PAO fluid!

:p
 
Does anyone have an idea how much fluid the converter on my trans might hold? 2003 Grand AM 2.2 4 cylcinder.
 
For a pan drop change, figure you only change about 1/2 the fluid.
Much better than before, but not perfect.
This is why people do line flushes, or install a drain plug on the pan to do subsequent drop drains [to approach 100% after a few changes].
 
Originally Posted By: rryam
Does anyone have an idea how much fluid the converter on my trans might hold? 2003 Grand AM 2.2 4 cylcinder.


Automatic Transmission, 4T40-E Initial Fill..........6.9 quarts
Automatic Transmission, 4T45-E Initial Fill..........6.9 quarts
Automatic Transmission, Total Fill
4 speed 4T45-E..........12.9 quarts
4 speed 4T40-E..........12.9 quarts

7 vs. 13 quarts. Consider that there will be mixing in the converter as you purge it. 15 quarts should be enough to get it somewhere in the 90% range.
 
I do the pan drop/filter change on my 96 sunfire. there's no pan drain bolt in mine. I must have all kinds of ATF mixed in there over the years with no flushing.
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