5AT with External Tranny Cooler
 

Hi All,



I am at 1015xx miles on my 03 G Coupe



at around 100xxx miles, I had my Rear Main Seal Changed + Had the torque converter drained & filled with new ATF (Matic S), along with some leftover being drained and filled (around 6 QT of ATF)



I have checked my ATF recently and it was light-ish brown. So I got worried and did a drain and fill again, around 3.5 QT of Matic S.

I am not sure if it is still brown but should I be worried if it is?


Should I change my external AT cooler (Napa Oil Cooler)? Perhaps with something like:


this https://www.mishimoto.com/10-row-oil-cooler.html



or



https://www.mishimoto.com/19-row-oil-cooler.html


Will post pics later of the tissue colors.


TIA

The oil cooler is not causing your fluid to carry particles of the clutch plates and brake sleeves, that's normal and that's WHY you drain/fill the fluid every 30k. If it's any color other than red it's because of the amount of particulates in the oil, the normal interval for fluid D/F is 30k miles but in your case I would just drain/fill with every oil change for the next few times until the fluid starts to look normal again.

If it's actually BROWN I'd do multiple drain/fills consecutively to flush as much crap out as possible then another drain/fill with the next oil change. If it continues to look bad after the next oil change then start shopping for a new transmission because the one you have might be quickly disintegrating.

Here is the color of wiped at fluid as of today.
https://cimg1.ibsrv.net/gimg/g35driv...de3879888a.jpg

Would overfilling contribute to browning of the fluid??

Here is one before drain and fill:

https://cimg0.ibsrv.net/gimg/g35driv...bf45d1a19f.jpg


Regardless though, I have no slipping issues etc. The color just concerns me.

Drain your fluid into a glass jar and let it sit for 2-3 days. Take a pic and post it.