What ATF to use in an TH400?

IN71GS

Member
Should be putting the motor and trans back in my GS soon. I know that Dexron II is not available, so what is my best choice for ATF? When I added new cooling lines a couple years ago after putting headers on the car, I topped it off with a product from Advance Auto that is just called Multi Vehicle ATF. It is marked as approved for GM prior to 2005 and list being a replacement for Dexron II. Had no problems with it, but now am just about doing a complete new fill with new converter and pan on the trans. Have also seen a product marked Dexron/Mercon that also says it is interchangeable with Dexron II. Current Dexron products claim to be backward compatible, but I knw they are much thinner, and I have been told the may not work so well in the older transmission. Thanks
 

LARRY70GS

Active Member
All Dexron is backwards compatible. I use Dexron 6 synthetic in both my GS and 98 Riviera (200,000 miles on the original transmission)
 
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