They sell an aerosol trans flush, parts store may have it or the trans shop may be able to get you a can...

 

They shop gave me a can of the flush. Does is matter which line I run it into?

Also what fluid do I need to run in this, its a 99 4l60e?

 

Dex 3 would be optimal.... 6 will work, but gm calls for 3

 

Run it through both lines, flush and backflush!!!

 

I'm guessing the way you out it that dex 3 is hard to find?

 

Dex 6 is at least as good as dex 3. Walmart has a ton of dex 6 so that's what I run

 

If I was worried about **** in lines and the cooler I'd get all new stuff. So that's what I did.

Look at the true cool 40k sticky!

 

Dex 3 is available... But it has been superceded by dex 6..... Im running 6 because the dealership i work for doesnt have 3

 

Even new coolers should be flushed.... Nothing worse than a piece of styrofoam stuck in a cooler!!!

 

I got it all flushed out good, followed the can flush with some air. Now I got to finish connecting everything. Had to wait on the o2 sensors from the dealer. That driver side wouldn't be fun once the trans was back to the original position.