Who makes the best performing synthetic auto. trans. fluid on the market ?Also using factory thermostat [197 degree], is it best to by-pass the radiator cooler & pipe directly to & from the trans ? Also I'm still useing the stock converter .

 

I believe the only one people have success with is Royal Purple, but 95% of the people here will tell you to stick with dexron III. Do a search, this comes up atleast once a week!!!!!

 

synthetic fluid is a BIG no no in 4l60e (or any auto trans) the fluid is too slippery and causes the clutches to slip....im sure more will chim in and tell you the same!

 

Well , I just read a report on general motors new DEXTRON VI synthetic blend auto trans. fluid that is to replace all other dextron in all years of GM vehicles. Cost about $4.85 per quart. My dealer now has it in stock. I will be power flushing my trans. & watching the clear return lines until they turn a bright & beautiful red. Then we'll replace the pan & gasket with B & M's alum. finned deep pan with of course a brand new filter. Then we will re-route the pressure & return lines to by pass the radiator cooler directly to the B & M 24,000 lbs. plate cooler mounted horizontally under the front facia on the passenger side & of course double clamp all lines. VIOLA, done.

 

Same thing i'm doing, and mine is mounted in the same place too. I will be flushing my Dex 3 for Dex 6 and bypassing the stock cooler...hope to see some good results.

 

syn tranny fluid will cost you more than just the high price of the fluid.
cheap dextron/mercon works better than any.

 

 

Rock On and FLT have both come in here before stating that they use a non synthetic. I use Dextron and just drain it often. I personally wouldn't do a power flush.