I have the tranny lines going to radiator than to factory tranny cooler.I was going to cut hard lines closer near radiator and use the fittings that go onto hard lines adapt to 6an run to cooler.SHOULD i bypass the radiator.sum guys do say it should keep cooler cuz not running threw hot radiator?Also what fittings are the ones that go into to true cool that are 6an.There inverted flare i read but sum guys say they bottom out sum cut the cooler alot of mixed opinions.want fittings the screw into bottom of true cool to -6an.

 

You're going to get a lot of mixed answers on this. The subject has been debated for years.

Every aux trans cooler I've ever installed on my own vehicles, and on customer vehicles, have ran through the radiator first. In 22 years, I had ONE factory cooler in the radiator that ruptured. Made a nasty mess of the cooling system, but was repairable with a few hours of extra work. That particular vehicle was 14 years old with 180K on the odometer.

That's one vehicle out of thousands.

 

If i use kooler klean in a aerosol can and use air after will that clean my radiator cooler gd..i could just flip the line 180 than like every one does buy fittings from napa that snap in factory hard line and screw into the 40 k and done

 

The only factory coolers I would bypass come on Nissan vehicles. They have a tendency to rupture and it takes out the TCM in the valvebody.

As for your cooler question, this is what I like to do. The hot fluid coming from the transmission I first feed to the lower fitting of the radiator, the top line becomes the output to the auxiliary cooler, I like using Derale coolers with a built-in 8" fan. I put the temperature switch in the outlet fitting of the auxiliary cooler. If the fluid returning to the transmission exceeds 175*F the fan activates. Works very well for me with my 4L80E in my Express van. The fluid in the pan stays under 180*F year round. Several companies make a thermostatic bypass valves to divert fluid straight back to the transmission should it be operated in cold weather. I briefly considered adding one, but came to the realization I mainly drive the Express in warmer, summer months and usually on long trips with a trailer so the expense was not justifiable.