I run regular because most builders suggest Dex III for higher power applications, everyone I've spoke with doesn't seem to be a fan of synthetic trans fluid outside of stock setups. As for heat, I've never seen over 170 in my 80e and that was after 15 or so 1/8m passes within a 1.5 hr timeframe and never shutting the truck off.

Every combo and builder are different.

 

RPM recommends Dex3 for their transmissions. I'll stick with that.

 

I use the high temp synthetic stuff because of stall flash. Not much point in going synthetic otherwise, it gets too thin in the heat. The actual transmission temperature sits around 150 or so.

 

I was told by who I consider to be THE builder on this site when I was running a turbo 347/80E and 3600 converter to run cheap DEX 3. It was basically explained to me that the synthetics are "too slippery" in a high Hp application. If you have enough heat for that to be a concern then the cooling system needs to be addressed IMO. I could hot lap my truck in the dead of a 100deg day and never get the trans over 200 if I tried. I also had a pretty large cooler and 1/2" hoses at the time so I also had the cooling capacity. Synthetic fluids have their place but not inside a trans in a heavy vehicle behind decent power IMO....

 

I run mobil 1 dex 6 in a heavy truck with a 4000 stall and mods in sig.
after 2 seasons of abuse I had it torn apart and inspected and it looked good still.
trans temps get as hot as 185 sitting in traffic on a hot day

 

Do y'all run a trans temp gauge in the cab? If so, how?

 

My factory cluster has one, that and I log it with HPT.

 

Hmm, OK. I'll had that pid to my hpt logger and see my aftermarket options, back on topic, sorry!

 

I run a auto meter trans temp gauge. I welded a bung into the pan for the sensor.
been running it for 9 years or so and couldn't live without it

 

Good idea. I'm taking the easy way out.