I have approximately 31k miles on my 3500 passenger van now, most of which are extreme duty miles for towing my 7500# travel trailer.

We have some big RV trips planned this summer and in the fall, probably tacking on another 15K miles.

First, would it be good practice to at least change out the trans fluid before these miles? I think I read in the owners manual that 37,500 miles is the interval for trans fluid and filter change for extreme duty. I'd rather be conservative as the next 15 miles will be taxing on the powertrain (mountain grades).

Secondly, should I stay with GMs AC Delco Dexron VI fluid or would a product from Valvoline (Maxlife full synthetic ATF Dexron VI compatible) be a good substitute?

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oil that meets the Dexron VI spec must be synthetic. Nothing wrong with the Delco. The Valvoline is probably exactly the same.

Manual states that severe duty change interval for ATF is 45k miles, so doing it now would be about 30% early. ATF is really expensive. It's up to you.

All the mountain grades will punish the fluid, so personally I would change it after not before.

 

I believe all ATF Dexron VI is synthetic, but I use the Valvoline Dex VI in my vehicle. I think your use justifies the expense of a Dexron VI fluid and filter change. If your van doesn't have an air cooler for the fluid, I would add that, as overheating the transmission is why so many go out early..

 

i have a secondary auxiliary cooler installed in-line of the OEMs. I haven't seen temps over 195 degrees, even towing up a grade in hot weather. The transmission performs flawlessly and I'm wanting to keep it that way. That's why I think a fluid change is warranted.

 

Agreed on the fluid change. I commented today on your old post about the cooler you added. And based on my experience changing my own trans fluid and filter at 31,000 in my 2019, I would definitely change your fluid. I gather that most of those miles were prior to you installing the cooler.

When I changed my fluid at 31,000 the fluid was reddish brown and while there was not excessive clutch material in the pan, I changed the fluid anyway due to the unknown use in the van's previous life. I used Maxlife as its easy to find and meets the Dexron VI spec. Now that I have seen how the trans temps behave with only the OEM cooler and towing a heavy travel trailer, I will be adding another trans cooler and doing a complete fluid exchange using the MAXLIFE ATF prior to my trip to SD and the badlands. When I changed the filter a few months ago, I only replaced about 6 qts so installing the cooler will be a great time to do a fluid exchange.