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Controlling Tranny Temp

1637 Views 9 Replies 4 Participants Last post by  etk300ex
I am sure that most of you around here know this already, however, I have found that running the truck in 4th gear when towing and keeping the RPMs around 2500 makes a huge difference in the tranny temp.

I live in Arizona and on a recent trip to San Diego, I noticed this huge change. In Az, you can drive at 75 while towing, not that anyone would. That means that you can legally go at 70 mph in 4th, which gives you about 2400-2500 rpms if you are towing over 6K lbs or so. In my case, my tranny runs at around 160 degrees in very hot weather.

Now, as soon as I cross the AZ/CA border, I need to drop to 55 mph by CA law. That causes the RPMs to drop to 2100 while towing in 4th in flat. That makes the tranny run much hotter in the same weather. In my case, my tranny shoots to 185 in flats.

So, drive a little faster, keep your rpms at 2400-2500 and your tranny will run a lot cooler. In my case, I lose 1 mpg when driving [email protected] vs [email protected] My truck goes from 10.5 to 9.5 while towing 8500 lbs.

Mike
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The problem w/ the PML pan is that once it gets hot, it stays hot and it is probably harder to cool off.
More fluid is not necessarily better.
More fluid is always better. Once the fluid returns to the pan it immediately begins to cool since you are no longer asking it to do work. I agree that the cooler will work quicker to reduce the fluid temp since that is what it is designed to do while the pan is designed primarily to hold more fluid for longevity with cooling a secondary concern. I like the "belt and suspenders" approach of pairing the PML pan with an additional cooler. I'll be hauling my 6500# travel trailer up and down the I5 grapevine in a couple weeks and look forward to seeing how my just added pan/cooler combo preforms.
More fluid is always better. Once the fluid returns to the pan it immediately begins to cool since you are no longer asking it to do work. I agree that the cooler will work quicker to reduce the fluid temp since that is what it is designed to do while the pan is designed primarily to hold more fluid for longevity with cooling a secondary concern. I like the "belt and suspenders" approach of pairing the PML pan with an additional cooler. I'll be hauling my 6500# travel trailer up and down the I5 grapevine in a couple weeks and look forward to seeing how my just added pan/cooler combo preforms.
I have my results. Northbound I5 Grapevine is a very long rather steep grade that gets steeper right before the top. When last I was towing the travel trailer up Cajon Pass on I15 I towed in 3rd but near the top of the last hill my tranny temp gage still crept up to about 3/4. This time on a much longer hill I stayed in 3rd and maintained 55 to 60 mph all the way up and the gage never moved. Success!
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