[speediq99]

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

 

[RobKar]

Well, that is why I run a PML tranny pan

 

[speediq99]

I am not sure that the PML by itself did the trick for me.
I had to add an external tranny cooler to see a difference.

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.

Mike

 

[speediq99]

To elaborate a bit more on the PML pan and in my experience, the pan keeps the tranny running cooler under normal driving.
When towing and pushing 3rd and 2nd gear, the tranny fluid will heat up. Under these conditions, a lot of hot fluid may not be necessarily easier to cool and a tranny cooler seems to make a big difference.

Day-to-day driving with light towing, either a PML pan or tranny cooler is all you need. If I had to do it over again, I would do a tranny cooler first and the pan second if needed.


Mike

 

[RobKar]

Looking at the benefits of both, you get slightly more with a big tranny cooler. However, the performance of the radiator will suffer with a big tranny cooler in the way. I went with the CMS radiator, All aluminum double core, and the PML pan. Having more fluid over a bigger area will help substantially. Also, the fluid will last longer.

 

[typerr]

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.

 

[RobKar]

When you say :spam: you say it all

 

[typerr]

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!

 

[speediq99]

It sounds like the PML/cooler combo worked for you.

You may want to get a tranny temp gauge rather than use the one from the truck. in my experience, these gauges stay in the 1/2 way mark or below for a long time (long temp range). Once you reach a certain temp, the difference between a visual half way mark and near the H mark is 3-5 degrees.

If you manage to stay in 3rd gear, all is usually well. It is when you have to do 2nd gear that things begin to fall apart. My truck does not like to stay in second for very long, water and tranny temps quickly jump up.

Mike

 

[etk300ex]

More fluid is always better.

Absolutely positively!