Hey guys about 2 years ago I had high trans temp while not towing and it was during the winter months. It turned out to be a bad trans cooler bypass valve, once that was replaced everything was perfect. Now while not towing I am noticing shes running hot again. I already have the 26 row cooler installed and also a trans filter from Dieselsite. I can easily hit 200 no problem. I decided to pick up another bypass valve and try that. It worked great for one day and wouldnt go above 150. Today on my way home I am seeing it at 180 which under normal conditions I never saw about 160 or so even during the summer. Today in Jeresey its about 70 with rain so its not screaming hot.

To add to this I towed 2 weeks ago to PA, I pulled a trailer with a Dodge Dakota for about 3 hrs and the trans got to 245 while in a tow tune from my DP tuner. I had the truck sit for a while after I arrived and than we loaded up a full 4door F250 and towed that back, it didnt reach as high as before but still wasnt in my comfort zone. Could I have damaged the trans and now she is going to run hot all the time? The fluid is about a year old while maybe 20k on it.

If you need more info just ask,
-AJ

 

You call your trans filter a bypass type in your signature. Does that mean the filter is not in the line going to the cooler? Cause the more common filter is not a bypass type and is in line with the cooler/s. As there is usually not a bypass valve in these filters, a clogged filter will over time block the cooler/s.
Larry

 

I never realized I put that in my signiture like that. I do appologize its just a trans filter from dieselsite. The bypass valve i am talking about is on the side of the trans that the cooler lines tie into. I was told before its like a t stat for the trans. As it gets to a certain temp it opens allowing flow to the cooler.

 

It's time to run a flow test.

1. Get two containers, each at least a gallon. Get a friend to help.

2. Warm up the trans.

3. Remove the cooler line where it attaches to the rear of the trans. Point the line into the first container.

4. Have your friend start the engine, leaving it at idle in park.

5. As soon as the flow is steady (should only be 2-3 seconds) move the line to the second container. NOTE: If there is fluid spraying out of the transmission SHUT THE ENGINE OFF. This indicates the test has failed. A small drip, or even a few drips out of the trans is normal.

6. Keep the line in the second container for EXACTLY 15 seconds, then move it back to the first container and shut the engine off.

7. If there is at least one quart in the second container it passes and the flow is normal. If there is less than a quart, or there was a spray coming from the trans it fails the flow test.

A failed test means one of three things.

a. There is a restriction in the cooler circuit. This could be a damaged/kinked/pinched hose, debris in one or both coolers, or a damaged cooler.

b. The bypass valve on the side of the trans has failed. Rebuild kits are available. They are inexpensive and easy to install.

c. The pump is worn out. This is not very common, but it can happen.

Some people say a plugged internal filter can cause this. I disagree. If the internal filter is plugged you have MUCH bigger problems than high temperature. The only way the internal filter can get plugged is if the transmission has failed.

 

In my post I was referring to an additional external filter which I assumed was the type that AJ referred to in his signature.
Larry

 

You can't get better advice from anyone else than Mark when it comes to this trans so I would do as he suggests. My guess would be you may be failing that test but I hope not. As far as the bypass goes, mine was removed by John Woods when he did my trans. He just puts spacers in place of the bypass.

I have the 6.0 cooler and can't get my trans over 180 no matter what I do. I was just on a 2500 mile trip pulling my 34' 5th wheel trailer and pulled a step grade for several miles, the trans didn't go over 180. My oil temp got up to 243 degrees though so that can tell you how much load was on everything. The temp outside was around 104 at the time also. Normal temp going down the road runs about 165 so pulling a step grade only raises it about 15 degrees for me.

Best of luck and hope you find something simple!

 

That's incorrect.

The bypass only works on pressure, not temperature. In normal conditions it is always 100% closed, with 100% of the flow going to the coolers. If the cooling circuit gets restricted from a damaged line or a clogged cooler, it opens to maintain flow. The return from the coolers is used to lube the rear half of the trans. If there was no bypass and a problem with the cooler circuit there would be no lube to the rear of the trans. The life of the trans would be measured in feet, not miles.