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Tranny over heating

2K views 20 replies 6 participants last post by  bigb 
#1 ·
Just changed the transmission fluid in my 01 F350 4x4 7.3L. Now the temps are running 20 degrees higher than before the change. Any ideas why this is happening?
 
#2 ·
Did you change fluid types? There have been several reports of people overheating after making the switch to Mercon V. Also, did you change the in-line filter (if you have one) or drop the pan? How much fluid did you add back? Have you checked the level with the transmission at operating temperature, engine running and tranny in park?
 
#3 ·
He pretty much covered everything lol.
Let us know what you find out
 
#5 ·
Does it have an inline filter? Did you change that? Did you get the tall filter for the pan? What brand of ATF did you use?
 
#7 ·
I can't promise that will fix this. I need you to answer a few questions. Do you have an inline filter? It will be in the rubber line coming from the cooler right behind the radiator on the passenger side. The reason I keep asking this is because if you do, and you didn't change it, it might be clogging and interrupting flow to the cooler. Also, I asked what brand atf. That's because Ford reformulated their ATF, but you might have gotten some of the old stuff. I personally won't use Mercon V, but Mark the Ford tranny guru recommends it. You just have to think if you did x, and then y happened, it has to be related.


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#9 ·
Did the oring come out with the old filter in the pan? Sometimes they stay up in the tranny and can put the new filter in with it still in there and will cause issues.
 
#11 ·
What exactly are the temps you are running?
 
#13 ·
If you are talking Fahrenheit your tranny isn't even reaching operating temperature. Ideal temps for these are 170-180 and they can run 200 all day.
 
#14 ·
A clutch isn't slipping. If it were the clutch would be destroyed in a couple miles.

The temperature rising from 119F to 150F is a non issue. A difference in ambient temps, traffic, wind direction, etc, can cause this. I think this thread is an exercise in trying to fix something that isn't broken.
 
#16 ·
OK, have it your way.

That's odd! Let's get this fixed. First thing, change the bypass on the side of the trans. It could be leaking. If that doesn't do it, try new coolers. Maybe they got some debris and are restricted. If those two don't fix it I recommend a new transmission.
 
#17 ·
I don't see my previous post. Maybe the censors got it.

Mark - aside from the torque converter - what generates heat in a transmission? Clutch slipping is out as per your previous post. The torque converter didn't change. As I said in my ghost post, I doubt Mercon V has such a different fluid characteristics as to affect energy transfer in the torque converter. Heat would seem to be produced only with energy loss - friction, conversion inefficiency, etc. Just curious where the heat comes from after the torque converter locks up.
 
#18 ·
There is very little heat generation in the transmission once the converter is locked. There is some heat from each upshift. Downshifts in a 4R100 just release a clutch, and that generates very little heat.

If the converter isn't locking in fourth gear in this case that will generate higher temperatures, but I'd expect quite a bit more than a 20F increase.
 
#19 ·
So, it looks like once you got on the highway, torque converter locked up and going a steady speed, that the transmission should cool down close to the temperature in the bottom of the radiator. Yet, mine never "cools down" - it seems like once it hits its steady state, it stays there no matter what I'm doing - towing heavy in stop and go or cruising on the highway. It would seem there is some heat source even with the TQ locked up. Maybe the pump? There's a lot of fluid churning going on there. Just wondering.
 
#20 ·
The pump will generate some heat. Nowhere near what an unlocked converter can generate. Also, meshing gears generate heat. In overdrive there is a 0.71:1 ratio, so that's generating some heat. Bearings and bushings generate heat, too.

Once the converter is locked a valve moves in the valve body that reduces the flow to the cooler because the heat generation is down. Overcooling the trans isn't good, either.
 
#21 · (Edited)
When I first installed my 6.0 cooler I didn't have a thermostat in the line. My temps varied a lot with no real rhyme or reason. Sometimes they would run 130, other times 150,160,170. Sure hot days made it run hotter and highway speeds too on average but there were so many variables it would not be easy to try and figure it out. Once I installed the Derale stat the temps evened out to almost a predictable average depending somewhat on load and road speed, city and highway driving. However no matter the load or speed it does seem to settle in after it fully warms up and stays at 190-200 Winter or Summer doesn't make much of a difference.
 
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