Assistance needed please, Trans Fluid temp issue.

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newls1

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Good afternoon all! I have what will prob turn into a long post. Been awhile since ive posted here (couple years I think) but last time I posted I asked about swapping over to an electric fan setup to lose the fan clutch on my 2012 ram 5.7. Well, I converted to electric fan, 180t-stat, programmer to set fan turn on speeds etc... and I installed all that a few winters ago.. Ive noticed when I bought my truck (oct 2018) the trans temps never exceeded 150ish, after I did electric fan setup trans temps would go to 210 at max heat of day. programmed fan to kick in at a little lower set coolant temp and that still about the same trans temps, and Im not happy with that at all. I drove truck 2 years so far like that, and just recently put it all back to stock (minus t-stat) and trans temps still go to 18-190ish on max heat of day. What can I do to fix whatever is wrong here? Clearly im missing something or need to do something to keep my trans temp back to where it used to max at. I drained fluid and put new fluid back in, even fluid i took out was still very red and smelled just fine. New filter, all preventitive maintence stuff always performed. Just want to get my temps back in check.
 

Burla

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You should always name the transmission when you make a thread like this, rfe or 8 speed. If it is an 8 speed this is normal temp, if it is an rfe it is a little high, you in a small swing can either fix it or make it so it wont matter. Ester based fluid would be fine here, redline c+ is a proffered one and is in my rfe. I wouldnt worry what you "used" to have, as long as you are around 175f or have ester based fluid and are under 200f, your good.

As you see, you are just a hair above ideal temps.. I'd chnage the fluid and filters and then see what I have. Get a metal canister filter thread instead of oem plastic as well, oem sump filter is perfect, you you can look for synthetic options to canister filter.

transmission_failure_chart-jpg.jpg
 
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newls1

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its an rfe, and thank you foryour input sir.
 

HEMIMANN

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Ideal temp is 140 deg F for a 100,000 mile oil change interval. The higher the temp, the more frequent the oil needs changing.

I published a chart on it. For every 18 degrees F above 140 degrees F, cut the oil change interval by half. If you run 175 degrees F bulk transmission oil temp routinely, you should change every 30,000 miles.
 

steve1956

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For what it's worth. I have a used 2018 2500 with an RFE. Had 6300 miles on it when I bought it. When 1st purchased the transmission temp was always 20deg cooler than engine temp, once warmed up. Almost to the degree.
After a ride through the NC mountains one day things were hotter than "normal" for me. I wasn't sure what normal actually is, as it was still a bit new to me. I also smelled a smell I didn't like.
After reading somewhere that the OEM bypass filter was prone to failure, I installed a Mishimoto bypass filter. Since then, the temperature has never gone over 135deg. I have never used the "bypass" that comes with it. It has a thermostat that is labled 71deg-C or 160deg-F.
I now have 32K on the truck with approx. 7-8K of that pulling a 7000lb. RV.
I often wonder if the temp is too low, especially in the winter here in Delaware, as 110deg, maybe more, maybe less is not uncommon.
 

HEMIMANN

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No, it's not. Heat is the enemy of transmissions. Oil oxidizes at an exponential rate with increasing temperature. The curve is approximated by 1/2 oxidation life for every 18 degrees F above 140 degrees F. I published a data table some time back showing the trans oil change interval reductions.

Before the EPA demanded CAFE fleet standards, there were no miniscule fuel saving gizmos such as this thermostat in the transmission oil cooler lines. Any oil temp above the unrestricted oil flow to the cooler cuts your oil change interval. Get rid of the thermostat and be happy. Most of us change transmission oil every 50,000 miles WITHOUT the thermostat. With it, you're looking at 25k OCI's at most. Those that didn't burned up their RFE transmissions.
 

steve1956

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Thanks for the reply. Before the swap, if oil temp was 200, Trans was 180. etc. So after the bypass swap I figured the original was bad and was always bypassing the cooler. I still believe that since my Temps went down drastically.
Now you have me wondering if I installed the new one wrong. If the thermostat is fixed at 160 then I assume it will not open till it exceeds that temp. Would that not mean that it is now bypassing the cooler? I can't figure what changed when the valves were swapped.
In any case, what I hear from you is no problem to remove that thermostat and simply let it flow unrestricted through the cooler.
Since I bought used and had the one incident I am going to have it serviced, filters and fluid. My biggest issue is I can't find anyone that wants to do it. I can do it myself but I'm at the point I don't really want to as I don't have a lift and, well I'm getting older and it doesn't seem like much fun in my driveway.
 

HEMIMANN

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Thanks for the reply. Before the swap, if oil temp was 200, Trans was 180. etc. So after the bypass swap I figured the original was bad and was always bypassing the cooler. I still believe that since my Temps went down drastically.
Now you have me wondering if I installed the new one wrong. If the thermostat is fixed at 160 then I assume it will not open till it exceeds that temp. Would that not mean that it is now bypassing the cooler? I can't figure what changed when the valves were swapped.
In any case, what I hear from you is no problem to remove that thermostat and simply let it flow unrestricted through the cooler.
Since I bought used and had the one incident I am going to have it serviced, filters and fluid. My biggest issue is I can't find anyone that wants to do it. I can do it myself but I'm at the point I don't really want to as I don't have a lift and, well I'm getting older and it doesn't seem like much fun in my driveway.

Yeah, in one way I wish I had the ZF 8 speed tranny for improved shifting, but the service is ridiculous.
 
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