Transmission oil pre-cooler

[JMalik]

I have noticed over the years that as I am climbing hill in the western states mountains that my engine output collapses with the increased hill climbing load. I finally decided that the problem was associated with the placement of the transmission cooler in front of the end stage of the engine inter-cooler. Thus as hills are encountered and the transmission generates more heat that in turn is ends up dumping more heat into the OEM oil cooler which then dumps the heat into the inter-cooler. The 12 valve Cummins diesel is very sensitive to intake air temperature. The engine output drops dramatically as the intake air temperature climbs. I went on the Internet to try and find out what the BTU rating of the OEM oil cooler was with no luck. So I decided that the best approach was to introduce a pre-cooler in front of the OEM transmission oil cooler. I welded up some brackets which allowed me to install a Setrab SLM592-10 33,000 to 46,000 BTU (with 60 mph airflow) oil cooler in the inner space behind the bumper below the OEM cooler. This has helped my engine output. However, the air flow is not optimal and I added supplemental fans to try and increase the flow of air through the cooler as a partial solution. I would like to just remove the OEM cooler but with no data on performance that’s not a great move.

Is there anyone out there who has worked the “OEM oil cooler problem” on the second generation Dodge and come up with a better solution for working this problem.

 

[JMalik]

I installed an ISSPRO R17599 100 to 280 deg F transmission temperature gage to gather information on how my pre-cooler is performing. A 25 mile run at mostly 70 mph yielded a maximum 130 deg F with Pyrometer reading 800 deg F peak and boost of 6 psi on a moderate hill climb of about 1 mile. In our local town out of converter lock and in automatic mode the 47RE transmission oil eventually rose to 145 degrees F. Sitting and idling in static air with only fans pulling air through the oil coolers seemed to be the worst case condition for raising transmission oil temperature.

The ISSPRO Transmission temperature sensor was installed in the provided threaded position on the back side of the MagHytec 727-DD. The Setrab SLM592-10 transmission pre-cooler had 2 centrally located SPAL 30103009 fans in suction mode provided 200 m2/h airflow running at 2.3 amps each at 12 VDC. This run was in the high desert at 2200 ft with an ambient temperature of 60 deg F.

What are the operating temperatures for a 2nd generation 12 valve under normal operating conditions? Would appreciate some information

 

[JMalik]

Here is a picture of the installation;

 

[Joe Mc]

More capacity nets better cooling as well as additional coolers. I wouldn't recommend eliminating the block-side cooler as this does aid in reducing temperature but it also helps warm up the fluid in the winter months. Consider a Mag-HyTech (or other manu) double-deep pan. I forget what the stock pan nets in total fluid capacity but do know that with the DD Mag-HyTech pan a fluid change (including draining the converter), including 1 oz. Lubgard Red/quart of fluid, takes 4 gal + 1 qt. I've seen some guys install large coolers with fans "in the front of the bed of their trucks" and took notice they also installed by-pass valves for winter ops.

 

[JMalik]

The bypass valve sounds like a good idea considering the low running temperatures that the transmission oil gage shows. Improved Racing's FSM-145/165 bypass valve looks like it should do the job nicely and pull the heat load from the intercooler as it bypasses the OEM transmission oil cooler. Running at 165 degrees F the valve will crack at 160 degrees F and be full open at 181 degrees F.

 

[Joe Mc]

I recently moved the trans temp sensor from the Mag-HyTech DD pan bung and installed an in-line Tee (forget where I got it?) one the trans out to the block-side cooler in line. Recommended installation is in this line for a better idea of what the trans temp(s) actually are versus what's going on in the pan = after fluid is cooled. With new set-up and not hauling anything typical temp is 105* running down the hi way at 70-80 and or usually any speed above 40. I'll notice that while driving around town (stop and go) the temp will come up to about 140-145. I'm very pleased with these readings and confident in the "stock" cooling at least for my situation.

Prior to relocating the sensor from the pan. In Nov. 2017, I helped relocate our daughter from home (Levittown, PA) to Marysville, WA (Seattle area) round trip about 3000 miles. With the bed of the truck packed (under hard cover roughly 1000#), back of the cab packed to the seat back window height (roughly 500#), her car (02 Merc. Sable = 3500#) packed to the belt-line (including trunk figure another 700#) on a U-Haul Auto-Transporter (2210#) = all together (not including she, me or truck weight) we were hauling around 8000#. Driving on the open hi ways (of course ambient temps much lower in the winter months) the temp never exceeded 110*, in-town never higher than 150* and much to my surprise as we pulled the Snoqualmie Pass (WA) at the posted speed limit of 70 the temp maintained 105*.

Above is just for reference of temps and conditions.

 

[JMalik]

My following results correlate with Joe Mc's measurements above. On converter lockup the temperatures generated by the transmission are minimal. Transmission temperature surges are mostly experienced out of converter lockup with the converter operating at full capacity.

Feb 15, 2019

I went to Harbor Freight and picked up an AMES InfraRed thermometer so I could do spot temperature checks. After a short 25 mile run at 65 mph and local town speeds my ISSPRO gage monitoring the transmission HD Mag-Hytec pan was at 130 degree F which correlated with the IR thermometer. The SETRAB cooler input end cap was 170 degree F and the output was 150 degree F. With and ambient 43 degrees F the transmission oil temperatures seemed to change pretty fast as I checked them with the truck transmission in park and idling.

I found that the IR thermometer laser spot had to be carefully positioned in the center of the cooler input flow path to get an accurate reading of maximum input oil temperature. Temperatures rapidly changed on either side of the flow path center. A similar condition existed on the Mag-Hytec oil pan with the ISSPRO gage temperature sensor readings at the sensor position correlated with the gage those away from the sensor did not.

On a trip out of town, running into our high desert wind resulted in 8 psi intake manifold boost for 70 miles. At 70 MPH I experienced 100 to 107 degrees F indicated oil temperature. SETRAB cooler input was 144 degrees F on its end cap. The return trip with a following wind the boost was 3 psi and Temperatures ran around 110 to 120 degrees F. The SETRAB cooler input was 155 degrees F measured on its end cap. During these extended runs the 47RE transmission converter was locked up and the transmission was in overdrive. The ambient temperature was 50 degrees at 2200 to 3500 feet altitude.

With the transmission converter unlocked and running on local streets the indicated gage temperature was 130 degrees F.

Feb 18, 2019

I installed the Improved Racing FMS-165 bypass valve across the input to the OEM transmission oil cooler. I also installed a 160 degree F thermostat at the output of the transmission oil outlet in an inline fitting. The next day I raised the transmission pan oil temperatures to 130 degrees F with local driving resulting in the Setrab fans being activated with the 160 degree thermostat. The Setrab oil cooler measured input temperature was 163 degrees F and the output was 134 degrees F.

As designed the Improved Racing’s FMS-165 bypass valve allows no more than 10% of the Setrab oil cooler output to flow through the OEM oil cooler at its maximum 20 GPM flow rate. The pressure differential across the bypass valve results in the flow through the open in/out ports of the OEM cooler. Once the bypass valve reaches 160 degrees F it will then proportionally turn off the bypass with full bypass closure at 181 degrees F bringing the OEM cooler completely on line.

 

[JMcCoy]

Lots of good information here. It sounds like you have your issue licked. Also inefficient torque converters can create a lot of heat. Although this should not be a factor while locked up, assuming it's not slipping. ATS makes a cooler that looks pretty good. I was considering it when I replaced my transmission, but thus far heat has not been an issue for me. Of course, I have not been out to the Rockies.

 

[Joe Mc]

Correction on miles round trip 5,750

 

[JMalik]

3/18/2019: On a 250 mile trip including the Tehachapi, CA 404 ft to 3970 ft grade I note the following.

Level travel @ 2000 ft to 4000 ft Pan temp 130 to 140 degrees F ambient temp 55 degrees F
Tehachapi 15 mile grade from 404 ft to 3970 ft Pan temp 150 degrees F ambient temp 55 to 75 degrees F

Estimated transmission oil output temperature temperature with a 20 degree offset with Setrab precooler is
Level travel 160 degrees F
Hill climbing 170 degrees F

The bypass valve starts opening at 160 degrees F with full on at 181 degrees F. The oil on the down side of the precooler is at the pan temperature which peaked at 150 degrees F so on this trip the OEM cooler was not on line.

 

[JMalik]

In response to J Mcoy: I considered the square coolers with fans but the available space was not very compatible with this form factor. I settled on the Setrab SLM592-10 33,000 to 46,000 BTU cooler because it fit my available space behind the bumper. I also added 2 fans to get the air moving through the Setrab cooler.

On converters: I agree the OEM transmission converter is not very efficient and I have been running a Transtar S3 multi clutch converter with a stall at 1900 to 2300 rpm which is more in my engine's operating range with a 3.54 differential ratio.