Out Jeep WJ 4.7 V8 has the auxiliary transmission oil cooler for the 45RFE transmission , which suits us because we regularly use it to move a heavy trailer. During the last overhaul of the cooling system I would have liked to replace it – but I wasn’t able to get a spare part. So the original one was still in place while I was still looking for a solution. Indeed, the connection from the radiator to the auxiliary oil cooler seemed to be leaking, what I wanted to fix in the winter break. But when restarting the Jeep after the break it turned out that – at least now – it wasn’t the connection leaking, but one line of the auxiliary oil cooler was broken and a lot of ATF was leaking there (see pictures below).
As the main inspection at german TÜV was overdue, urgent replacement was needed. I didn’t want to install a used cooler as I would expect a similar problem as with the original one soon. So I started looking for a fitting universal oil cooler. No dealer offered a fitting universal part (indeed, space is quite tight). At the end I was able to find Mishimoto oil cooler which I was able to fit into the tight space.
Used parts and tools
- Mishimoto universal transmision oil cooler 305x190x19 mm
- BAT Motorsport 90° block angle DASH 6 / -6AN JIC 6 inner thread
- BAT Motorsport aluminum fitting for pipes 9.5 mm
- BAT Motorsport hose push on adapter 10 mm
- HAZET pipe cutter small version (item number 2181N-1)
I can’t guarantee that the fitting and hose sized mentioned here are suitable for all Jeep WJ’s. Please check the sizes yourself!
Removal of the defective transmission fluid cooler
The first challenge was removing the defective transmission fluid cooler. This time I didn’t want to remove radiator and air condition condenser because both still have been filled. Also, the union nuts of the fluid lines at the auxiliary oil cooler were stuck, so I wasn’t able to remove the lines there. If the radiator is removed, the oil cooler can removed with the lines on it but with the radiator installed the space besides the radiator was to small to get the lines through. Finally, I was able to remove it with the help of the HAZET pipe cutter: I was able to cut both lines besides the radiator and the auxiliary oil cooler could be removed. The picture below show the cut lines of the auxiliary oil cooler with the pipe fitting already installed at the inlet pipe.
Installing the Mishimoto universal transmission oil cooler
First challenge with the Mishimoto universal transmission oil cooler: It’s much wider than the original one and extends behind the struts for the hood lock. At my WJ, ist just fitting between the struts and the A/C condenser (but the cooler could also be to thick for other WJ’s). The picture below shows how it finally fit into place. While making it fit I had some failures due to the tight space which I’ll quickly describe below to avoid falling into the same traps again.
In the first attempt, everything looked easy: The old transmission oil cooler is mounted in front of the A/C condenser using a strut. I drilled out the rivets of the original transmission oil cooler (below left), drilled two new holes for the Mishimoto cooler and screwed in. Looked perfect as you can see below right! Until I started installing the struts of the hood lock and realized that they don’t fit any longer. Next try was using the original installation material delivered with the Mishimoto cooler. Mybe with the A/C condenser removed it would have worked…after fumbling for a while I stopped it because I wasn’t able to fix the oil cooler, so I had to find other means for installation.
At the end it worked using the following combination: On top the cooler is fixed to the strut using cable ties (picture below). At the bottom it is tied to the A/C condensor, also using cable ties. The original installation material stayed as best as possible. Tip: Install the outlet hose and clamp before fitting the oil cooler in place, because then it becomes pretty tight (picture right).
Because the original outlet pipe was a bit loose held only by one clamp without being screwed to the cooler, I completely replaced it using the Mishimoto hose (picture below left). The input was a bit more difficult: I didn’t find a fitting with matching size/thread for the original transmission fluid outlet of the main radiator. So I installed a pipe fitting on the cut original line, adding a 90° angle and a hose fitting, from which I connected to the oil cooler using the Mishimoto hose. The 90° because else the hose would be kinked. The installation can be seen on the picture below right.
Result
Some time passed between the installation of the Mishimoto transmission oil cooler, the original article and the translation (still doing it manually myself!). In between, the Jeep was used for two summer seasons (about 1,5 years real time) and everything seems to work fine.