Aztec4x4 Transmission Cooler
Hi all, I thought I'd post up the transmission cooler I have had fitted to my 2010 JKU CRD Auto.
My thoughts on temperatures are that engines should run in the 80-90defC range and auto transmissions in the 160-180degF range. I am also aware that a transmission shouldn’t be ‘over-cooled’
The 545rfe transmission actually has a very high safe operating temperature which is a good thing. However, placing a scorching hot transmission cooler in front of the main engine radiator was a poor choice by Jeep (for the hotter climates anyway). Having the transmission share a panel with the AC system was also a poor choice.
As most of us know, these CRDs like to get a bit hot now and then....mine also has ridiculously heavy 35s on it, and all the bar work, winch, dual battery etc. So mine’s probably a worse case scenario (towing would also sit high up the danger list, but with the TC locked up and running above 80km/h the transmission cooler should be getting plenty of air).
The main thought process was to move the the transmission heat away from the engine radiator. I'd take a hot gearbox over a hot engine any day.
The solution Aztec4x4 has installed for me includes a thick laser cut steel bash plate, designed in a way that it doesn’t sit any lower than the chasis cross member. The bash plate acts as the mount for the transmission cooler.
The cooling panel is basically the largest that would fit in the space created. This cooler now works in isolation, we didn’t route the fluid through the original cooler.
After an initial install, I did a good test run in reasonable temperatures (30ish). The transmission sat about 165degF when at freeway speeds. This is a perfect temperature for the transmission and indicated the cooler was the right size.
I also did a test where i found the steepest hilly suburb I could. I drove around accelerating hard up the hills for a while, churning up the transmission fluid. The transmission temp rose and rose but stabilised at 215degF/100degC. This hotter than I would want to run at usually, but quite acceptable as a worse case. For reference, the 545RFE is safe up to 240degF.
My issue with the 545RFE is that it never seems to lock up at around 70km/h. So stop start driving creates a build up of significant heat. This is of course, still the case with the new cooler. But I have the option of using the OD off button on very hot days. (OD off is great for up to 80km/h in my Jeep and encourages TC lock up) The main thing is that even if the transmission gets very hot, the heat bypasses the engine radiator so i have a lot less to worry about.
Another thing I noticed is that now, because the trans cooler is away from the main engine fan, it gets limited air at crawl speeds. I never got it anywhere near close to dangerous temps but I thought it would be a good idea to have a selectable fan installed to switch on if I’m rock crawling for example.
After the install, engine temps are usually in the low 80degC’s which I’m happy with, the transmission stabilises at 160-170degF last time I was on a long highway run, and it reaches around 190degF on hot days doing city driving (If I use the OD off button the transmission will stay under 170degF in the city). I will continue to monitor temperatures through summer, but I think it will be fine.
The cooling fans work nicely at crawl speeds, and I could always switch them on in traffic if i needed.
Any questions, post them here.
Sam
|
