External Allison Transmission Cooler Setup

[Ted DuPuis]

Originally Posted by jdkskyking

I’m just getting up to speed on your mods. I’ve got a C13 mated to Allison 4000. Cooling the transmission is typical, completed in the engine radiator. The Cat runs warm, why aggravate the situation by trying to cool transmission.
My rig is capable of upwards +60k lbs when towing.
I’m interested to know if Derale assisted in selecting your coolers setup?
Thanks.

Derale wasn't involved in selecting the cooler setup. With two coolers I think my setup is oversized for my Allison 3000 in my bus which maxes out around 30k. It might prove sufficient for your 4000 behind a C13. I think realistically I oculd run my setup on a single cooler if I ran the fan all the time and mounted the coolers vertically. As it is my coolers are mounted horizontally (so very little natural airflow) and the fans barely run.

[JonathonM]

Ted,
Just saw this thread and your YT channel (lots of good information).
I recently purchased a MH and had this experience: https://www.irv2.com/forums/f22/auxi...ml#post6506218
MH has 16k miles. I recently changed the filter and drained/filled fluid in the pan.

What are your thoughts?
Any suggestions for which cooler size and type i should go with?

[Ted DuPuis]

Originally Posted by JonathonM

Ted,
Just saw this thread and your YT channel (lots of good information).
I recently purchased a MH and had this experience: https://www.irv2.com/forums/f22/auxi...ml#post6506218
MH has 16k miles. I recently changed the filter and drained/filled fluid in the pan.

What are your thoughts?
Any suggestions for which cooler size and type i should go with?

I'm not particularly familiar with the W20 chassis yours has, but I am assuming it's a GM gasser?

Regardless, my thought is that I would add one of the coolers that I put two of on my bus, and put in the in-line thermostatic switch I used as well (which is 180F on, 165F off). For the routing, I would have fluid go from the transmission, into the auxiliary cooler, and then to the radiator, back to the transmission. What's nice about this setup is that with it, both the radiator and transmission cooling circuits have the ability to help the other one out, depending on which one is in need of a bit more help.

If you go to the video on what I did from my channel (Titled: "Adding an Independent Transmission Cooler Setup for the Allison 3000 on my RV"), I've got Amazon links to the parts that I used, including the relays. You can buy cheap China relays for much less than a good Bosch one, but the Bosch one is going to be higher quality and something you can depend on. What's nice with this fan setup is that you can mount it anywhere, at any angle, and the fan forcing the airflow will still keep everything cool.

I've become a huge fan of these Derale coolers, and used one also for my separate oil cooler I added to the bus. The things just work really well and have proven trouble-free over the now several years and tens of thousands of miles I've been using them.

[jacwjames]

Ted,
When you post something I take the time to read it, very interesting stuff.


I had to have my radiator replace in 2015, road debris took it out. Had a new installed and only used the rig for one long trip in 2015 and remember a transmission high temp alarm on my Silverleaf but attributed to a long grade I was climbing, downshifted to increase RPMs and temp went down


Fast forward to 2021 and took a ~7K mile 6 week trip and had multiple high temp alarms with the worse ones being in stop and go city traffic. Checked some things, did an oil analysis, and even checked the cooler inside the radiator to make sure there were no obstructions. Took another trip and had more high time. Called the radiator manufacturer to ask how the sized the internal cooler and they couldn't tell me but offered to sell me a $750 add on cooler.

So I bit the bullet last year and installed a Derale cooler in series to the internal radiator cooler. Works great.


My wife just got back from a trip from Knoxville to Ashville through the mountains. I had set up data tracking on my Silverleaf and checked it and the tranny temp never once exceeded the engine temp. I could tell when she was pulling hills as I tracked to boost pressure too. Worked great.



NOW my question, did you check with Allison as to the option of an add on cooler??? Another Monaco owner with a 4000 transmission wanted on installed and the Allison shop refused to do it, saying to much back pressure!!

[Ted DuPuis]

Originally Posted by jacwjames

Ted,
When you post something I take the time to read it, very interesting stuff.

Thank you! I really do appreciate comments like this - it's nice to know that what I'm doing helps others.

NOW my question, did you check with Allison as to the option of an add on cooler??? Another Monaco owner with a 4000 transmission wanted on installed and the Allison shop refused to do it, saying to much back pressure!!

I didn't consult Allison on this one and instead tried to make sure I was sizing things such that I wasn't creating a significantly increased restriction that would cause problems, as too much backpressure was a scenario I was concerned about.

The one note I'd make on my system is that the hose shop I went to ended up using a smaller ID hose than I would've wanted, and I should've complained to them about that and had them redo the hoses. I had -12 fittings but they used 5/8" ID hose (which would normally be -10). That said, it's been about 2 years (so roughly 20k miles) since I installed this setup, and the transmission hasn't given me any hints that it's unhappy. Occasionally it will slip when it upshifts between gears but it did that before (probably moreso) and in the >30k miles we've put on it and roughly 118k total miles, it's still behaving very well. It overall shifts smoother and happier, and my trans temp never exceeds 200F.

When sizing hoses and fittings, you rarely can go too large, but too small absolutely will be a problem. I still wish they'd done 3/4" (proper -12) hose instead of 5/8", but again, it hasn't concerned me. Maybe one day if I'm out of things to do or can find another use for that long hose from the transmission to the coolers I'll get new hoses made up, but it's not high on the list.

[jacwjames]

I did make sure to use #12 hose and fittings. I was aware of potential for back pressure but didn't try to install a gauge.

So far I am satisfied. The Derale is doing it's job and the transmission temps are considerably (~50 F) cooler. Can't beat that.

[Ted DuPuis]

Sounds like you got it set up just fine then. Heat will kill transmissions quickly, the under sizing I see from factory is crazy.