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.

[153stars]

Almost think you need in stop and go construction traffic maybe more than mountains as far as trans temp. But extra BTUs removed will aid radiator as well in mountains.

[Ted DuPuis]

Originally Posted by 153stars

Almost think you need in stop and go construction traffic maybe more than mountains as far as trans temp. But extra BTUs removed will aid radiator as well in mountains.

My observations are that the Allison produces heat most related to engine RPMs over anything else. On my most recent trip one of my coolers failed and so I went down to half capacity. It was marginal and thus gave me a much better insight into under what conditions the transmission produced the most heat.

The hottest was actually extended mountain descents under exhaust braking (which had the consistent highest RPMs. Stop and go was never an issue.

[RoadTrip2084]

Intersting. On my rig, the only time I've seen the transmission temp climb above 200f was in extended stop and go traffic situation, with high ambient temps. Never really budges on long climbs or descents.

[153stars]

Highest I seen.... my mistake I used Em/park brake and left in gear, while I dumped my tanks, five minutes or so. Torque converter slipping by to hold place, I think more of output fluid temp than overall heating. I mean less to worry about than if it was temps while pulling load or engine braking.

Originally Posted by RoadTrip2084

Intersting. On my rig, the only time I've seen the transmission temp climb above 200f was in extended stop and go traffic situation, with high ambient temps. Never really budges on long climbs or descents.

[Ted DuPuis]

Something to remember is that my setup divorces the engine cooling from the transmission cooling. In the stock setup on my Freightliner XC chassis the transmission is cooled by the engine coolant going back into the engine post radiator. In other words, you need coolant flow to cool the transmission. At idle you have low water flow because of the low engine RPM. Also since the engine isn't making much heat and the mechanical fan is flowing a lot of air, your coolant temp is probably such that the thermostats are near closed - in other words virtually no water flow through the radiator.

Incidentally, with my electric cooling fan setup, I will still run pretty cool at idle due to natural convection and just not much heat produced by the engine at idle.

My setup provides the same amount of cooling for the transmission regardless of other factors. Stop and go hasn't raised temperatures much at all in my case. But yes, the torque converter unlocked will produce more heat than it locked.

[Pudgy Camper]

Originally Posted by Ted DuPuis

Something to remember is that my setup divorces the engine cooling from the transmission cooling. In the stock setup on my Freightliner XC chassis the transmission is cooled by the engine coolant going back into the engine post radiator. In other words, you need coolant flow to cool the transmission. At idle you have low water flow because of the low engine RPM. Also since the engine isn't making much heat and the mechanical fan is flowing a lot of air, your coolant temp is probably such that the thermostats are near closed - in other words virtually no water flow through the radiator.

Incidentally, with my electric cooling fan setup, I will still run pretty cool at idle due to natural convection and just not much heat produced by the engine at idle.

My setup provides the same amount of cooling for the transmission regardless of other factors. Stop and go hasn't raised temperatures much at all in my case. But yes, the torque converter unlocked will produce more heat than it locked.

Ted your post on this mod along with your You Tube video inspired me to ditch my factory trans cooling system and add the Derale remote cooler. I recently went through my entire cooling system on my 'new to me' 04 Monaco Winsor with a Cummins 8.9/Allison 3000. I Replaced the radiator, all hoses, water pump, t-stat etc. My rig was equipped with the remote mounted heat exchanger style trans cooler that uses coolant to cool trans fluid. I've never been a fan of that style of cooler, so trashed it and had a stainless lower radiator tube fabricated to eliminate the old rusty heat exchanger. Then I mounted a Derale Hyper cool cooler and had new transmission lines built. I'm using a snap disc thermo switch on a bracket pressed up against the side of the cooler to control the fan. The snap disc switch is 160 on/ 140 off and comes on around 190, but is very inconsistent.

This weekend was the first real trip with the new cooler set up and performed ok but I think I need to tweek a few things. The hottest temp I saw was 206, but that was when we were almost home and the ambient temp was 113 here in Phoenix. Climbing the mountains up near Payson it stayed around 190 but the fan was running non stop. I have an indicator light and override switch up front on the dash so I can see when the fan comes on and over ride it with the switch if the snap disc fails or is inconsistent. I have the Derale mounted vertically on the frame in the drivers side rear corner of the coach. I'm thinking I may need to reposition the cooler to get more air flow and maybe reconsider how my snap disc is monitoring the temp.

Once I get everything dialed in, I plan to do a write up on how I did mine and post it on here with pictures and part #'s. But first I need to get it cooling better and would like for the fan to not be running 24/7. Any input on what I could do different would be much appreciated!

[Ted DuPuis]

Originally Posted by Pudgy Camper

Ted your post on this mod along with your You Tube video inspired me to ditch my factory trans cooling system and add the Derale remote cooler. I recently went through my entire cooling system on my 'new to me' 04 Monaco Winsor with a Cummins 8.9/Allison 3000. I Replaced the radiator, all hoses, water pump, t-stat etc. My rig was equipped with the remote mounted heat exchanger style trans cooler that uses coolant to cool trans fluid. I've never been a fan of that style of cooler, so trashed it and had a stainless lower radiator tube fabricated to eliminate the old rusty heat exchanger. Then I mounted a Derale Hyper cool cooler and had new transmission lines built. I'm using a snap disc thermo switch on a bracket pressed up against the side of the cooler to control the fan. The snap disc switch is 160 on/ 140 off and comes on around 190, but is very inconsistent.

This weekend was the first real trip with the new cooler set up and performed ok but I think I need to tweek a few things. The hottest temp I saw was 206, but that was when we were almost home and the ambient temp was 113 here in Phoenix. Climbing the mountains up near Payson it stayed around 190 but the fan was running non stop. I have an indicator light and override switch up front on the dash so I can see when the fan comes on and over ride it with the switch if the snap disc fails or is inconsistent. I have the Derale mounted vertically on the frame in the drivers side rear corner of the coach. I'm thinking I may need to reposition the cooler to get more air flow and maybe reconsider how my snap disc is monitoring the temp.

Once I get everything dialed in, I plan to do a write up on how I did mine and post it on here with pictures and part #'s. But first I need to get it cooling better and would like for the fan to not be running 24/7. Any input on what I could do different would be much appreciated!

I'm glad what I did inspired you to do this yourself!

From what you posted, it looks as though you did a single transmission cooler and not two, am I understanding that correctly? My setup uses two coolers run in parallel. I would recommend doing this. My experiences this summer with the single cooler showed that the fan will be running non-stop in that condition in summer temps. The rest of the year it would be fine, but if you live in Phoenix, high temperatures are a fact of life.

You could try to position the cooler such that it gets more natural airflow, and perhaps try to work a duct to help get more forced airflow. But really, I think a second cooler in parallel is the best option.

Congratulations on completing this! Did you notice any improvement in your engine cooling after the modification?