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I finally was able to install a secondary transmission cooler on my 2019 Savana 3500 passenger van. That OE cooler was just not cutting it last week while towing our 35 ft travel trailer. Temps were climbing towards 220 degrees. I didn't realize that the OE cooler just "radiates the heat" by way of the small quills (for the lack of a better word). No fluid enters those quills as it only passes through the center tube. I installed a Hayden plate and fin cooler that's 11"x7.5"x.75". It should help out tremendously.
I didn't want anything bigger as we live in a northern state (Michigan) and would like warmer trans fluid temps in winter. I think this size is a good compromise for an in-line secondary cooler.
Our Alaska RV trip was ambushed this year by "you know what" so we're re-positioning our compass and heading to Mount Rushmore, Yellowstone NP, and Grand Teton NP. Only a 3 week trip vs a 2 month trip to Alaska. The Hayden cooler will still be tested.
I'll update further as we get into Wyoming and the mountains.
Edit: If installing any of the Hayden plate and fin coolers on these vans, you'll need the GM fitting (Hayden 397) if you don't want to cut the OE transmission fluid line.
OE Trans Cooler OE Trans Cooler With Hayden Secondary Cooler inline
Last edited by cjm1973; June 27th, 2020 at 1:00 AM.
I didn't realize that the OE cooler just "radiates the heat" by way of the small quills (for the lack of a better word). No fluid enters those quills as it only passes through the center tube.
That finned section of pipe is in ADDITION to the cooler which runs through the radiator (submerged - good heat transfer).
Good coolers should have a low pressure bypass. Meaning cold fluid doesn't get cooled. Torque converters generate plenty of heat so you shouldn't have any trouble getting the tranny up to temp in the winter.
[QUOTE=mountainmanjoe;449800]That finned section of pipe is in ADDITION to the cooler which runs through the radiator (submerged - good heat transfer).
Good coolers should have a low pressure bypass. Meaning cold fluid doesn't get cooled. Torque converters generate plenty of heat so you shouldn't have any trouble getting the tranny up to temp in the winter.
Unfortunately, you mounted it upside-down.
[/QUOTE
I've read that many years ago but Hayden states specifically that it can be positioned in any orientation desirable. Grant it there may (or may not) be some air for a brief second at start up. But the lines will pressurize very quickly and trans fluid will begin to move.
Out of the six aux. coolers I've installed on previous vehicles, all were installed with in and out flow ports pointing down. My Yukon ran for 130,000 miles with one before I sold it. Trans temps never jumped over 200. Great addition to the small OE cooler.
Anyway you can keep the fluid under 200 degrees is vital health for one's transmission.
OE cooler just "radiates the heat" by way of the small quills (for the lack of a better word). No fluid enters those quills
Your radiator has similar fins. You computer heat sink uses fins. Those little fins in your Hayden have no fluid. Metal is an excellent conductor of heat. Don't forget that much of the ATF cooler pipe is metal and sinks heat too.
My old vehicle had a 4L60, in rough terrain with lots of TC slip and up extremely steep hills temps would sometimes peak 250F, even with an extra plate cooler. Tranny still worked perfectly at 200k mi. I did regular changes though. Today, Dexron VI is all synthetic and withstands heat much better.
My old vehicle had a 4L60, in rough terrain with lots of TC slip and up extremely steep hills temps would sometimes peak 250F, even with an extra plate cooler. Tranny still worked perfectly at 200k mi. I did regular changes though. Today, Dexron VI is all synthetic and withstands heat much better.
I agree. Modern transmission oils are much better than of years past...part of the reason that transmission's can go much longer before maintenance is required. Heck, my Chrysler 300's tranny doesn't have a transmission maintenance schedule listed in the owner's manual. FCA calls it "lifetime" fluid. I'm personally not on-board with that one. But I digress.
Considering our van will see 90% of it's miles while towing our 7600# GVWR trailer, I'd like to mitigate excessive trans heat with the additional aux cooler. I still believe the basic principal that "heat kills". My previous TV was a 2017 Ram 2500 with the big 6.4L Hemi and the proprietary 66RFE tranny. Even climbing the Eisenhower Pass on I-70 in CO, my trans temps never exceeded 174-175 degrees. The trans cooler on that thing was stout.
If this new cooler keeps transmission temps below 200, I'll be happy. We're headed to Yellowstone and Grand Teton next month to test out the equipment. Next year, Alaska.
Three weeks ago while hauling my RV coach to a summer campground, I experienced transmission temps that approached 220 degrees. Ambient air temps were about 75 degrees. I decided to install an auxiliary trans cooler in-line with the OE. This past week, I traveled a similar route to another campground destination towing the same camper (7600# GVWR). Ambient air temps were about 90 degrees this trip. I'm happy to report a 20-25 degree reduction in transmission temps. 195 degrees is about as high as the temperature reached on my Torque app. Taking into account hotter ambient temps, this was exactly what I was looking to achieve. I didn't install a larger unit as I wanted to avoid any issues heating up the transmission during our Michigan tundra come winter. So at this point, I think our van is ready for a Yellowstone/Teton and Alaska visit.
In less than 10 months of ownership, I have:
1. Upgraded the OE shocks to KYB's
2. Added the secondary trans cooler
3. Added a rear sway bar from Hellwig
4. Upgraded the rear receiver hitch to a class V (OE was class III-IV)
5. Added a 40 amp DC to DC charger to the TV for rapid 3-stage charging of my trailer's battery bank.
6. Added mud flaps
7. Exchanged out the stock highway tires to all-terrain Cooper Discoverer Maxx tires.
8. Added a front receiver hitch
9. Added a headliner drop down DVD entertainment system for the kid's viewing pleasure
10. Added rear trailer and rear van wireless back-up cameras
11. Hardwired in a 1080p dash cam with rear/dual camera recording
12. Added a Prodigy 3 brake controller
13. Custom fit carpet-protecting heavy-duty floor liners to all the passenger areas.
14. Installed a AEM dryflow oil-less air filter.
Next two items on the agenda:
1. 1st row window tint
2. Small inverter install for the 2nd and 3rd rows.
My 2004 had leaky transmission cooler lines but no external cooler aside from the radiator. What I did was have the garage change it from a 2-line system to a 3-line system and add an external cooler. All of the hoses and cooler came from Dorman and it's all professionally hooked up and mounted which is nice. My OBDII port is dead so I don't know how my transmission temperatures are going to change...that's the last thing I need to fix on the van.
The Dorman has more pokies than the GMC but I don't know if it is more effective or not.
Transmission cooler update: I completed a 5000 mile round trip out west with the family in our van and 7600# travel trailer. This included stops in SD, CO, UT, and AZ. The rig performed exceptional over many of the high elevation passes, notably in Colorado. The highest transmission temperatures that we experienced were over Loveland and Hoosier Pass and in Custer State Park, SD. Trans temps peaked at 205 degrees on some of the multi-mile climbs when the air temps were between 80-90 degrees. But the van did better than I could have imagined. I did lockout the transmission in manual mode and held RPMs in the upper 3000 and lower 4000 range during the harshest climbs. But It was a great 4 week trip without any mechanical hiccups from the van.
The pic below was our boondocking location off the northern edge of Badlands NP.
May 27th, 2020, 9:59 PM
