DIY Trans Cooler for ~$300

Thanks for this write up. I'm doing a drain & fill this weekend to get me by for a while until I can assemble the parts. My truck is a 2021 with 32k miles on it so it's time for a drain & fill anyways. I plan on adding a trans cooler, before winter if I can squeeze it in but more likely after winter.

I just moved to the North Carolina High Country near Beech Mountain. So, we now drive winding mountain roads every day where we're often running slow speeds.

After a week or two of being up here, I started to notice a slight "burnt" smell when we'd get home occasionally. I'd most notice it between the cab & the bed. Checked everything underneath once it cooled off and couldn't find anything, so I figured it was a fluid getting hot.

We often have to use 4H to get up to our house. From the entrance to our neighborhood, it's 1.7 mile drive up a gravel road but it's nearly a 2000' elevation change. Though the road is well maintained by our POA, there are several tight switchbacks, and I use 4H often on those. Especially after a rain. I imagine I'll be using 4H all the time in winter.

Started monitoring my trans temps via the OBD Fusion app with the Veepeak BLE OBDII adapter. Sure enough...trans temps were running upwards of 235-240. Hottest I saw coming up the mountain was 252 on trans temp sensor #2, which I assume is the return line. That hotter temp was in 4H, but no towing. Ambient temps in the low 70's. I'm planning on buying a small UTV/side-by-side in the future. I dread the thought of what the trans temps will look like towing a (small, but loaded) trailer up to the house.

Drain and fill now. DIY trans cooler coming soon.

 

I remember reading some discussion somewhere on the forum about long slow speed inclines are better to use 4LO to keep trans temps lower, maybe try that to see if it helps your temps.

 

That's nearly a 22% grade. About the same as my driveway which is ~ 500' long and I see rapid TC temp rise.

 

Slow speeds on an external cooler could Really use a fan. I'd recommend adding one over the cooler using a 5pin relay and a dash mounted override switch for when not needed. Pinned and with fan on- the highest I see is now low 200s for very brief periods (I used to see 248 for extended periods) under the most severe situations (repeated stop/go at over 105 ambient) - while cruising at 75 = 170. You'll have much longer fluid change intervals saving some money there. Luck and enjoy the new area.

 

Good call. Our "speed limit" in the neighborhood is 20 mph, though there's no way 90% of vehicles get close to that on some of the steeper grades. 4L should be fine at those speeds. There are 2 Subarus (I think they're WRXs) and 1 Porsche owner that love to speed up the mountain like they're in the Pikes Peak Hill Climb race. I don't mind holding them up when they're behind me. lol. I don't know why I didn't think of just going to 4L in the first place.

Solid advice. I wired a supplemental electrical fan on the radiator in my XJ (they're notorious for poor cooling).

 

I like this setup for a trans cooler. I've contemplated doing it so I bought a OBD bluetooth to monitor temps. I have a 39 mile drive to work that is mostly highway with maybe 10 miles of 45-55mph roads that are up and down hills and a little town driving. Highest I normally see with mid 80's ambient temp is 210 degrees. Converter will creep close to 220 if i'm really sitting in traffic or traffic light. As soon as I get moving, temps drop back down. Without driving pikes peak or towing, I don't know if it's worth adding it other than for the peace of mind.

 

i'm thinking I may go this route, anyone know why this steel braided hose wouldn't work? https://www.summitracing.com/parts/sum-230615

 

You'll have to convert to AN fittings vs barbed hose.
I was going to suggest that you could use hose that has a nylon shield. To get a decent clamp you would have to peel back the stainless hose to clamp the hose to ensure is doesn't leak. I would opt for fuel injector clamps over regular hose clamps.

 

how do you like the OBD app and the Veepeak scanner? keep it plugged in all the time?

 

thanks for the reply on the hose, I may just peelback the braiding to keep the barbs. Gathering all the parts and will do a transmission fluid change while I'm at it. I too have the vepeek OBD scanner and I keep mine plugged in all the time, it comes over on my car play so I can view all the time.

 

I like it. It's a useful setup (when coupled with the OBD Fusion App) and the price is nice. I usually leave it plugged in and will monitor data about every other drive. It's nice that it integrates with Apple CarPlay (mentioned above), but I usually have Maps up instead. I've got my phone mounted high using one of TackForm Vent Mounts. Since it's within eyesight, I usually monitor the data using my cell phone and I have custom dashboard setup in OBD Fusion so I can monitor a bunch of data in a single view.

That being said, I'm thinking of going the ScanGauge route eventually. Probably the SG2 mounted on the steering column like a lot of folks. Not in a huge hurry though.

On a side note: I did the drain & fill weekend before last. When I did, I decided to leave my catalytic converter shield off the truck for a while. I've noticed my temps have dropped a good 10-15 degrees at city & highway speeds. Upwards of 20 degrees cooler when I'm crawling up the mountain in 4WD. It was definitely sealing in the heat with the 4 cats on either side of the trans and really roasting it. Deciding between leaving it off permanently or taking a plasma cutter and cutting in a bunch of new ventilation holes in it.

 

What Cat Shields do you have?

 

Skeerdy Cat Shield/Skid Plate.

 

Thank you for that in depth reply! I have a 2014 and am curious to see how the temps on the tranny get. I don't want too hot of a tranny and his/her fluid. IF yo have a plasma cutter and don't mind altering the shields that would be my first option. I don't have shields but strongly consider it since its still and issue in my part of Texas. Bastards

 

Honest question: If you are going to pin the thermostat, why install one? Why not just tie in before the tranny fluid heater puck?
Thanks
Gil

 

You can run it straight to a cooler no thermostat. No warming puck. Good for warmer climates. You can also install a 165 deg thermostat. https://www.jegs.com/i/Improved-Racing/553/FSM-165/10002/-1

 

Thanks!

 

Hold up… what is this? Lol

 

And No puck - so warming up will be somewhat Slow....More wear in the meantime?

 

https://www.tundras.com/threads/wha...2nd-gen-tundra-today.68/page-525#post-3599719

 

https://www.tundras.com/threads/general-supercharger-thread.85513/page-670#post-3789836
Post 20089 above mine, the videos are good.

 

Great info and I see hotter climate LCs do not use one - thanks. This would simplify adding a trans cooler significantly.

 

Sooo...basically you screw in the 90° elbows and run lines to a transmission cooler? If it's that simple, I'm doing this ASAP.

 

You need 2 o-rings 90301-11030 that go with the elbows. You can throw on an inline thermostat later on if it's too cool. Innovate racing, derale, earls and mishimoto have decent thermostats.
Or like @snivilous did his cooler. Sorry for the hijack...

 

Awesome, thank you ever so much!

 

Drains battery. Not a problem in a daily driver, but something to keep in mind if truck is parked for weeks.

 

As far as thermostats - some coolers like the Hayden 699 model have built-in thermostats.

The odb2 veepaks have an On-Off button for long term storage Or you can simply Pull It Out. Makes the $5 app a blast to use.

 

I ran the hard lines and bolted them up in about 5 minutes. The most difficult part from what I remember was making sure I didn't touch the catalytic converter as they get hot even from just moving the truck into the garage.

 

I’m gonna do mine once @Jmunk gets those brackets for the Hayden made!!!

 

My 2020 was no fun either. Once I finally got the lines in place the back bolt was easy but that front mounting bolt was just buried. Many cuss words were uttered, but if I had to do it all over again I would still use the hard lines.