I think I got lucky....hot transmission

Jms

My wife and I headed to Hualapai Mountain Park last weekend outside of Kingman, Arizona with out T@G Outback 6W. Long windy mountain road up to the campground. The person at the entrance charged me the camping fee and directed me to an upper loop in the campground. Well, about half way up the steep, one-way road my transmission temperature light came on (bad). I stopped immediately (good) and turned the car off (not the best choice - should have put it in park and idled it). Popped the hood to help cool (good), and scouted behind me for an escape. I ended up backing down about 300' of 8% grade one lane road (did I mention it was around a curve too, ugh!) to a point I could disconnect the trailer, turn the TV around, and reconnect. By the time I got to the bottom, the light had gone out (tranny cooled while I was backing). But I thought I could smell hot transmission fluid and feared the worst. We went back to the lower loop and found a good spot to stop for the night and worry. I checked the transmission fluid level after it had cooled some more, and the level was good. But I could smell a strong petroleum odor on the fluid. Crap. I ran the diagnostics on the bluetooth ODBII reader I had picked up a few weeks ago, and no error codes from the engine. That was good. It was time for a fitful sleep.

We returned home the next day (about 90 miles), and I made an appointment at the local Honda shop to have the transmission checked out. I think we got lucky. The mechanic said the fluid smelled "slightly burnt", but he didn't find any fibers in the fluid. Whew. He changed the fluid and suggested I come back in 1000 miles for a second fluid change. My wife has the vehicle in CA this week, and we'll change the fluid again when she gets back.

So I was kind of lulled into a little complacency by the fact that our TV (2015 Honda Pilot AWD) has a tow rating of 4500 lbs, a 3.5 liter V6 engine, and a transmission cooler standard. We didn't have much equipment since it was a quick trip (maybe 100 lbs), and the trailer didn't have any gear except the 11 gallons of water on board. And it was only 70 degrees outside. Why did the transmission heat up so much? Well, it must have been the slow speed due to the narrow roads (I was going 30 mph max on the way up for about 10 miles and then much slower in the campground) and the steep grades. Not enough air flow. As WilliamA said in another thread, the heat will kill a transmission. But still, I'm curious about folks towing with much smaller engines in mountainous areas. A number of folks in the forum have mentioned using smaller Subaru's with 2 liter engines to tow around Colorado and other places. Is there something else I'm missing in the equation of TV tow rating and engine size? And I would have thought the transmission cooler would have helped more. Thoughts?

I've had a bluetooth ODBII reader for a while now, but I'm having a devil of a time figuring out the Honda PID code for the transmission temperature sensor so that I can have a readout of the temperature on my phone using the ODBFusion app. I'm going to have another go at the Piloteers forum and try to figure the code out again. Even the Honda shop couldn't find the right code on their professional reader to share with me. @#$% Honda.

WilliamA

I'm not a Honda guy (motorcycles, yes. Cars, no.)

Miles on the car?

CVT?

Altitude?

Did you force a shift? By that I mean, did you manually shift to a lower gear? Forcing the shift will keep the transmission in a lower gear. Where the tranny will be much happier. It will also circulate transmission fluid faster as the pump is on the input shaft of the transmission. More engine rpm's=more pump Rpm's=faster circulation. On my Jeep when pulling my trailer, I force-shift it constantly. Any time I feel that the engine is "lugging" in too high a gear whether creeping down a logging trail or blasting up the highway at 65mph I'll slap it down a gear or 2. For going up a hill like you describe at mall-crawling speed, you should be in 1st or second. Your transmission will thank you. Your Honda owners manual should have the dirt on shifting. If it's a CVT,, well.....good luck. They don't like low speed, high torque driving. And yes! If the tyranny smells hot or you get a warning light, pull over, Put it in Park or Neutral and let it idle. That will circulate the fluid through the cooler and bring the temperature down. Generally speaking, auto trans temperatures will run hotter than engine coolant temps but the fluid will start to start to break down above around 240 degrees. If you have an external oil cooler that depends on airflow, it won't do fiddly at walking speed. Most transmission oil coolers work by running oil through the radiator where engine coolant is the heat transfer substance. At high altitude, all cooling is less effective. High engine temps like those experienced at high load, low speed will rapidly contribute to transmission overheating. Almost always, engine rpm's are your best defense. The engine spins higher but under much lower torque loading, hence, less heat and also much faster fluid flow, both engine and tranny.

Live long and prosper (at higher rpm's)

WilliamA

LuckyJ

All that @WilliamA said, plus, and about fast towing, this is one of the reason that Overdrive should not be used while towing.

Have fum outhere!

Jms

Thanks WillaimA and LuckyJ.

WilliamA will probably agree with one of my favorite YouTube mechanics...Honda makes great engines due to their experience with motorcycles, but their transmissions are weaker being designed and built by Honda.

The Pilot has only 35,000 miles on it, and the transmission fluid had not previously been changed. I purchased the vehicle from the dealer used with 15,000 miles on it - it had just come off of a two year lease.

Transmission is 5 speed automatic. No CVT.

Elevation was probably around 7000'.

I should have been in first gear going up the hill in the campground. I did not manually put the transmission in first, but I was starting from a complete stop and the automatic transmission did not up shift. I always use the gears going down hill, constantly down shifting to use the engine for slowing the vehicle. People behind me probably wonder why my brake lights don't go on. I don't usually manually down shift going up hill, but I will pay more attention in the future. I was definitely at crawling speed going up hill - maybe 5 mph or slightly faster.

The coolant temperature gauge never went above the normal point, so the transmission was definitely hotter than the coolant. The external transmission cooler is mounted in front of the radiator, and there are two large electric fans behind the radiator (kind of wonder their purpose if they aren't circulating the air at the crawling speed I was going). Makes sense what you are both saying about RPM and circulation. I will be more mindful of that in the future.

Would you be concerned about any longer term problems due to this experience? Since the mechanic didn't find fibers in the fluid should I assume all is well? Definitely don't want to be in the back country and something go out. AAA wouldn't appreciate that call. And I don't want a $2,500 tow bill.

And I always appreciate your words of wisdom and iconic references, WilliamA! :-)

WilliamA

I am going to go out on a limb here and say your transmission is going to be okay. As long as the fluid was changed and there wasn't any particulate in it you should be fine. Keep in mind that in the age of "smart" vehicles everything from gear strength to shift points is designed to squeeze mileage at the expense of all else. For example, your transmission may not stay in first or even start out in first depending on the program. Some transmissions also will be programmed to start out in second to reduce wheel spin under certain conditions. Automatics use pump pressure to keep the clutch packs engaged and when rpms are low, there's less pressure and hence, more clutch slip. The primary culprit of transmission trouble is clutch slipping. More rpms equal better clutch engagement. The oil cooler question is a debate that's raged for a long time. More isn't necessarily better as air cooled heat exchangers have small passages and a nasty habit of reducing flow as a result.

Auto makers hate trailers. They would outlaw them if they could get away with it. It changes EVERYTHING. It's up to the user to be wise and find the best way to do it.

WilliamA

Joabmc

You might consider going with an aftermarket transmission cooler that has a little more guts to it. Also might be a good idea to purchase the Torque Pro app and OBDII dongle. That will allow real-time monitoring of temps in the future. Glad you caught it right away... @ 35K, you should be fine.

Jms

Thanks WilliamA. I appreciate your optimistic arboreal gymnastics.

Good info to think about regarding the computer systems. I know our AWD will engage when stopped and stay engaged until the vehicle reaches speed, even on flat terrain. So I'm pretty sure I was in AWD going up the hill. Next time I will definitely downshift into 1st and make sure I have better RPMs to engage the clutch packs and circulate the fluid. I was probably "babying" it a bit too much up the hill keeping the RMPs low, which was probably causing some slippage in the transmission and resulting in additional heat. Alas, I miss manual transmissions. Good info to think about with the cooler also. I probably put too much faith in it as a "feature."

As the old saying goes, good judgment comes from experience. Experience comes from bad judgment. I just gained some experience and hopefully some good judgment for the future.

Jms

Thanks Joabmc. I'll have to compare the stock cooler with an aftermarket one. The cooler was replaced about a year and a half ago after an unfortunate meeting with another vehicle driven by little ole lady on the Navajo reservation. A long story for another time.

I don't have Torque Pro since I'm running all Apple products (not a fan boy; I just like things that work), and Torque Pro isn't offered as an iOS app. I'm using OBDFusion with a bluetooth OBDII reader. The system works well, but Honda is a pain when dealing with the proprietary PID codes. And the transmission temperature sensor is one of those codes. I've seen several posts on the Piloteers forum regarding codes that worked, but I can't seem to get it to work for me. Even the dealer couldn't access the sensor from their OBD reader. Stupid Honda. More research and fiddling to do.

Appreciate the support!