Transmission, brakes too hot?

[PatSoozy]

Good morning,
Questions first (BLUF)-The transmission gauge on our truck reports as a graph, not with numbers. Many have said they watch the transmission temperature to not exceed “x” degrees. Any thoughts on how far past 50% on the gauge is danger zone and I should pull over and let it cool down?
Second question, using an IR thermometer to check brake temperature on a down hill run, some have reported 200 degrees as “not to worry.” Any opinions on what is the “to worry” temperature?
Background, We are long time flatlanders heading for Utah via Colorado with a 2020 F150 SCREW 3.5 SB Max Tow, pulling a 2021 25GT FBT and not a lot of water, maybe 6600#.
Thanks in advance.

[GCinSC2]

PatSoozy,

Dexter info on drum brake temps. Remember its a brakes job to change kinetic energy into thermal energy via friction. No heat on brakes then they are not doing their job, of course how hot is based on braking load.

Sorry, can't assist with the TV trans temp query.

Gary

[PatSoozy]

Gary,
Thanks, that give me a range to look at. My understanding is that the transmission is to do most of the work on the down hill and use brakes sparingly (as needed of course!)

[jcl]

Originally Posted by PatSoozy

Gary,
Thanks, that give me a range to look at. My understanding is that the transmission is to do most of the work on the down hill and use brakes sparingly (as needed of course!)

I would say you are using the engine, more than the transmission. Transmission will heat up most when the torque converter is slipping, eg not locked up, on a climb.

I use the brakes more than sparingly, but I do not use them continuously. I brake the combination to bring it back down to my target speed, then release them. They cool then. If I have to do this cycle too frequently then I am in too high a gear.

[PatSoozy]

Understood, sparingly could imply not enough or real hard braking to bring the speed down. Keep at my target speed both going up and coming down. Not riding the brakes. Thanks.

[Jeff7176]

You can get actual trans temp to show on the dash. There is a program called Forscan that will allow you to do that, among other things. You need a laptop and an ODB reader.

[PatSoozy]

Forscan will do that? We almost needed Forscan when we were shopping for LED headlights. Definitely will investigate. Thanks!

[jcl]

Originally Posted by PatSoozy

Forscan will do that? We almost needed Forscan when we were shopping for LED headlights. Definitely will investigate. Thanks!

One thing to keep in mind if you get trans temp readouts is that modern transmissions such as yours are designed to run much hotter than transmissions from decades ago. Some have worried themselves when the transmissions were operating well within design specs, just because they weren’t used to seeing those temperatures.

[PatSoozy]

Gotcha. Given that I am totally unfamiliar with what are normal numbers, I think it will be much easier to follow data points as numbers (Forscan hack) than trying to watch the graph move. From there I can kind of establish a baseline of what is normal and what is out of normal.

[A B4 D]

I have the exact same setup but with a 2016 TV. I don’t get enough engine breaking even in third gear so brakes take more of the load than I’d like. The good news you won’t get more than 10 miles of continuous 6 degree downhill and I’ve never had an issue. (I live at 9000 ft and do alot of mountain pulling).Maybe the newer transmissions are better.

[GetawA-S]

PatSoozy,
I have a 2019 F150 XLT with the V8, no upgrade to the instrument panel. Using the selector on the steering wheel, I can choose “ display mode” on the driver display and scroll down to “transmission temperature”. My 10spd warms up to 195-200 F (best fuel economy) and will increase to as high as 215 on a steep climb. It seems to cool off as it “spins” on the downhill. Depending on how much your nerves can take, you can gear down and let the engine sing, using the brakes less than 20% of the time. Other than the programming quirks, these transmissions are very capable.

[jcanavera]

Keep in mind that some transmissions have a cooler that is immersed in the in the radiator. Thus in a climb as the water temperatures in the radiator increase, that temperature becomes the temperature of the fluid. Going back to my days of towing my first hard sided trailer with my '73 Oldsmobile Cutlass, I always used an external transmission cooler. Typically you mounted that cooler to the front of the radiator with long tie straps. You took the output of the internal transmission cooler (after the initial pass through the radiator) and rather return it to the transmission, you sent the fluid through the external transmission cooler and then back to the transmission. I was told that it would knock about 40 degrees or so off transmission fluidl, dependent upon the size of the external transmission cooler. I used Hayden coolers and it wasn't till I bought my GM vans that I found the towing packages usually included a separately mounted transmission cooler that was mounted in front of the radiator.

[JCWDCW]

You use the brakes to bring speed down 5 to 7 mph. Hard application is no more wearing than a hard application coming off the thruway
As jcl says… bring the rig back to your target speed… whatever you are comfortable with
If you are hitting the brakes too often especially on a long grade, you need to gear down.
On. 5 mile long 6% grade I would be applying brakes to reduce speed maybe 5 or 6 times pulling a ‘96 Excella wth my Dakota with OD off. Can’t remember the last time I needed second gear ( 2003 3-speed tranny)
JCW

[Wanderings]

Having driven big rigs, the rule of thumb is to use the same gear downhill as you would use going uphill. Of course, that’s just a rule of thumb.

[switz]

I have temperature probes in both the front and rear differentials and the transmission that display on my Insight gage system. I put oversized covers on both differentials that hold about a quart more fluid for additional cooling.

On a long steep climb, one will surprised to see how hot the rear differential fluid gets. So on my 2012 RAM 2500HD Cummins, I am watching the engine water temperature, engine oil temperature, EGT of the turbo charger, transmission oil temperature and the rear differential oil temperature.

What works the quickest is too slow down the speed and the temps will start to drop.

Engine braking with the diesel and lower gears allows me to make descents without touching the truck brakes with the 9,200 pound 31' Classic connected. I sometimes apply the trailer's 12" dual puck disc brakes by the hand control.

The gasoline Land Cruiser lacks the diesel's compression so I must be sure to be slowed down before the descent and select a lower gear. The hand control for the 23D's 12" dual puck disc brakes can keep the speed within limits.

The big secret when descending is to start down at a very slow (like 2nd gear speed) and see on the 9% (in some places out West) slope if that is slow enough to keep things under control. Also note the friendly sign that says emergency pull off in XX miles.

Applying only the trailer brakes will keep the rig in proper alignment.

[pjshier]

I went to the trouble to "activate" numerical temperatures above the graphs using Forscan but recently learned from another Ford truck owner that the numerical temps will appear above the graph once the temps reach above optimal range, anyway. I haven't seen this but several on the Ford truck forum confirmed it.

[pteck]

Downhill, it's practically impossible to overheat the engine or transmission. Brakes are a different story and it can be very easy to overheat the brakes on a long descent, if not used in conjunction with engine braking.

One way to look at this, for downhill braking
- Engine braking has infinite heat dissipation
- Caliper brakes have finite heat dissipation

In a long downhill situation, you'll want to use engine braking like it's going out of style. Use physical brakes judiciously. It's very possible to overheat the tow vehicle or trailer brakes (depending on bias).

It's next to impossible to overheat the engine and supporting transmission.

Don't be afraid to downshift to lower gear. More engine RPM will create more engine braking. Limit would be the engine red-line and modern ECUs won't let you overspeed an engine anyhow.

That said, the transmission torque converter will unlock and heat up to a degree on downhill. This is normal behavior.

I have an OBD-II monitor and have watched temps. GCWR of rig is ~15k lbs. At least on my Lexus LX570 (Lexus Land Cruiser, or very similar driveline to a Toyota Tundra), with a large factory transmission cooler, transmission temps are usually around 195-215*F under level cruise. There's two transmission temps, one at the torque converter, and one at the sump. Torque converter temp is much more dynamic. On descent with strong engine braking, 230*F would not be out of the question. These temps are mild for modern day fluids. On the most serious of climbs in Sierras and Rockies, putting close to 400hp down on very hot days, spinning say 3rd gear, 265*F is not underheard of.

[NevadaGeo]

Get used to using a lower gear on the up up upppity up and the down down downedity downs. The flat land doesn't have too many miles of those. Don't always try to pass everyone, even if your machine says it can.

[PatSoozy]

Wow, so many great points, my DW will be reminding me of them as we hit the road. We are three days out so I will now have to be responsible for implementing.
Good luck to all and safe travels.

[JA15830]

Originally Posted by pteck

Downhill, it's practically impossible to overheat the engine or transmission. Brakes are a different story and it can be very easy to overheat the brakes on a long descent, if not used in conjunction with engine braking.

One way to look at this, for downhill braking
- Engine braking has infinite heat dissipation
- Caliper brakes have finite heat dissipation

In a long downhill situation, you'll want to use engine braking like it's going out of style. Use physical brakes judiciously. It's very possible to overheat the tow vehicle or trailer brakes (depending on bias).

It's next to impossible to overheat the engine and supporting transmission.

Don't be afraid to downshift to lower gear. More engine RPM will create more engine braking. Limit would be the engine red-line and modern ECUs won't let you overspeed an engine anyhow.

That said, the transmission torque converter will unlock and heat up to a degree on downhill. This is normal behavior.

I have an OBD-II monitor and have watched temps. GCWR of rig is ~15k lbs. At least on my Lexus LX570 (Lexus Land Cruiser, or very similar driveline to a Toyota Tundra), with a large factory transmission cooler, transmission temps are usually around 195-215*F under level cruise. There's two transmission temps, one at the torque converter, and one at the sump. Torque converter temp is much more dynamic. On descent with strong engine braking, 230*F would not be out of the question. These temps are mild for modern day fluids. On the most serious of climbs in Sierras and Rockies, putting close to 400hp down on very hot days, spinning say 3rd gear, 265*F is not underheard of.

PTeck's advice is very good.

Another very good rule of thumb I learned on this forum is slow down before you get to the top of the pass.

I rely heavily on the Tow/Haul Mode. Didn't understand it until after I smoked a set of breaks on our F150. That cost me $1,200.

My mechanic told me that 4500 RPM is ok, but I don't keep that up for too long.