AT Oil Temp at Highway Speed When Climbing Mystery (1 Viewer)

[NoTempoLimit]

I've owned my 2006 LC 100 with 125k miles for 2 1/2 months. I have the service history and baselined as much as I could. Not a peep (no CEL's no codes) out of that truck in the entire time (in stark contrast to most of the German cars I have owned in the past).

Now I'm on my first major road trip, and its an epic one: Southern CA to Southern Maine. I thought I had little to worry about since in driving the LC 100 for about 10 weeks there had been no signs of trouble.

I'm carrying a relatively heavy load, including a car top carrier and a cargo carrier on the tailgate. Yesterday, on I-15 in the CA desert (ambient about 105ºF) going up the very long Baker Grade, I am running cruise control at about 70 mph, with the trans selector in (D). I could tell when the torque converter lockup would disconnect, then if that wasn't enough it would drop into 4th.

The trans ended up holding 4th gear for a good long while on the Baker climb. When I would try to adjust the C.C. speed up a bit it would sometimes drop into 3rd. I didn't think much of it since the trucks computers (C.C., ECU and transmission computer) were controlling things and I never saw the coolant temp never went above 93ºC / 199.5ºF (50/50 Toyota coolant and water with 1 bottle Red Line Water Wetter).

After the Baker Grade this is one more climb before the Nevada border. I go up it the same way as before. Then on the way down I can tell something is wrong. The engine seems WAY down on power, and I can't increase speed even though I'm going downhill.

Then I get the AT Oil Temp light and somehow the engine stalls. This is at about 70 mph on an interstate. Once I get a sense of what's going on, I switch into neutral and coast down to the next exit.

I pull over and pop the hood to help the trans cool down. I don't see any obvious signs of trouble. I check codes with my scanner and the only thing I get is "System too lean bank 1/2". I clear the codes and having allowed some time for the trans to cool, I restart the engine and continue.

SO:

I need to continue the trip
I have the very steep 11,000ft+ continental divide to conquer tomorrow which makes Baker Grade seem like a mole hill.

Anyone have any advice?
Anyone experience anything like this?
Do I need to have anything checked?
Is it just a matter of climbing more slowly?
Is it best to not use cruise control and avoid 3rd gear on climbs?

Thanks in advance for your advice which is greatly appreciated!

 

[NoTempoLimit]

Forgot to mention: I got a ScanGauge II but I have not been able to get it to show AT Trans Temp. If that had been working I could have potentially avoided this problem since I was keeping an eye on engine coolant temps. If anyone knows how to get the ScanGauge to work with the 5 speed 2006/2007 LC please let me know. I've tried all the X-codes offered here so far and none have worked.

 

[gatormark91]

Check your AT fluid level. If you have an OBD-II dongle, the Torque phone app has a custom gauge you can set up that will show trans temp. I use it when towing. With heavy loads and steep grades, using OD can cause the trans to run way hotter than without OD, especially if there is an issue like a slipping TC lockup clutch or low fluid.

And totally unrelated.... Redline Water Wetter is just for use with straight water in race cars. It's useless in street cars because the temp is thermostatically controlled.

 

[Bomar]

You have to program the ScanGaugeII for trans temp... Search here and you will find the codes.

Also go into 4th gear and it will make the truck happier.

 

[bctlex]

I am in the middle of long road trip, from KY to Vegas, with lots of stops in Colorado. Different year and tranny LC here (mine is MY 1998). I have scangauge installed. I think the highest AT temp I have seen in ~180F (engine temp ~204F) while climbing steep mountains in Colorado. I do turned off OD. Truck is pretty loaded as well but without car top or cargo carrier.

 

[jLB]

ScanGauge Transmission Fluid Temp Codes for 2006 LC?

I've tried all the codes mentioned on this site and all the codes provided by ScanGuage and still can't get trans fluid temp on my '06 LC. Anybody got a set of X codes that work?

forum.ih8mud.com

A750F Transmission & ScanGauge II - What are your temperature readings?

In the constant quest for data, I realize that there is not a catch all thread for 100's with A750F's as there is for 100"s with the A343F (A343F Trans & ScanGauge II what are your temp readings?). Thanks for getting the ball rolling with the A343F @flintknapper! I installed a ScanGauge II on...

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[J1000]

Check your AT fluid level. If you have an OBD-II dongle, the Torque phone app has a custom gauge you can set up that will show trans temp. I use it when towing. With heavy loads and steep grades, using OD can cause the trans to run way hotter than without OD, especially if there is an issue like a slipping TC lockup clutch or low fluid.

And totally unrelated.... Redline Water Wetter is just for use with straight water in race cars. It's useless in street cars because the temp is thermostatically controlled.

How do you add the custom gauge in Torque? The same as for ScanGaugeII like Bomar said? Was looking for it the other day and didn't see it listed on the app.

 

[jLB]

How do you add the custom gauge in Torque? The same as for ScanGaugeII like Bomar said? Was looking for it the other day and didn't see it listed on the app.

Search for “xcode” or “x-code” on this forum. If I remember properly, there are some differences in the configuration based on year and transmission.

 

[NoTempoLimit]

Check your AT fluid level... With heavy loads and steep grades, using OD can cause the trans to run way hotter than without OD, especially if there is an issue like a slipping TC lockup clutch or low fluid.

And totally unrelated.... Redline Water Wetter is just for use with straight water in race cars. It's useless in street cars because the temp is thermostatically controlled.

I had the transmission fluid changed 2 months and 2k miles ago. The shop that did the work specializes in transmisions so its unlikely (not impossible) that that the fluid is low. I'll put that on the checklist.

So I take it that it is better to just sit in 4th gear for climbs? Thats' what the manual recommends for climbing and hard towing.

R.L. Water Wetter improves the heat extraction of the coolant. The idea is to provide an extra margin of safety. It is not going to make the engine run cooler than the ECU wants. But when the thermostat is wide open and the coolant can't extract all the heat, the coolant temp will be higher than what the ECU calls for.

I experienced this with an N54 (3.0L I-6 twin turbo) powered BMW. The coolant pump is electric and failed under warranty. I was running an autocross after that and my coolant temp were to high. It turned out the BMW techs put in 60% coolant! Diluted the coolant to 40%, added Water Wetter and that solved it. This is in SoCal where it never gets below freezing (although 33% coolant protects down to 0º F)

 

[abuck99]

Climbing steep long grades in summer heat with a loaded vehicle will put a lot of demand on cooling system and trans temps.

Try and keep your rpm’s up above 3,000 to circulate the coolant faster and also keep your truck in the higher in the torque curve. That might take you down into 3rd or even 2nd gear depending on the grade.

There is a small trans heat exchanger inside the lower tank of the radiator. As the coolant hits peak temps it will pull up the trans temps a little- so ensuring you have a healthy cooling system makes a difference: clean rad fins, fresh coolant at the correct level, clean atf etc.

Here’s the X code for trans temp for 04 and later

Scan Gauge X-Code for TFT
TXD: 686AF121B4
RXF: 046105B40000
RXD: 2808
MTH: 00090005FFD8

 

[flintknapper]

Climbing steep long grades in summer heat with a loaded vehicle will put a lot of demand on cooling system and trans temps.

Try and keep your rpm’s up above 3,000 to circulate the coolant faster and also keep your truck in the higher in the torque curve. That might take you down into 3rd or even 2nd gear depending on the grade.

There is a small trans heat exchanger inside the lower tank of the radiator. As the coolant hits peak temps it will pull up the trans temps a little- so ensuring you have a healthy cooling system makes a difference: clean rad fins, fresh coolant at the correct level, clean atf etc.

Here’s the X code for trans temp for 04 and later

Scan Gauge X-Code for TFT
TXD: 686AF121B4
RXF: 046105B40000
RXD: 2808
MTH: 00090005FFD8

^^^^^^^^^

Agree with this.

'Cruise Control' is fine for long flat stretches, but for other conditions (especially when the vehicle is loaded or you experience inclines) driver input is best way to go. You have gears for a reason...use them as necessary.

 

[ga12r1]

^^^^ What Buck said. Try running OD off at around 3200 rpm. That should keep you at around 170ish on trans temp even under a very heavy load and high ambient temps. Coolant temp may get up over 200 but as long as it holds and cools down after the grade you’ll be ok.

 

[gatormark91]

Your fuel pump might also be getting weak (the "Too Lean" code). If the trans is getting hot, and you have a cargo carrier on the back, the heat buildup in the fuel system from the long climb could be more than a weak fuel pump can overcome. That could explain the lack of power and eventual stall out. When it all cooled off, it ran OK again?

 

[NoTempoLimit]

Climbing steep long grades in summer heat with a loaded vehicle will put a lot of demand on cooling system and trans temps.

Try and keep your rpm’s up above 3,000 to circulate the coolant faster and also keep your truck in the higher in the torque curve. That might take you down into 3rd or even 2nd gear depending on the grade.

There is a small trans heat exchanger inside the lower tank of the radiator. As the coolant hits peak temps it will pull up the trans temps a little- so ensuring you have a healthy cooling system makes a difference: clean rad fins, fresh coolant at the correct level, clean atf etc.

Here’s the X code for trans temp for 04 and later

Scan Gauge X-Code for TFT
TXD: 686AF121B4
RXF: 046105B40000
RXD: 2808
MTH: 00090005FFD8

 

[NoTempoLimit]

Yesterday it was raining the whole way (in the desert!). Temps stayed under control. I did notice that the engine ran slightly cooler (89-90ºC) without the AC on.

Did not use cruise and climbed in 4th. Dropped into 3rd briefly on some really steep high altitude climbs.

It seems the lean codes had something to do with the heat. That problems has not returned.
Keep getting an emissions related code P0420 but no problems other than that. ScanGuage comes in handy to quickly clear the code.

For some reason VSC OFF TRAC OFF lights come on when the MIL (check engine) light comes on. What do the two things have to do with each other?

Cannot get ScanGuage to display Trans Fluid Temp. I just get a blank in that spot after entering the X-Code. What could be causing that?

 

[geanes]

OD off/3200 RPM is the key. Just towed a small trailer behind my 98 LX all over Colorado (Raton Pass, Marshall Pass, Los Pinos Pass, Cinnamon Pass, California, Hurricane, Coal Bank and Molas Passes). On the flatter TX highways, I could run with OD on with no issue and trans temps rarely climbed above 170. Once I hit NM and the elevation began a steady climb from 3k to 6k, I turned OD off and cruised the rest of the way all over CO that way. Never saw temps climb above 170. Molas and Coal Bank are long, steep, slow climbs out of Silverton heading to Durango. Our rigs just seem to really prefer higher RPMs when towing.

 

[blatant]

Isn't the truck designed for heavier duty use? Africa/Australia/Middle East [hotter than here] You guys have me thinking to add one more thing to obsess about! Now I need to get a gauge and study the engine temps. Can the gauge read brake temps too, may as well add that. I live in the hottest place in the USA, big hills too and the truck runs great, towing or not. With A/c, cold as can be, even in stop and go. Maybe the AUX fan has something to do with it or maybe all in my head!

 

[NoTempoLimit]

OD off/3200 RPM is the key.

I wish they would explain this stuff in the owners manual instead of dumbing everything down.
Going to stop by Slee in Boulder today. Should be able to get some good advice there.

 

[blatant]

@NoTempoLimit circle up with @LandCruiserPhil he makes and additional fan kit that gets rave reviews. Plug and play.

 

[NoTempoLimit]

Isn't the truck designed for heavy duty use? Africa/Australia/Middle East [hotter than here]

True but those Cruisers have a different spec. Might have different cooling systems and less safety/comfort gear for less weight.
I am starting to wonder if I really did get the transmission too hot. Hopefully I can find someone that can connect to it and pull the log.
Would the transmission temp cause the ENGINE to go into limp mode? Even if so it seems odd that there would be no warning. It would have been better if the A/T OIL TEMP would light up yellow first. Thats why I HATE idiot lights. If I'd had a gage I would have noticed the temperature trend and moved over to the right lane to slow down and stop if needed.