Using a ScanGauge to monitor towing performance? - Page 3 - Escape Trailer Owners Community

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Old 09-19-2014, 07:31 PM   #21
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Great info, Dave.

Quote:
Originally Posted by ice-breaker View Post
I did notice really early that the transmission temperatures are about 10-20 hotter if I forgot to use 4th gear while towing and left the transmission in D. Apparently, this is because the torque converter is locked when driving in 4th.
I doubt that's the reason. The torque converter is not simply always locked in 5th gear or when D is selected (which are not quite the same thing), and it probably locks up in at least 4th and 3rd as well. I think a more likely explanation is that there may be less fluid flow in 5th gear than in lower gears, and the flow is needed for cooling.

GM transmissions - for example - lock the torque converter more in tow/haul mode, because locking that clutch reduces heat production by eliminating power loss in the torque converter.

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Originally Posted by ice-breaker View Post
Of the two temperature sensors on my transmission, one of them is much more sensitive to temp changes than the other, and tends to climb rapidly when the transmission is working hard. From posts by others on the FJ forum, it seems that this sensor may be located right at the outlet from the torque converter.
Yes, that makes sense to me. Even without the extra cooling capacity of a towing preparation package, there will almost certainly be a transmission fluid cooler (usually integrated into the radiator). The one which fluctuates more is likely near the outlet from the transmission to the cooler, and the other one may be close to the inlet from the cooler... but that's just a guess.
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Old 09-19-2014, 08:37 PM   #22
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I experimented with towing in D on the flats and did see the torque converter lose lock. That didn't happen in 4, so that's what I always used when towing.

It is true that when unlocked, a lower gear and higher rpm will result in lower transmission temperature for a given speed, but that is by far a smaller effect than lock/unlock.

Bill R
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Old 09-19-2014, 10:47 PM   #23
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I just tried out my ScanGaugeII today to test my newly added B&M external cooler I mounted forward of the AC condenser. All of this is pre-acceptance of my 21' next month. My vehicle is a 2003 V6 4Runner, and I was concerned when the transmission temp showed 200F driving up the 1500 ft. elevation grade of our home town Signal Mountain, which is 6% average with one stretch of 8%, but not towing anything in 85 degrees.
Since the transmission temp was often higher than the coolant temp, I have to assume the readout is leaving the pan, and not after being cooled. My external cooler is in series (after) the radiator. Maybe I also have two sensors like Ice-breaker's much newer Toyota. Anyway, this is to report that the X-gauge codes do exist for a 2003. I can forward, if someone needs the codes I have. I'll see if I can load the others for the cooled fluid tomorrow.
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Old 09-20-2014, 12:11 AM   #24
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Quote:
Originally Posted by Bill R View Post
I experimented with towing in D on the flats and did see the torque converter lose lock. That didn't happen in 4, so that's what I always used when towing.
That makes sense, if the transmission controller was looking for a bit lower gearing while in D position and 5th gear.

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Originally Posted by Bill R View Post
It is true that when unlocked, a lower gear and higher rpm will result in lower transmission temperature for a given speed, but that is by far a smaller effect than lock/unlock.
... meaning that the big effect is higher fluid temperature when unlocked, right?
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Old 09-20-2014, 08:03 AM   #25
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How does one know the torque converter is locked or not?
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Old 09-20-2014, 01:49 PM   #26
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Quote:
Originally Posted by padlin View Post
How does one know the torque converter is locked or not?
There's no really easy way to tell, such as an indication on the instrument panel.

The torque converter is like a reduction gear set: the output speed is less than the input speed, and when it is usefully doing its job, the output torque is higher than the input torque. It's even continuously variable: the ratio of input to output speed varies. When it is being useful, it is in "torque multiplication" mode. When it isn't trying to multiply torque, the output is nearly as fast as the input (with no more torque), and the speed difference between input and output (about 10%) is just slippage, leading to wasted power and thus heat production. This operation is called "coupling mode".

The lockup clutch locks the input of the torque converter to the output, so the torque converter then doesn't do anything, and doesn't waste any power, instead of running in coupling mode. That means you can tell when the clutch engages because there is a small change in engine speed (that 10%) with no change in the speed you are driving. This is usually different from the engine speed change resulting from an upshift (a change to the next higher gear), because the change due to lockup is smaller than the difference between gears.

There are three challenges in spotting this behaviour:
  1. If you just look at engine speed and road speed, you would need to do calculations based on the gear ratios or a list of engine speeds with corresponding road speeds to guess what gear you're in and whether or not the clutch is locked up.
  2. With so many gears (or "speeds") in modern transmissions - up to nine - the change between higher gears is not much different from the change due to clutch lockup.
  3. If the clutch engages when the torque converter is still in torque multiplication mode (which generally shouldn't happen), the engine speed change would be greater than normally expected.
Perhaps the gear and clutch lockup information is available on the vehicle's diagnostic network, so the right codes could allow a ScanGauge to read them?

Of course, the point of automatic transmissions is to not have to worry about monitoring engine speed and controlling the transmission...
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Old 09-20-2014, 04:12 PM   #27
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Quote:
Originally Posted by Brian B-P View Post
... meaning that the big effect is higher fluid temperature when unlocked, right?
Yes.

Locked temps were 140-160 degrees F. Unlocked temps were typically 170-190 degrees F. So about a 30 degree difference.

Unlocked in 4th was about 190 degrees F and unlocked in 3rd was about 180-185 degrees F. So it helps to use a lower gear and higher rpm, but only by 5-10 degreees.

So the lock matters much more than the gear, at least for our 4Runner.

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Old 09-20-2014, 04:28 PM   #28
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Quote:
Originally Posted by padlin View Post
How does one know the torque converter is locked or not?
Two ways:

1. If you have 2 transmission temps, one from the torque converter and one in the pan like ScanGauge provides for late-model Toyotas, and the temps are the same, then the torque converter is locked.

2. If you have a tachometer, you can see the lock with a little practice. Accelerate into the gear, then ease up to just maintain speed -- lock will happen within a few seconds and you can see the tachometer drop about 200 rpm. On our 4Runner, accelerate to 50mph in gear 4, ease up, and watch the tach drop a bit. Also, when you have lock and accelerate, you can see the rpm's go up before the road speed, which means the torque converter has unlocked. Accelerating too much and you'll downshift, and accelerating not enough will leave it locked.

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Old 09-20-2014, 05:35 PM   #29
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Well thanks guys, after seeing how cool the ScanGauge 2 is I had to go and order one! There goes $150
Of course we don't have any camping trips on the horizon right now, but it will be great for an upcoming drive down to CA without the trailer, just to get a baseline.
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Old 09-25-2014, 02:24 AM   #30
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Quote:
Originally Posted by fudge_brownie View Post
I wanted to install one but found out ahead of time that there are no codes or no sensors for transmission temperatures on my 2003 4Runner. There are a lot of nice features but one of the key to monitor is trany temp. It appears from the prior post that even later Toyota vehicles have issues with getting readings.

It sure looks like a nice tool and I know you will have some good benefits with it installed.
I found the transmission code for my 2007 Toyota Sienna and it works great. I did hear that older Toyotas are a problem.
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