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Old 06-27-2012, 10:51 PM   #29
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Noob here and learning by reading.

I have some questions. How are you all monitoring your temps so precisely? Do your tow vehicles come with built in monitors?

What is transmission lockup?
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Old 06-27-2012, 11:15 PM   #30
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Noob here and learning by reading.

I have some questions. How are you all monitoring your temps so precisely? Do your tow vehicles come with built in monitors?

What is transmission lockup?
I use a "Scangauge II" device that plugs into the OBD-II port. On my '07 F150, the transmission temperature is available from the OBD-II bus, but I had to do a little programming on the scangauge because it isn't one of the standard registers, it varies from manufacturer to manufacturer. The information for doing so was readily available on the internet (imagine that!)

To explain "lockup" I need to know you understand the basics of how the torque converter works. A conventional automatic has a viscous fluid connection between the engine and transmission called a torque converter. The engine imparts rotational force into the transmission fluid, and the fluid transfers SOME of that force to the transmission. The benefit is that the engine can run while the transmission is in gear as long as the engine is turning below the converter's "stall" speed, and the engine can turn faster than the transmission to allow the engine to be in its power band more of the time, etc. The downside is that they're less efficient than a conventional clutch, some power is lost in the process.

In the '80s car manufacturers started using torque converters that could "lock" the interface between the engine and transmission so that the input shaft to the transmission has a direct mechanical connection to the engine. As far as I know, all modern torque-converter automatics have a lockup torque converter.
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Old 06-28-2012, 05:26 AM   #31
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Quote:
Originally Posted by bonginator View Post
Noob here and learning by reading.

I have some questions. How are you all monitoring your temps so precisely? Do your tow vehicles come with built in monitors?

What is transmission lockup?
If you don't have a tranny temp gauge, it's not a difficult up-grade.


Lockup is lockup, direct connection thru the transmission, the torque converter is no longer converting torque.

Bob
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Old 06-28-2012, 06:27 AM   #32
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I had a gauge installed in the B190 when I put the new transmission in. I rarely saw it get above 180 degrees even on hot days while towing a car over the Appalachian Mountains. It was great. I decided I would start freaking out at 220, but I never saw it get anywhere near that high. (NOTE: You'll get different readings depending where you measure it! Mine was measured in the pan. So 180 might be equivalent to 220 in another part of the system.)

When we were looking at the F-250, I was happy to see that it has a transmission temperature gauge built in, though it's not marked numerically. I can live with that: If it's going off the top, I know it's too hot. And it doesn't really matter what temperature that's happening at, does it? It's too hot and that's all that really matters.

Keep in mind the transmission is building up heat while you're driving, but it also has a cooler just like the radiator. If you're moving, the airflow is going to help keep the fluid cool. If you're sitting in traffic, though, that airflow isn't as good.

Does anyone know if the engine computers smart enough to turn on the fan for the transmission temperature? Or are they still only activated for coolant temperature?
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Old 06-28-2012, 07:07 AM   #33
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Not sure on the M-B...

On our Burb the PCM will activate the electric cooling fans according to engine temp and AC mode.
Sustained transmission temps above 280* initiate a "limp" or cool down mode, and at those temps I'm pretty sure the Aux fans would be running.

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Old 06-28-2012, 08:11 AM   #34
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I traded an '06 GMC 2500HD in on a '12 Chevy 2500HD. My transmission cooler problems are listed on another thread. However, the GMC has a temp gauge on the dash....in order to check the trans temp on the Chevy, you have to go through a menu for a digital readout!
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Old 06-28-2012, 08:48 AM   #35
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I had a gauge installed in the B190 when I put the new transmission in. I rarely saw it get above 180 degrees even on hot days while towing a car over the Appalachian Mountains. It was great. I decided I would start freaking out at 220, but I never saw it get anywhere near that high. (NOTE: You'll get different readings depending where you measure it! Mine was measured in the pan. So 180 might be equivalent to 220 in another part of the system.)

When we were looking at the F-250, I was happy to see that it has a transmission temperature gauge built in, though it's not marked numerically. I can live with that: If it's going off the top, I know it's too hot. And it doesn't really matter what temperature that's happening at, does it? It's too hot and that's all that really matters.
t

Ah - my Tundra has a gauge that looks like the Tekonsha but dosnt have the numbers so I can at least watch it. We towed last week over several CO passes and sometimes it would go a bit above. Midway on long slow 8 pct grades but then back to midway after that. Now I understand ether what that gauge is telling me.
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Old 06-28-2012, 10:07 AM   #36
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"A fact to consider with aftermarket coolers is that over a number of years the lines can become a fruitful source of leaks which, if not identified and corrected in a timely fashion, can cause more damage than hot fluid."

But remember the OEM trans,power steering,fuel and brake lines are never a source of leaks.

Inspect on a regular basis.
True that, although, in my experience, the aftermarket coolers don't use hoses and connectors that are as well designed as OEM. I just replaced some that apparently were installed new by the dealer on a Dodge Intrepid. The thing has never had a trailer hitch so I don't know quite what they were thinking.

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Time under load with the torque converter unlocked generates the most heat. Pulling away from stop lights is a condition where you have torque converter unlock until the upper 3rd gear area. A long grade in 3rd gear most often has the torque converter engaged, until a 2nd gear downshift.
There is also quite a lot of heat dumped into the fluid from upshifts under power including the locking of the torque converter clutch. Pulling away from a red light on a highway I'm applying full power through the 1-2 shift and close to it for the 2-3 shift.

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Noob here and learning by reading.

I have some questions. How are you all monitoring your temps so precisely? Do your tow vehicles come with built in monitors?
Some trucks come with built in gauges. My 2006 Chevrolet does, as does a friend's Nissan Titan. Otherwise they can be added.

In practice the information they supply isn't that useful on a modern transmission. Most trucks with gauges already have auxiliary coolers, so it doesn't help with that decision. Maybe in some cases it can influence your driving style but I think that's rare. Maybe in some cases it can provide some advance warning of impeding transmission failure, if there are clutches slipping or something else causing overheating.

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Does anyone know if the engine computers smart enough to turn on the fan for the transmission temperature? Or are they still only activated for coolant temperature?
I believe that on my Suburban the computer moves the shift points around (mostly by delaying the 3-4 shift and locking up the torque converter in 3 and leaving it that way) and engages the clutches faster (firmer shift) as the temperature goes up. At least it seems to. On electronically controlled transmissions, which is most everything after about 1990, the clutches are engaged through a modulator that allows the computer to vary the firmness of the shifts.
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Old 06-28-2012, 01:11 PM   #37
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Back in the day, I had an Astro van when I got my 22' SOB. While I was barely within tow limits, it was underpowered. Back then you could jump the A pin to the H pin (IIRC) on the ALDL connector and lock the converter with a switch whenever you wanted to (above 30mph...again IIRC) This allowed me to run in second gear up long hills WITH TCC engaged. Can't do that anymore....plus the more modern trans' will do all kinds of overheat protective things that the old ones (early 90s) weren't capable of.
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