Heading up the canyon the other day and the trans temp light came on. Being a highway under construction I had no place I could pull over for over a mile but by then the light had gone out. Today, it about the same distance from the house the light came on again but I was able to get over and do as the manual says and put in neutral and run above idle...It took about 3 seconds of that for the light to go out. I continued up the canyon and the light did not come back on.
So, I decided to do a radiator flush as the 120,000 mile services are due thinking that that may help the transmission cooling.
As I was doing this I realized that there is no separate trans cooler, just a loop of tubing in front of the radiator. Is this all we get as a trans cooler? The trucks build sheet says factory installed tow package, I would have thought for that there would be a separate radiator for trans cooling.
I am thinking about getting a trans flush but bought the vehicle at 105K and now with 124K if I should as I have heard horror stories about changing the fluid in older transmissions.
Oh, the trans lines, yep, leaking, sorry about the huge pic, copy/paste...could that be contributing to the light? I checked the trans fluid level, a touch below the hot, but not to the add line.


Looking on line I couldn't find any pics of the radiator front so here I am, once again, humbly asking those much more in the know what's up...
Thanks in advance for any insight.

Oh, yeah, I live in Salt Lake and it's been almost 100 degrees everyday for a month.

 

IIRC, the factory tow package was that the trans cooler was part of the radiator. Not really sure what's up with yours. I occasionally get the trans temp light for no more than 5 seconds, and im fairly sure it's because my torque converter is cooked.

 

Well that doesn't sound good. Just wondering what makes you think TC? Do you have other symptoms as well that make you lean that way?
Do you think a fluid flush is a good or bad idea at this point?

I have also not done a "hard" road test since the radiator flush yesterday. By hard I mean pulling Parley's canyon on I-80 out of SLC. It's a 3,000 foot elevation gain over 10 mile run topping out at 7,000 ft.

 

Went out for a hard test drive, stopped by the store for a qt of AT fluid just to top off. Didn't make it far from the store and the light came on, got pulled over right away, shifted to neutral, high idle, 15 seconds light out.
I turned around and stopped by a buddies house to BS and let everything cool down and have a escort/tow home if needed.
Gave it a couple of hours, well below normal operating range when I headed out. Made it about 2 blocks and light on...I was at a red light so I slipped it into neutral gave it a rev and light out. Truck was still not up to normal operating range.
That is throwing me. That the trans thinks it's hot but the engine is in the 160 range.
I drove it the 2 miles home, checked fluid, right where I filled it to. No smell. The new bottle smells more like ATF than the old, but no burned smell.
The radiator flush I think was a complete success, running well below the mid line with the A/C cranked so I don't think it's that.

I Figure I should take it in for a filter and complete fluid change tomorrow. I don't know if it's ever been done on this truck as I bought it with 105 and I'm at 127 now.

 

I have a bit of a shake below about 1500rpm. Talking to a transmission guy at work, he said that and random heat/pressure spikes are classic TC.

I have gone for drives with my live data scanner attached... temp will be solid at 180F, and suddenly jump to 280, and then suddenly back to 180F again. I'd pull over and hit my pan with a thermal gun - 180F. That sudden jump makes me think it's electrical. The other interesting part to me is that it only seems to happen once per drive cycle - no matter how long a drive I go on, it will come on once, and only once, until I turn the key off. Could also be something in the pump. That's known to happen.

I'm currently planning an engine & trans swap, so if it can make it a few more years, I'll be a happy camper.

 

I would replace the transmission cooling lines before the leaks get worse. Just did mine and installed new lines instead of splicing, PIA.

 

I think your problem is with the temp sensor in the tranny, I would bet if ypu put an infared thermometer all over your trans you will see that is operating normally. test some fluid off the dipstick if you are really concerned. willing to bet this is just a moot issue.

 

Flushed and filled the Trans with new blood. Did hard test, no problems so far. Not up the canyon, not in stop and go traffic

 

Replaced both trans filters along with transfusion of ATF4.
Hard test, up canyon in 100 degree heat, A/C on...no lights, no hesitation, smooth shifting, downshifting for the climb...seems OK but I drive this truck not so much, so it will have to do a couple more trips before I am confident.
Temp was just above the mid line and dropped right back to almost cold on the downhill side.
Thanks for the replies, I'll post again if the problem reoccurs.