I was driving my 2500HD back to the farm after some grass mowing this afternoon. I'm moving along around 45 mph with about 500 lbs of mowers in the bed. All of a sudden the trans too hot light comes on. I look at the gauge and it's about 250F. After about 1 min the Idle Engine message appears. Fortunately I was only a mile from the farm. I pull into the shop, put it in park and pop the hood, engine still running, trans temp about 260F now. I start looking around, trans is full according to the dip stick, fluid looks good, no leaks visible, every things seems to be in place. I reach thought the grill and touch the tranny cooler, to my surprise it's cool to the touch. This seems very odd considering the tranny pan is to hot to touch.

So my question is, what the heck is going on??

Thanks,
Stephen

First off, was the tranny fluid too full at all? Where did it read on the stick? If it is not overfull, the I would have to say you may have a plugged tranny cooler- if it was cool to the touch I would think that would mean no circulation through it.

Tranny fluid was at the proper level and very hot. I've never heard of a tranny cooler plugging. Do they have thermostats that can fail??

Thanks,
Stephen

Another question, could the spin on filter be clogged??

Thanks,
Stephen

Another question, could the spin on filter be clogged??

Thanks,
Stephen

I doubt it as that would restrict the trim solenoids also and you would have shifting issues.

Mike, what should I check first? Have you seen tranny coolers plug up?? Is there a thermostat somewhere in the system??

This might be the perfect excuse to upgrade the cooler.

Thanks,
Stephen

Oh yeah, factory tire size, factory tune.

How long were you traveling at 45 mph? Were you using the T/H button? I have learned getting behind traffic traveling at those speeds will heat up the tranny in a hurry if you don't lock the TC. I have zero problems with my tranny normally running in the 175*-180* range when it's 100* outside but I noticed that I can quickly get up to 200+* under the above mentioned conditions unless I bump the button.
Reduced airflow and slipping TC = hot!

You are running a tune. Here's an earlier post by Crafty:
"Check the cooler inlet where the tranny line goes into the rad tank. Pull the line out and inspect for cardboard looking chips of paper. Clean it out if you find blockage. This would be paper coming off of the TCC LU clutch in the torque converter."

True, had been running a tune in the past. I'll pull the line and check.

I would start at the bottom cooler line ( TO COOLER ) at the trans and see if it's hot. If it is, then we know that fluid is flowing toward radiator heat exchanger. If as you stated that the cooler is cold, I would suspect the heat exchanger in the radiator is plugged with clutch material from a bad converter clutch. The trans cooler itself is not known for plugging as the radiator will plug first. An upgraded cooler will not solve your problem because we can only give you a 20-25 deg drop in temps.
I would get this taken care of asap because the return fluid from the cooler is the lube for your geartrain and it is now restricted with no flow from the cooler.

I'm going to tear into it on Sunday. Truck is not in daily service so it's parked for now. If the converter clutch has started to go bad, how much time do I have before it completely fails??

Thanks,
Stephen

Im no expert but i'd say if you have clutch material clogging the heat exchanger then you there now....i wouldn't want to keep running mine like that.

It will overheat if the cooler is clogged, but won't starve it for lube. The converter relief valve will open between 90 and 130 psi (depending on pressure in the lube circuit) to bypass around the cooler and dump into the lube circuit. The stacked lube and conv. relief valve setup balances dP across the cooler to maintain flow.

FYI. Some very early versions of the 1000/2000 BEFORE the Allison was used in the pickup did dump the converter overage back to pump suction inlet which would not allow lube if the cooler was blocked. In fact, you can still see the vestigial suction track going up there in the conv. housing but the wall in the front support was taken out along side into the lube track and the hole in the separator plate blocked.

It will overheat if the cooler is clogged, but won't starve it for lube. The converter relief valve will open between 90 and 130 psi (depending on pressure in the lube circuit) to bypass around the cooler and dump into the lube circuit. The stacked lube and conv. relief valve setup balances dP across the cooler to maintain flow.

FYI. Some very early versions of the 1000/2000 BEFORE the Allison was used in the pickup did dump the converter overage back to pump suction inlet which would not allow lube if the cooler was blocked. In fact, you can still see the vestigial suction track going up there in the conv. housing but the wall in the front support was taken out along side into the lube track and the hole in the separator plate blocked.

Thanks for the info.

Got into it this evening. It was clogged at the inlet of the side tank on the radiator. Thanks for the help guys.

Later,
Stephen

Greetings. What is the "normal temp" ? I have a 07 with 28K miles. It seems to run around the 150 mark with the outside temp at 70 - 80 degrees outside. This week had to run inland and pull 10 foot trail with furniture. Noticed the tranny temp was up to the 190 mark with ouside temp at 95. Coolant temp stayed around 190 - 200. Concerns?

Just fine. Depending on what you are doing, you may see temps over 200.

X2, that is quite normal and nothing to worry about.

Got into it this evening. It was clogged at the inlet of the side tank on the radiator. Thanks for the help guys.

Later,
Stephen

Plan on putting a new TC in it. The LU clutch paper will keep coming off and the problem will return.