Transmission Temperature

[Traveler II]

We have a transmission gauge that tells the temperature, but I can’t find anyplace that tells me at what temperature I need to be concern with. We are traveling in AZ and today it was 97, not towing we were running 160 degrees. Outside temperature seem to have more to do with the gauge than pulling.

When should I be concerned?

[Rob & Cathy]

I think you'll find that in the area of around 210 is the cautionary zone. If you hit 220 you may overheat the ATF and change it's properties. The rule of thumb is if you go over 220 to change the ATF as soon as you get the chance.

Is your gauge build into the truck or is it aftermarket? The reason I ask is because the easiest place to attach the sensor is in the pressure port of the transmission. When connected to the pressure port you are actually reading the case temperature which will be about 10 degrees cooler than the ATF temperature.

Rob

[Mike Clay]

Your good at 160 but if you get to 220 for very long your toast

[Traveler II]

Thanks for the info.

The readout came built in from the Chevy.

[campswithcritters]

I have the Chevy with factory gauge also, yes the outside temp varies it a lot. When in the mountains it often hits 200, which is when I just reduce the power a bit, I have seen it at 210 on extremely long steep pulls, but then you will hear the fan clutch kick in and I've not seen it go higher. When you get the fluid changed see if you can find an allison authorized shop and get it changed to transynd fluid, I plan to do that and they say that fluid will go higher in temp without damage.

[lapriester]

Above all, in any tow vehicle, the first thing you need to do is change to synthetic fluid. CRITICAL. With synthetic, 220* or even 230* for short periods does not mean you need to rush down and change the fluid. Synthetic fluid properties do not change at that temp unless it's sustained for very long periods. Dino, fluid, on the other hand, is toast. The evidence is just looking at the fluid. Dino fluid will begin changing color to a dingy brown when overheated yet synthetic will remain bright and red.

Synthetic fluid retains it's shear strength, and viscosity whether it's very cold or very hot. With dino you'll find hard shifts in the morning and slip shifts as the fluid gets too hot primarily due to the viscocity changes that occur.

Another critical addition to any tow vehicle is the installation of the biggest stacked plate auxiliary cooler that money can buy. Not those finned aluminum Hayden VW style cheapy coolers. I'm talking one of those 40-50K Tekonisha or True Cool beasts. A good option for up to 2003 Ford trucks is to add the cooler from a later Super Duty 6.0 diesel truck. Any cooler you use should be installed in series with your original cooler for max cooling capacity.

Some say that running a tranny too cool is as bad as running it too hot. That is just not the case if you are running synthetic fluid since the issue is high viscocity and reduced flow in too cool dino fluid. Synthetic viscocity is virtually unchanged when it's cool.

Bottom line, heat is your enemy and the first failure is usually the torque converter which dumps clutch material into the entire system when it fails. Normal torque converter slippage is THE major contributer to high fluid temperatures. A means of keeping your torque converter locked during periods you are towing in mountain roads where you must slow down, shift and accelerate after turns can be a big help in reducing fluid temp. The after market exhaust brake installed on my Ford gives me the option of programming when my torque converter locks and at what speed it unlocks. When towing my trailer I set the lock speed at 35-40 MPH and it will not unlock until I get below 20 MPH. That not only makes the exhaust brake more effective at slower speeds but it prevents the constant locking and unlock cycles the unit computer is asking for. I have the power to pull the load without the TC unlocking and this device allows me to use it while keeping the tranny 50% cooler than it would normaly be if I let the PCM make the decisions on TC function.

Larry