Where to install the transmission temp sensor is one of the most frequent question and discussions I have with guys. My question to you guys is this, why are you buying a gauge?

If you are buying a tranny temp gauge just so you have one and you can tell your friends you have one then you can pretty much put it wherever you want, as it really doesn’t matter in that case.

To me, a gauge is there to monitor tranny temps and indicate how often to change the oil. If you want a gauge for what I consider to be its primary functions then lets look at the oil. Oil temp is what we are trying to monitor so keeping that in mind lets look at the common places people install their gauges and what they are learning by doing so. Decide for yourselves where you want to monitor your tranny temps from and at what cost.

First lets deal with when and why tranny oil gets hot. Most will agree that trans temps are the hottest in stop and go traffic when the transmission is in first or second gear or in the reverse position, in most cases when trying to back up a trailer.

One of the favourite locations by people is the front servo on the passenger side of the transmission. The problem with that is there is no oil in that port in first gear, 2nd gear, or reverse so what are you measuring?
If you do have a transmission temp sensor in that port, take it out, not only is it not monitoring your oil it is probably causing damage to the transmission as the probe is most likely making contact with the servo spring.

Middle port passenger side better known as accumulator port is another, while this port does measure transmission temp in first, second, drive and od, it is measuring stagnant oil. It other words oil fills up and stays there. There is no oil present in the accumulator while you are in the reverse position. So it is useless to measure from this location also.

Another favourite place is in the reverse port on the passenger side. This port only has oil in the reverse and manual low positions. This means no oil in the in the drive position. I have had guys phone me arguing with me that they are seeing temps of 200 degrees while driving down the road in stop and go traffic when measuring from this port. My comment to that is congratulations we now know the temps of your tranny case, we can only guess at this point what your tranny temps are.

As far as I am concerned, there is only one location to accurately measure your tranny temps from. That is your transmission cooler outline. I have seen temps get as high as 300 degrees coming out of that line. That line sees every 20 seconds 1 quart of oil pumped through it at 1100 rpms. 3.8 gallons at 2100 rpms every minute, in 3 minutes you have pumped out basically 12 gallons of oil. So lets say you see temps of 300 degrees from this line and you have pumped it through your tranny At this point in time you can change the oil in your tranny or you can wait a little longer and change your tranny , rest assured you will be doing one or the other. I don’t make any extra money selling you guys the Chrysler lines, I give you the number we use, 5011244AA. The 1995 and earlier trucks it is a little more difficult to hook up the tranny temp gauge, but the 96 and later trucks you guys only have one choice, use the Chrysler line if you tow and want an accurate reading. To me, a gauge is there to monitor temps and indicate how often to change the oil. Since this is about a 3rd gen truck we purchase the line from one of our dealers Mass Diesel 1-508-660-7093, known as Scott to some of you as there is nothing from Chrysler and Scott did if first.