Transmission Temperature Gauge

[Keith Wire]

Hi Bill,

I sent a note to Todd, but I'll ask you as well. I have a 2007 Explorer with the 4.6 V-8 and the 6 speed transmission. I find that I have trouble telling which gear I'm in and when it shifts from one to another. It is pretty smooth at shifting. I can watch the Tach, but I would like the Interceptor to show the Trany Temp and the actual Gear it is in. That way I could tell if it is "searching."

Do you know if it can, or is there a better way?

Thanks, Keith

[Bill]

Keith -

The short answer is, I don't know.

The gauge can read out whatever parameters are put on the OBD-II bus by the various computers in the vehicle. This means that the list of parameters is similar in various vehicles, but not identical. I spent a long time searching the Internet for the parameter list for my '02 Explorer - never did find it. Todd assured me that it could read tranny temp, which is what I really wanted, so I went ahead with the order.

In the case of my '02 Explorer, info on the selected gear is NOT available. In a similar vein, I was hoping that I would find an indication of whether the torque converter is locked or unlocked (unlocked = heat!), but that is not available either. Both of these pieces of information are generated by the transmission and used by the power train computer, but apparently they are never put on the OBD-II bus.

Let me know what you find. The new Fords have a much more advanced OBD-II bus, and I wouldn't be surprised to find that it carries much more information than the one on my 5 year old Ford.

Bill

[Harry Womack]

The new Tahoe and Suburbans do not have an aux. transmission cooler unless you order the 4.10 rear end. Also they feed the transmission fluid thru the radiator backwards (from bottom to top). This brings the oil in on the cool bottom of the radiator and exit on the hot top. I was pulling my 3124 over Monarch pass in CO with the outdoor temp at 55 degree and light rain. The transmission temp went to 240 degrees. I added a large cooler since then. I pulled a heavier trailer last week and my temp. never went over 200 degree.

[Bill]

Good info, Harry, thanks for posting it. The Tahoe is a big vehicle, and the Suburban is even bigger. One might be tempted to conclude that they have plenty of cooling capacity just as they come off the showroom floor. As you have experienced, this is not necessarily so.

Every vehicle with an automatic transmission has a transmission cooler (looks like a small radiator) mounted in front/back of the radiator. Or it may actually be built as part of the radiator. Either way, this is the main cooler, not an auxiliary cooler. There have been so many posts here saying "there is a cooler mounted at the radiator, so I guess I'm good to go" that I have given up straightening them out. Once again, NOT SO!

For tough towing situations, such as the one you describe, an aux cooler can be really important, as well as a temperature gauge (glad I finally got one!)

Bill

[fcatwo]

There are two considerations when increasing the automatic transmission fluid (ATF) cooling capacity with an auxillery transmission cooler. One is that we may need extra cooling when towing or simply operating in extremely hot weather or mountain driving. The second (and reverse consideration) is that we should't super-cool and thicken the ATF in cold weather. This second one is possibly why Chevy routes the ATF to leave the warm part of the radiator rather than the cool. In the old days people with after-market ATF cooler equipped vehicles covered their auxillery trans coolers during cold weather and uncovered them when it warmed up. The manufacturers likely feel they can't rely on us to do that sort of thing anymore and design their vehicles accordingly -- that is to handle most situation but not the extremes.

There are aux trans coolers on the market that are large enough to cool in hot weather but can also solve the cold weather problem by restricting the flow of the ATF until it warms up. There is probably discussion of those here somewhere.

[Harry Womack]

The cooler I put on is regulated, it only cools the oil if it is hot. The transmission with dextron VI oil smelled like hot brakes at 240 degrees.

[mjlaupp]

An alternate method of installing an auxiliary transmission cooler is to place it between the transmission and the radiator so that the fluid leaves the transmission, flows first through the auxiliary cooler, then through the internal radiator cooler and on back to the transmission. This way the "super-cool" transmission fluid is reheated in winter.

Got this from an "old days" installation manual, vintage 1962 or thereabouts.

Mike

I added an external trans cooler to my 1971 Chevy 4x4 truck that I had purchased used. I was concerned about towing a motorcycle trailer with 4 dirt bikes in the Nevada desert in July. As I recall the instructions were that the cooler external cooler was before the radiator cooler for just this reason. This was in 1979.

[Harry Womack]

The aux. transmission cooler should be after the radiator cooler. All instructions with aux. cooler say to check flow direction to make sure it flows thru the aux. cooler last. The reason is the thermostat on the engine is set at over 200 degrees. Why run transmission oil thru an aux. cooler and the run it thru a hot radiator to heat it back up before returning it to the transmission.

[fcatwo]

I don't disagree with Harry in priciple but there are exceptions to every rule. I've owned three vehicles with auxillery ATF coolers and all were installed downstream from the radiator. I covered the first one in cold weather however and the last two were factory jobs that were/are much smaller than I would install after-market. Having been in Fairbanks for a few days in January I can assure you that the world is a different place at -50 than it is at +50. IMO the after-market, temperature-sensitive coolers like Harry installed are the best way to go if a TV doesn't already have one.