# Tranny Temp



## fshr4life (Feb 7, 2009)

I just thought I'd pose the question and see where you start to feel uncomfortable with your transmission temperature. We went camping in upstate NY this weekend and on the way back, I climbed a 2-mile stretch of highway at about a 7.5% grade at 55-60 mph and my tranny temp went up to 210 degrees. It was running between 185 and 200 degrees on the highway at around 60 mph. I spoke to a friend who is an automotive engineer and he said that it's nothing to worry about. Your thoughts?

JD


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## Calvin&Hobbes (May 24, 2006)

There are far more experienced minds on here than me, but I recall that if it is below 215/220 your OK. Above that, the viscosity breaks down with rising temp/time. Do you have a tranny cooler (other than the bottom tank of the radiator)?
http://www.txchange.com/heatchrt.htm


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## jcat67 (Aug 8, 2008)

I spoke with the service department at the local Chevy dealership asking just that question about my Silverado and they told me not to worry until 260. I have been in the area of 215, but nowhere near that.


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## johnp (Mar 15, 2004)

Too hot is when you blow 2 quarts out the vent tube and all over the front of your new trailer







that was too hot and too expensive.One more 4L60E roasted.

John


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## battalionchief3 (Jun 27, 2006)

That temp per the dealer is OK, for short trips, once and a while. You saw the link in C&K's post so realize that heat kills a tranny. Now if GM didn't change the transmission ( and i bet they didn't ) its still the 4L60E. If it was my truck I would upgrade the cooling capacity of the transmission.

http://www.bmracing.com/PRODUCTS/Hi-Tek-Au...-Cooling-System
http://www.mag-hytec.com/

I have both of these products and they work. The transmission cooler from GM is sad at best, it was about 12 X 6 and thin. Look at cooler I got and its 5 times the size and the pan holds more fluid and dissipates the heat faster. I also ran at 200 on flat ground but 215 up grades in PA. Now I cant get about 175 and hold 20qts ( 5 gallons ) compared to a stock unit of about 12 to 14qts. I'm my opinion up grade and go big, your tranns will thank you.


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## fshr4life (Feb 7, 2009)

Calvin&Hobbes said:


> There are far more experienced minds on here than me, but I recall that if it is below 215/220 your OK. Above that, the viscosity breaks down with rising temp/time. Do you have a tranny cooler (other than the bottom tank of the radiator)?
> http://www.txchange.com/heatchrt.htm


Great chart. Thanks! I've got a tranny oil cooler built in as part of my towing package. I was reading on some other sites that the tranny cooler on the new chevies is buried under a stack of other radiators, so it doesn't cool really well unless you're moving. There is a mod that some folks do to move the tranny cooler out of the stack and out in front of the others. I would think about it, but I don't really want to void my warranty right now! Another guy on the site I was looking at said to turn the AC on because it has a fan that helps pull more air through the radiator stack. I might try that next time and see if it makes any difference (besides robbing you of some towing power). That being said, I was close to home and wanted to see how well my truck could accelerate up the hill, so I was pushing it a little. I didn't have any problems with power, but the tranny temp started quickly creeping up. That's why I was curious.


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## jolarsen (Apr 10, 2006)

I have a 2007 2500HD,6.0 pulling a 26RKS. My tranny temp stays around 170 to 180 on occasion it might climb lil higher but not much. I will be pulling down to Little Rock AR and back up thru Branson MO and back to KS next week so I am excited to see how it does in more hills. I have put some MotorMaxx in my antifreeze which is a cooling agent. It has kept my engine approx 15 to 20 degrees cooler whichin turn should let your tranny run cooler. It helps with my a/c cooling too(cooler engine). The other amazing thing is it warms it up faster. Im a true believer in the company that makes this product cause Im on a volunteer fire dept and we use ColdFire as our foam in our fire engines. The codfire is amazing stuff so I figured MotorMaxx should be good too and soo far I like it. By the way i dont sell the stuff im just a user of it and a believer in it. if you want more info let me know I can call you or something...Take Care All

www.firefreeze.com


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## Sayonara (Jul 23, 2007)

220 was the number i always used as a limit. it got close a couple times on my F150 but never over.


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## fshr4life (Feb 7, 2009)

battalionchief3 said:


> That temp per the dealer is OK, for short trips, once and a while. You saw the link in C&K's post so realize that heat kills a tranny. Now if GM didn't change the transmission ( and i bet they didn't ) its still the 4L60E. If it was my truck I would upgrade the cooling capacity of the transmission.
> 
> http://www.bmracing.com/PRODUCTS/Hi-Tek-Au...-Cooling-System
> http://www.mag-hytec.com/
> ...


We're going to make a trip down to PA later this month, so I'm going to see how it does in the mountains there. We came back through eastern PA on our way back from Lakeshore when we first got the trailer and the tranny never went above 204 degrees even climbing the mountains there. Of course, it was also about 40 degrees outside then. If it looks like it's getting too hot on this next trip down there, then I'll look at upgrading to one of the bigger coolers.


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## azthroop (Jun 16, 2007)

I copied Battalion Chief and added a B&M tranny cooler with a large additional fan. I also added the larger tranny pan, too. I can now run up some serious grades and once it hits 200 degrees, the fan kicks in and drops it back down to 175.

The cooler you can keep the tranny, the longer you will have it!!

azthroop


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## California Jim (Dec 11, 2003)

A couple of things about tranny temp:

#1 The factory gages can be extremely inaccurate. The worst my tranny guy saw was off 60 degrees. 
#2 Were is the gage getting it's information from? In the pan? In the outlet/hot side of the tranny line? On the cooler tranny return line?

There are variables that you first need to determine before you can then correctly consider your cooling performance and heat being generated.

The factory gage on my 2007 Suburban is reading the temp from the hot/outgoing line on the tranny and can reach 230 degrees climbing a big mountain on a hot day. However the fluid temp in the pan is 30-40 degrees cooler. Just FYI, the pan temp is what most tranny guys will tell you is the most important reading. There may be some disagreement about this, but consider my example. If I modified the cooling system to be reading no more than 180 or so when "hot" then my pan temp might only be 140. I believe that may be too cool.

A quick visit to your mechanic armed with an infrared beam can soon tell you where your gage is getting it's info and if it's accurate.


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## battalionchief3 (Jun 27, 2006)

Jim is correct with his statement.
Also when I got my tranny worked on it was winter and it took over 20 miles for the trans to warm up to a normal operation temp because the ambient air was so cold. Try it in the hot summer with high humidity and see how it does. I would still replace it. My suburban has a tow package with an "external cooler" and like i said it was a joke. I also noticed my 08 suburban at work with a tow package has the "cooler" buried in a stack of stuff and thats the wrong answer, it needs to be out front and big to get air and do its job with or without a fan on it. Off road desert racing or rock crawling is testimony to big coolers and fans.


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## fshr4life (Feb 7, 2009)

I looked at my tranny cooler today and you're right, it's not very big. However, it is out in front of the radiator and not buried as I read on a post on another site. I guess they made that change from 2007 to 2008. The good news is that there's plenty of room around it and it's easy to get to, so it should be easy to upgrade. I'll take Jim's advice and try to figure out where the temp sensor is. I've got a remote infrared thermometer, so I'll run the tranny and get it warm and then see what temps I'm getting off the pan and other locations to try to figure out where my sensor is mounted and how accurate it is. I'll try to do that this coming weekend.


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## fshr4life (Feb 7, 2009)

California Jim said:


> A couple of things about tranny temp:
> 
> #1 The factory gages can be extremely inaccurate. The worst my tranny guy saw was off 60 degrees.
> #2 Were is the gage getting it's information from? In the pan? In the outlet/hot side of the tranny line? On the cooler tranny return line?
> ...


Jim, you were right on the money. I heated up my Tranny to 167 degrees according to my dashboard temp guage (it's a digital readout). I then stopped and measured the temperature of the tranny oil pan with an infrared thermometer and it only read 130 degrees, a difference of 37 degrees. I then measured the back of the tranny outlet and got 167 which is exactly what the dash guage was reading. My conclusions are that the temp gauge in my truck is accurate, but it isn't located in the oil pan, but instead on the hot outlet side of the tranny. That's good news. If the 30+ degree difference always applies, my tranny fluid in the pan was really only at about 175-180 when I was climbing that hill. I'll try this again when I'm towing and have the tranny a little hotter to see if the same temperature differential applies.

JD


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## battalionchief3 (Jun 27, 2006)

Good job on the research. You would think they would have put it in the pan or at least on the return from the cooler side. Who cares how hot it is leaving the trans, its leaving to go cool off. The pan is where the pick up is and thats the spot you want to know because thats going into the trans to absorb heat and do the work. I still recommend a bigger cooler, it allows more fluid and faster dissipation of the heat.


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## fshr4life (Feb 7, 2009)

battalionchief3 said:


> Good job on the research. You would think they would have put it in the pan or at least on the return from the cooler side. Who cares how hot it is leaving the trans, its leaving to go cool off. The pan is where the pick up is and thats the spot you want to know because thats going into the trans to absorb heat and do the work. I still recommend a bigger cooler, it allows more fluid and faster dissipation of the heat.


 I have been reading about this on some other sites and there is a lot of controversy about where a temp sensor should be located in a tranny. It seems that most folks think that the pan is the best location since it give you the average temperature of the fluid that is being sucked back into the tranny for cooling and lubrication, while others believe that having it in the hot return line tells you the max temperature that the oil reaches and therefore helps you deteremine if you're at the point where the oil is starting to break down. Others argue that the temperature is only that hot for a few seconds because, like you said, it's going to be cooled, and so the oil isn't really going to start breaking down at that point. Then there still are others that say that the sensor should be in the cool return line to help you determine how efficient your oil cooler is. I see the logic of all three, but I think that the cool return line would probably tell you the least about the state of your transmission. Apparently Chevy decided that the hot return line (or at least somewhere close to it - I didn't find the actual temp sensor yet since I only took a couple of minutes to do the measurements after work today, but I'll keep looking) was the best place to put it in this case. 
At this point, my only concern with installing a bigger cooler would be over-cooling the tranny fluid in the winter around here. It gets pretty cold in upstate NY and the ATF needs to be warm to function properly. I use my truck as a daily driver in addition to towing, so it usually doesn't have a heavy load behind it. That being said, if I find that I need it this summer while I'm towing, I will definitely install a bigger cooler and then if necessary cover it and/or unplug the fan in the winter months.


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## fshr4life (Feb 7, 2009)

I spoke to my friend who is an automotive engineering instructor and he told me the following things:

1. Temperature sensors are installed by a car company to trigger a fault, not necessarily to give the driver information. In order to trigger a fault for the transmission, they put the temp sensor at the hottest possible location on the tranny which is the outgoing line. This allows the computer to activate countermeasures or put the engine into safe mode when the component starts to get too hot. Normally, they "fade in" countermeasures rather than just shutting down the whole system (a good thing if it happens while you're climbing a steep hill). For example, the computer may do several things such as turn on the cooling fans at some set temperature, issue a warning to the operator, change the shift timing, etc before eventually reaching the point where it puts the engine into safe mode. Safe mode retards the timing and limits the fuel input to the engine greatly cutting your engine output.

2. The outgoing line is the best location for the temp sensor because you want to know how hot the oil is getting, not just the average temperature of the pan. This gives you a better sense of what is going on inside the hottest parts of your tranny (and helps car companies avoid law suits







). Also, thermal breakdown of ATF starts when it gets too hot, so you want to know when that is, no matter if it is only for a few seconds.

So there you go. I guess the tranny sensor is in that location for a good reason.


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## California Jim (Dec 11, 2003)

Good stuff. Whatever school of thought you subscribe to, now you know exactly what's happening and can make an informed decision. I'm confident it will be a good one. Good Luck


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## ohiobmwbiker (Aug 23, 2008)

FYI, Geno's Garage is having a father's day sale this month - 10% off all gauges AND 50% off any gauge mount when purchased with a gauge.

Geno's sells parts for Dodges but the gauges will work with any brand of truck. I just recieved my Isspro Ev2 trans temp gauge for $78 which included the sensor and the grab handle mount for $30. What a deal!!! I also bought the backlight adjustment kit which is really just 3 wires soldered to a potentiometer for ~$25, that was sort of a rip off by Isspro.

John


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## Rubrhammer (Nov 27, 2006)

Consider just adding a pusher fan to the tranny cooler with a toggle switch. No voiding the warranty and you could flip it on prior to going up a grade or at any point when your guage reads higher than what you aare comfortable with. It also will not affect cold weather operation, and it isn't an expensive mod.
Bob


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## Sweathog62 (Jul 28, 2005)

Rubrhammer said:


> Consider just adding a pusher fan to the tranny cooler with a toggle switch. No voiding the warranty and you could flip it on prior to going up a grade or at any point when your guage reads higher than what you aare comfortable with. It also will not affect cold weather operation, and it isn't an expensive mod.
> Bob










Hmmm do you have a link for this type of fan??


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## fshr4life (Feb 7, 2009)

Rubrhammer said:


> Consider just adding a pusher fan to the tranny cooler with a toggle switch. No voiding the warranty and you could flip it on prior to going up a grade or at any point when your guage reads higher than what you aare comfortable with. It also will not affect cold weather operation, and it isn't an expensive mod.
> Bob


I was thinking about doing exactly that. To echo Sweathog, any idea where I can get one?

JD


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## jcat67 (Aug 8, 2008)

fshr4life said:


> Consider just adding a pusher fan to the tranny cooler with a toggle switch. No voiding the warranty and you could flip it on prior to going up a grade or at any point when your guage reads higher than what you aare comfortable with. It also will not affect cold weather operation, and it isn't an expensive mod.
> Bob


I was thinking about doing exactly that. To echo Sweathog, any idea where I can get one?

JD
[/quote]

This makes 3 of us watching and waiting......


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## fshr4life (Feb 7, 2009)

jcat67 said:


> Consider just adding a pusher fan to the tranny cooler with a toggle switch. No voiding the warranty and you could flip it on prior to going up a grade or at any point when your guage reads higher than what you aare comfortable with. It also will not affect cold weather operation, and it isn't an expensive mod.
> Bob


I was thinking about doing exactly that. To echo Sweathog, any idea where I can get one?

JD
[/quote]

This makes 3 of us watching and waiting......
[/quote]

I just found these at JEGS. They've got some 8" fans that look like they would probably work. The Derale Tornado fans on the bottom left say they are the most powerful ones (400 CFM for an 8" fan), but the straight blade JEGS fans pull 375 CFM and cost quite a bit less. I've got to do some measuring to see if one will fit behind my cooler to serve as a puller fan.

http://www.jegs.com/c/Electric-Fans/10117/...CFQOIFQod1w0tdw


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## Piecemaker (Nov 15, 2007)

My $.02 is

I thought my trans was slipping so I had chevy check it out under warranty. When I picked it up they told me there was no slippage and the trans fluid wasn't burnt and didn't smell burnt.

This was good to hear since pulling my tt also the temps have gone up as high as 220 on hot days. One thing Chevy did tell me is that "in the towing mode the trans would shut down when it gets to hot." Not sure if I want to believe this. I sure hope it gives me a warning first.

Any feedback on the Chevy's comment?


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## fshr4life (Feb 7, 2009)

Piecemakers said:


> My $.02 is
> 
> I thought my trans was slipping so I had chevy check it out under warranty. When I picked it up they told me there was no slippage and the trans fluid wasn't burnt and didn't smell burnt.
> 
> ...


 From all the research that I've done over the past several days, I am pretty confident that there are electronic countermeasures in place in a new Chevy that will prevent you from overheating the tranny to the point that you ruin seals, gaskets, etc. Those countermeasures could include the things that I mentioned in my earlier post (a warning message, engine safe mode, etc) BUT you shouldn't rely on that to protect you! You can certainly break down your transmission fluid by running it at too hot of a temperature for too long (at a point below the warning message threshold), and that, in turn, can eventually destroy your tranny.

From what I've read and heard, the seals won't start getting burned out until temperatures of over 260-280 degrees or so, but your tranny fluid starts to suffer at at a point well before that at anything over say about 190. As long as you change your transmission fluid more frequently when you tow (say every 25,000-30,000 miles or so when towing with higher-than-average tranny temps as opposed to every 50-75,000 miles for the family sedan), you should be OK. I have decided that I'm not going to let mine get over 220 degrees and I'm going to religiously change my tranny fluid every 25,000-30,000 miles. If I find that it's getting up to 215+ on a regular basis in the hills around here during the heat this summer, then I'm going to install a bigger tranny cooler to keep it down (or maybe I'll first try just adding a fan to the tranny cooler that I can manually switch on). Otherwise, I'm probably going to run it the way it is and regularly change the fluid before it has a chance to break down.

JD


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## nynethead (Sep 23, 2005)

My brother is a tranny god and has advised me not to worry unless it is going to go over 250. once you go over it's too late.

That of course would be for my Allison, I have seen 210 going up a steep PA grade pulling my 5'er on a 95 degree day.


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## battalionchief3 (Jun 27, 2006)

Thats a fine practice but by the time you flush your trans that many times over the time you have it you could have bought a bigger cooler and pan and NEVER get too hot so frequent changing of the fluid could be avoided. To flush all the fluid is expensive bacause they use one of those flushing machines and a pan and filter replacment only gets you 5 or 6 qts but you get a new filter and the machine type flush does not include a filter change. The choice is your.....


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## Piecemaker (Nov 15, 2007)

First, thanks for replies.

Of course I'm not presently under my tv and can only speak of my own model (2007 Chevy) but when underneath changing oil, I noticed the exhaust pipe/pipes run very close to the trans pan.

Question is: If a deflector of some sort such as a cat shield were placed between the 2 (trans pan and exhaust) would that help keep the temp down and cool it faster when driving?

I had thought of wrapping it at first with a motorcycle exhaust wrap until I saw a sensor in the exhaust pipe.

Any feedback appreciated.


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## fshr4life (Feb 7, 2009)

Battalionchief - you make a very good point on changing the tranny fluid. It is expensive, but if you're towing, you should change it regularly anyway. Like I said, I very well might end up installing a bigger tranny cooler, but I want to tow some more during the summer first and see how it does. The only time it's ever gone over 200 degrees was when I was towing up some pretty long, steep hills and pushing my speed to keep it around 60 mph. If that remains the case, then I'll probably slow down on hills and save my money for something else, but if it starts to run at hotter temps all the time when the weather gets hot and humid, then I'm going to install a bigger cooler.

Piecemakers - My exhaust is the same way on my 2008 Chevy, but the amount of heat transferred from the exhaust pipe to the tranny pan is going to be very, very small compared to the heat generated by the tranny itself. Quite frankly, you probably have more heat introduced by the tranny fluid flowing along the sides of the engine block and through the main engine radiator than by the exhaust pipe being close to the pan (you probably already know this, but the standard tranny cooler is along the side of the engine radiator, so cool fluid gets heated up when it goes through there and cooled down if it gets hotter than the engine coolant - if you have "heavy duty towing equipment" installed on your truck, then you'll also have an additional tranny cooler that looks like a separate little radiator). The exhaust isn't actually touching the pan on mine - it's a few inches away (I'm assuming it's the same on yours) - so heat will only be transferred to the tranny pan by convection and radiation (not by conduction), and the convection will be really limited while you're driving since there will be outside air flowing under the truck. I recommend that if you're worried about your tranny temps, you do what Battalionchief recommends and install a bigger cooler. I wouldn't worry about the exhaust pipe being where it is.


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## fshr4life (Feb 7, 2009)

OK. I just got back from our eastern PA trip and I learned an important lesson:

On the way out, the tranny got up to 215 on one hill, but most of the time it ran about 190-205. That's OK but a little on the hot side. I would rather be about 10-15 degrees cooler. The truck had no problems with power and pulled the trailer up the steepest hills without an issue, but the tranny temps were my concern. The outside temps were in the mid 80's, so not super hot, but we were fully loaded with gear (minus water) and had four adults and a child in the cab. As I was driving, I was closely monitoring the tranny temperature for the whole trip. I noticed that the temp would actually drop right as I started up a hill and then slowly climb as I went up. It would then continue to climb at a faster rate on the descent. Then, when I started the next hill, it would be at a slightly higher temperature than the previous hill and then the process would start over. Over an hour or so, the tranny started to get hot doing this (this is when it got up to 215 on a really long steep hill). Not good! I was considering immediately installing a bigger tranny cooler as soon as I got home.

However, watching this trend, I learned that the best tranny cooling occurs at about 2000-2500 RPMs on my truck. This means that the fluid is pumping the best through the tranny cooler and dumping heat best at those RPMs (at highway speeds). Anything below or above those RPMs and the tranny started heating up. That is why the temps dropped right as I started to climb a hill and then went up rapidly as I decended then other side. When I went up most hills, the tranny dropped down to 3rd and ran at about 2400 RPMs or so. This caused the tranny to drop in temp since it was running in the sweet spot for cooling as I started climbing the hill. Then, when I crested the hill, the tranny dropped back into 4th gear and the RPMs dropped to about 1500. This reduced the cooling capacity and the tranny started to heat up, even with very little load on it on the downhill.

Keeping this in mind, I did an experiment on the way back home. I drove the same way that I did on the trip out with the towing mode on with the tranny in drive (4th gear) for about the first 100 miles. My tranny temps were pretty much exactly the same as on the way out (in the upper 190s and low 200s with occasional spikes into the 210s on long steep hills). I then dropped the tranny down a gear to 3rd and kept it there with the towing mode on. This kept the engine right in the sweet spot on the RPMs, especially on the downhill stretches. This solved the problem! My tranny temps quickly dropped to the mid 180s and stayed there on all but the steepest hills. Even then, they only got up into the mid 190s which is totally acceptable on a steep hill. The key was starting the hill at a lower initial temperature and then forcing the tranny to run at about 2000-2500 RPM on the way down which kept the tranny in the 'sweet spot' on RPMs, dumping the heat on the downhill stretches. On less hilly stretches, the tranny was in the 170s which it never got to on the trip out.

This all makes perfect sense, but I guess I had to learn it the hard way. I know that lots of people tow with their overdrive off to increase torque and reduce shifting, but I learned that there's a little more to it than that. I have a tow mode on my truck and erroneously thought that I wouldn't need to drop down a gear with it on. The tow mode slows the rate at which the tranny shifts, but it still allows it to go into overdrive. In hilly areas, this causes the tranny to shift more than it should (increasing heat) and, more importantly (at least from what I can tell), reduces your tranny's cooling ability on downhill stretches. I think this is fine if you're on flat terrain, but if you start hitting hills or mountains, you might want to consider dropping it out of overdrive to reduce shifting and increase your tranny's cooling ability on the downhill. Once I did this, my truck towed very smoothly and rarely dropped to second gear -- and only then for just a few seconds on the steepest hills. I watched my RPMs more than my speedometer and tried to keep it in the sweet spot. I was running anywhere from 50-65 MPH.

As far as gas mileage goes, I got 10.0 MPG on the way out and 10.6 on on the way back with the overdrive off. However, I had a slight headwind on the way out and a tailwind on the way home, so the verdict is still out. My guess is that I will get slightly worse gas mileage with the overdrive turned off, but we'll see.

JD


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