My apologies if the research I did on "back posts" in here covered my exact question - and I failed to spot it. here's the background. I have one of the very last Excursions made (0ct. '05). ( V-10 4wd). I bought it new and have kept it pretty much mint. We now have about 60,000 trouble-free miles on it. It is rarely outdoors, 'cept when it is being used what we bought it for - pulling our car trailer ( approx. 10,500 lbs) back and forth from the high country of northern Arizona across the Calif. deserts to Los Angeles, or pulling our 11,000 lb boat and its trailer back and forth to Lake Mead and Lake Powell. In summer, we are typically dealing with temps of 100 + - sometimes, coming up the "Kingman Grade" from Needles, Calif, 110 +. I try and "manae" the transmission so that I never get over 3,000 rpm. Each time we start out with a cold motor, both the trans. and engine temp. dash indicators climb slowly to the "center" position, and stay there. Never move any further towards the "hot" position. I know..I know...I have seen posts in here that some of you guys add after-market gauges - havnt done that..yet. No evidence of overheating - fluids for eng. and trans. oil stay clear. Mine dosnt leak or need a drop of fluid. Of ANY fluid. O.K..so my question is - is the Ford V-10 cooling system THAT competent that this vehicle is simply incapable of over-heating ? Dosnt the fact that my trans and engine oil stays clear suggest I am not "cooking" it ?

 

I've driven that many, many times. In Yucca you'll pass the former Ford Desert Proving Ground, now owned by FCA. I've spent many a summer week there.

That's not doing any favors for the transmission. It's easier on the trans at high RPM, the trans works harder at low RPM.

These are not true gauges that are directly connected to a temperature sender. The sender feeds temperature data to the dash computer, which then decides where to position the needle for each of the gauges. I'm not familiar with the engine gauge, but I am familiar with the trans gauge.

The trans gauge will set right in the middle any time the transmission is warmer than 50F and colder than 230F. At 230 F it will go to yellow, and at 260F it will go to red.

Yes it does. If the gauges both stay in the middle you can be confident that you are not overheating either the engine or transmission.

Many people say anything above 200F for the transmission means it's damaged from the heat. That's nonsense. If you're under 230F trans temp you are not going to hurt the transmission.

 

Thanks so much for your response - sounds like you know what you are talking about ! Specifically, thank you for confirming my belief that by noting my oil and trans fluids don't show signs of "cooking", I havnt been abusing my EX thru over-heating.


Only thing that puzzles me is your comment about engine rpms and transmission loads. Let me give you more detail, so you can tell me if my assumptions in that respect are valid ( let me caution you I am from a generation when we still had in service some older motors that were "red-lined" at about 900 rpm - anything over that pretty much guaranteed a rod coming thru the side of the crankcase.....!).


May I assume if I keep the rpm over - say 1,500 - 1,800 rpm I am not "lugging" it ? I try and operate my engine/transmission combination so that I don't have to use more than around half throttle. When I manually select a "lower" gear, be assured I take my foot OFF the gas when I do that, so that the transmission dosnt have to "do its thing" under power. Hopefully, that isn't abusing anything?


Yes, I am aware that my transmission temp. guage can move all the way over - only saw that happen once. When I first bought it and first tried to pull a major grade with it. It all happened so fast. Happened to notice out of the rear side mirrors a huge cloud of Los Angeles smog right behind us. Trouble was, we were just pulling up the grade out of Prescott..!


Then the dash lit up like a Christmass display. And yes, that trans. temp. gauge pegged. Then we slowed down.... Then we came to a stop.... Seems I didn't get all the parts I'd paid Ford for when I bought the Ex....!. Seems someone left off a clamp on an oil cooler line. Turned out to be a very expensive clamp for Ford - (they were very nice about it - no fight over the warranty - was pretty obvious...!) three cheers for AAA's "flat-bed" towing service.......!

 

The V-10 makes its power around 4300 rpm. I routinely spin mine up that high in 2nd gear going up any significant grade. The warmest I've seen my engine coolant temp is 205. The trans temp at the same time is right around 185. Im running the Dash Command app on my Iphone6. I'm towing a 9200lb 11.5 foot tall TT. It hasn't complained once in the 87k miles I have on it!

 

The transmission will be happier spinning a higher RPM since it strains everything less, as opposed to trying to force it to deal with the load at a lower speed. Mark is far better off at explaining it so it makes sense, plus he's our resident transmission guru considering he was a Ford trans engineer for almost 20 years.

In terms of engine speed, you're not in a diesel - the V10 likes to rev and makes its best power beyond what my 7.3 red lines at... Rev the sucker, at 1800-2000rpm you aren't even getting into the power band of the engine so you're lugging the thing anyway. You won't even have enough port velocity at that low of an RPM in the intake to get the engine spinning where it wants to and does the best.

Regarding gauges, the factory setups work quite well for an assurance that things are ok. Some of us have older models that didn't have them, or have starting adding power goodies so we need to monitor other things - the latter is primarily us diesel folk. A different plus to the aftermarket gauges or monitoring is you get an absolute number for temperatures instead of a needle that stays in the 'safe range' in a stock gauge as long as things are within OEM set parameters.

 

No, that isn't lugging the engine. You can't lug a transmission, and I was only addressing the transmission question.

Lifting off the gas when downshifting isn't abusing anything. I don't think it is helping anything, either, but I know it isn't hurting it.

At low RPMs the torque converter is more likely to be unlocked. This generates A LOT of heat. At high loads and low RPM the converter is slipping several hundred to over 1,000 RPM (don't worry, it is designed to do that) and that generates even more heat. At high RPM the converter slip is much less, and the converter clutch is more likely to be on which lowers converter slip to exactly zero.