[QUOTE=HeyYou;3282864]Bear in mind, there is such a thing as over-cooling as well. Trans fluid that isn't warmed up enough is just as bad for your trans as fluid that gets overheated. That's why lots o' folks install a temp gauge, so they KNOW what temp the trans is running at, and can adjust their driving accordingly. You wanna stay between 175, and 225, (though I think the 225 is a tad high..... I would want to stay under about 210....) A rather serious trans cooler, with a thermostatic valve, is one of the best things you can do for your trans.
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I tend to disagree just a bit. Anywhere from 140-200 you're safe. In O/D by the time my trans temp reaches 180 my o/d unit is hot af and cooking my fluid. I get kicked out of O/D and that doesn't happen until 250. Pretty sure I need a new trans but still anything over 120 and below 220 is perfectly safe.

 

[QUOTE=dapepper9;3282945]Then you have a larger problem going on there. I have yet to see my trans temp light come on, and I have done some rude things to my truck. (5300 pounds of dirt in the bed probably wasn't the best idea.) The temp sensor is part of the governor pressure sensor, if fluid at that point is hitting 250 degrees, you have a serious problem. If your gauge is telling you your trans fluid is only 180 degrees, it's entirely possible that it's just the sensor that is lying.

 

I'm not using myself as an example for ideal temp. I'm just using the O/D kicking me out as an example of how much hotter O/D can get, especially if you probably just need a new trans like myself lol. I've never had the light come on but I know it gets hot in O/D if I go over 70 for too long cuz I can smell it.


I have an aftermarket pan with temp sensor port that takes a pretty good reading. I've double checked it against a scanner and even laser thermometer so I know it's accurate.

 

I thought that the Trans Temp light in our trucks came on at 270?

Everyone always says that their trannys heat up once they hit overdrive, but I see the complete opposite. Once that Torque Converter locks up and stops slipping I see temps go immediately down. Again, I have it in the line coming out of the tranny and right into the cooler.

 

An open exhaust doesn't scavenge at all, so it doesn't aid low and midrange power at all.

An exhaust system with interior expansion points, like a catalytic converter, will draw gases toward those expansion points. To get a visual, imagine a bubble of hot gas being pushed down a pipe under pressure, entering an empty chamber the size and shape of a muffler -- the gas expands to fill the void, so both the pressure and the temperature of it will drop. That's the magic. Heat moves toward cold, is the big thing condensed into a short sentence, and higher pressure moves toward lower pressure, so now that gas in that chamber is inviting the exhaust gas bubbles behind it to come on down and join the party.

That's where the fantasy of "needs back pressure" comes from. It's not that the back pressure is a good thing, but that back pressure is associated with the kind of a system design that maximizes exhaust gas velocity. Suppose just for discussion that each bubble has a volume of 80 cubic inches, and it's got a pressure of 100PSI behind it when it clears the interface and is fully within a 1.5" diameter pipe that is our exhaust manifold/header. Now open that pipe diameter up to 3" a little further downstream, and you've got the same 80 cubic inches but it's entered a pipe of a 3" diameter, so the pressure drops to 25PSI or thereabouts (due to the inverse-square law). That gas is going to expand to fill the pipe so it's going to cool and slow. We want exactly that for scavenging to happen. It's not that the back pressure is helping you, but that the back pressure is a component of the overall system that's helping you.

That's also why high zoot racer dudes who've got everything else tuned to max will insulate their headers with insulating tape. They're maximizing gas velocity by preventing the heat loss that would cause the pressure to drop.

Ultimately, a towing rig is happiest with a 4-2-1 (Tri-Y) because it has lots of expansion points very close to the exhaust ports. The next best is the shorty header, which is an exercise in tradeoffs but will get you the next best bottom end power. Long tubes are for someone else.

Go with a high flow cat. It's the next great opportunity for an expansion point.

While it's true that muffler/no muffler/this or that kind of muffler is going to have minimal effect if you've got lots of expansion points upstream of it, and it might not matter to you if you do or don't lose the opportunity for just a bit more help, your towing rig is going to make a lot of noise while it's pulling and that's going to increase discomfort and fatigue for anything with ears in the cab. But if you want to take advantage of the opportunity, select an absorption type muffler, which will also give benefit at high flow rates by reducing the resistance to below that of a straight pipe. But just a little bit. By the time you've got through header collectors and the cat your exhaust gas is relatively slow and cold so you just don't have as much energy to work with way back there.

Oh hell yes tire size plays a role here. The taller the tire the greater the rotational inertia of it, so the more energy it takes to make it turn and the more energy will be stored in it while it's turning, energy that you have to convert to heat in the braking system when it's time to slow or stop it. That diameter is the length of Newton's torque wrench, and it wants to keep that system in balance -- if it's not moving it wants to keep it from moving, and if it's moving, it wants to keep it moving in the same direction at the same velocity. So if you're a guy who wants to make it easier to turn that axle, you want to shorten Newton's torque wrench.

That's why folks who want to go really really fast want smaller diameter torque converters or flywheels. It's easier to think about the flywheel because its only purpose is to store the kinetic energy it got from the crankshaft during the power stroke to give it back later during the intake and exhaust strokes. With no flywheel that engine won't run at all -- it'll make the fires and all of that while the starter is turning it, but there's just not enough rotating mass within the engine to store enough energy to get through those other three cycles so it'll stop right after the starter disengages. So to get maximum acceleration you want to lighten that flywheel to be just enough to keep the thing turning, and because the kinetic energy of it is low it'll make for a lumpy idle and lots of shaking and vibration until the RPM's rise to put more energy into the thing.

Each wheel and tire being another flywheel in the system, you want to minimize their kinetic energy so you need less power to make them turn and less kinetic energy you must convert to heat energy to slow them down. It doesn't seem like it would be all that much, but imagine the difference between twirling a lasso all by itself and twirling that same rope tied around the circumference of your truck tire. The lasso isn't doing anything useful unless it's entertaining someone regardless of whether it's tied around a tire or not, but it takes a lot more energy to do nothing useful with it when the tire's there.

Besides, the taller the sidewall the less resistance it offers to the forces the trailer is returning to the vehicle towing it. That's bad when controlling that energy is what keeps everyone near it alive.

You're conflating two different things there but you're still generally right. The converter dumps waste energy as heat during its torque multiplication mode of operation, when the input is going much faster than the output and the oil is coupling input to output -- there's heat in there because there's friction in there, and if there were no friction the converter would be just a metal donut with no purpose. So when you first hit overdrive you're going to get a big temperature rise, but then when you lock the converter clutch so there's no appreciable friction any more it'll stop generating that appreciable waste heat, too.

If the converter clutch were to never lock, it'd be really very easy to make overdrive smell like smoked ATF.

See above, brother. Dead transmission turnin'.

 

I knew that a year and 40k miles ago lol. O/d unit is just ****ed, rest is fine. I dont use it unless I'm 60mph or higher though too because of it. She keeps turning though lol

 

And let's not even get into reversion pulses...

 

How about tuned length primaries?

 

Thanks to hey you and unreg for some schoolin! I know some of hey you' s background (2 thumbs up) but I gotta ask unreg .....Did you teach auto shop class by day and teach a creative writing class by night cuz I get a kick out of your replies. Keep em coming....

 

You aren't the only one. He is responsible for many a monitor cleaning.