Trying to make transmission lines. My old ones are so bent in the wrong places I cannot tell. I’m wondering, the top line to the trans connects to the top of the radiator right? And the bottom of the trans line connects to the bottom of radiator then?

 

It doesn't matter. It's just circulating fluid through the cooler.

GD

 

GM did run top to top and bottom to bottom.

 

If you can determine which one is the "cooler in" line and which is the "cooler out", hook it up so that the one that delivers fluid to the cooler, is at the bottom; and the one that carries cooled fluid back to the trans, is the top. That way it's self-bleeding.

I strongly suspect (for obvious reasons) that that's how it was originally.

 

Contrary-wise..... I have installed many an external cooler with absolutely no regard for which side got hooked to which port and have never had a single issue with temps reading weird or air locks in the fluid lines, etc.

It's a bit like an incandescent light bulb. It's going to flow either direction and it's going to radiate heat either direction it flows.

One could imagine the number of these transmissions that GM built. Further one can imagine the number of GM trucks that were then equipped in the aftermarket with auxiliary external coolers. Now if we further imagine a world wherein an incorrect flow direction was possible AND detrimental....... two results. It would likely already be the case that you and everyone else would know about it - every cooler sold would come with DIRE warnings, and there would be a LOT of blown transmissions because some idiot hooked up the cooler backwards.

But fortunately any idiot can hook it up and not destroy his transmission. Because it doesn't matter in the real world.

GD

 

"Dire" seems a bit extreme.

Designing in accordance with the natural behavior of the physical world however, is just plain common sense. (not that "common sense" always interferes very much with "design"...)

 

The cooler manufacturers would be scared of being sued. And thus DIRE warning labels and leaflets in the box/instructions, and probably stickers OVER the cooler ports.

For the simple purposes of running hard lines and not having them cross over themselves needlessly it does seem prudent to just let the top go to the top and the bottom to the bottom. I paid no attention when I did my braided AN lines on my Blazer though. The hard lines were completely F'd by the previous monkeys that had owned and/or "wrenched" (loose term) on it. I ran them as was most pleasing and most convenient for them to not interfere with any moving parts.

GD

 

Wouldn't it make sense from a thermodynamic perspective to have the hot fluid enter at the top and the cooler fluid allowed to exit below that? This is in reference to the engine coolant radiator with the integral transmission cooler within which is how I've interpreted the OP's post. Thus, top to top, etc.

FWIW, I have no idea which line leaving the transmission is "out" or vice versa although it wouldn't be difficult to find that info.

AFTT, when I plumbed my own external cooler, I believe I proceeded as GD has suggested without regard for orientation although my cooler is mounted with both lines "up".

 

Wow, that's the sweetest aftermarket solution I've ever seen!

 

Thanks.
I could have gone one better and eliminated those two couplings but I had to use my cheapo big box store multi-head tubing bender. As such it was difficult to nail the back to back to back 90 degree bends. So I cheated a little.

 

According to monster transmission, it should be bottom transmission coolant line to the top of the cooler.

 

Well Monster Transmission is wrong, the pump isn't going to be hurt by pushing the fluid from the bottom of a stock radiator trans cooler.

 

It may not hurt the pump but adding extra pressure increases heat. If you're trying to help the transmission survive, its better to eliminate as much heat as possible. I just dropped a 400hp engine in my camaro and the 700r4 is toast now. I'm having the transmission rebuilt and I'm putting a temperature sensor with an external cooler. The monster video is what I needed to figure out which line I should run the fan switch on.

 

Half the reason the radiator cooler exists is to increase heat. If you want extra cooling capability, put a thermostatic bypass cooler in series after it.

 

to add heat?? It's meant to keep it from getting too hot. I mean, if you're just idling in park, I guess it would add heat.
you do know the function of a radiator, correct?

 

In this case, it adds heat to the fluid in colder starts so it's up to temp sooner. 175-225° or something like that.
Once it's at temp it's pretty much a wash with rad temps.

 

Radiator heats up long before the trans does. You want your trans fluid to get up to operating temp because it works best up there, so the radiator cooler adds heat until the temps equalize. I've never seen my trans get hotter than coolant temp but I do run extra coolers.

 

What are your transmission temperatures?
I'll be adding a temp gauge to my fresh 4L60 so I can keep an eye on it. Especially on track days where I've often made several back to back to back 1/4 miles passes. That builds a lot heat. Now so more than ever with the new higher stall converter.
Curious as to what you're seeing.

 

I have seen up to 175f in the truck ('99 4L60E) during stop and go in the city on a hot day, the average fully warm driving around temp seems to be 156f. I don't have a sensor in the 700R4 but a t56 is going in if that trans needs work.

 

175 is less than I had thought but then again, there's sure to be more when there's racing action.
That's something I'll need to research and find out what the threshold is. I've too much invested in this latest unit (and that's not counting the one before this that are itself up $$$) to let it burn up.
Thanks for that.

 

The truck has a 180f thermostat, so it seems like the radiator cooler normalizes the trans temp to the coolant temp and then the external cooler drops it by an extra 20f or so. At least until you add more heat than the system can shed.

 

From the service manual that came with my 4l65e. Which is essentially a glorified 700r4, right. I think the lower line went to the top fitting on the rad.

 

In a way, yes... 4L60E is of course a 700 except w electronic controls in addition to hydraulic, and the 65 has the 5-gear planets.

Makes sense that they call out for the fluid to enter at the bottom of the cooler and exit at the top, since that makes the whole system essentially self-bleeding. Thermodynamically it makes little to no difference which way the fluid in the cooler flows, since there's always pump pressure moving it, and if the pump doesn't pump, then, ... nothing is going anywhere anyway and it doesn't make any difference whether gravity assists the flow or not since it's about to be on a hook anyway. Not the same situation as coolant in the radiator from back in the Spanish-American War days when belts only lasted acoupla months and failed frequently, making that part of the cooling system "fragile" and in need of whatever backup it could get.

Since the trans fluid cooler is in the cold side tank, the coolant temp there will always be somewhat below thermostat temp, to the extent that the rad cools the coolant. So in the winter, when the air passing over the rad is very cool and coolant flow is restricted to much lower than full capacity by the thermostat, the coolant in that tank will be very cool, and trans temp should be correspondingly cool; whereas on a hot summer day with the AC going and all that, the thermostat will probably be more nearly fully opened, meaning coolant will flow through faster, and cooling by the air over the rad will be less, meaning the fluid in the cool tank will not be cooler than thermostat temp by nearly as much. Engine cooling of course is the same, since a small amount of fluid moving slowly and getting cooled ALOT (winter), results in the same amount of heat exchange from coolant to atmosphere, as a large amount of coolant flowing fast butt only getting cooled by a few degrees (summer). The temp of the castings, and therefore of the fluid exiting the engine toward the rad, is the same regardless, butt the temp in the cold side of the system can vary greatly. In my truck for example (entirely stock setup), the trans gauge may show no more than 150° after a half-hour of driving if it's below 0°F ambient, butt shows 190° or so when it's 100° out. Those are merely the temps in the cool tank of the rad under those conditions. The transmission (4L65E) works exactly the same either way except that the TCC doesn't operate until about the temp where the stock trans temp gauge just begins to move, maybe 100° or so if it can be believed at that extreme of its indication range.

Trans fluid needs to be at a temp of around 160° for the various additives in the fluid to do their thing fully. Temp above 225° or so starts to make the fluid become very acidic which eats clutch material, bushings, etc. over time, as well as making it break down and turn to brown gunk; for that reason the trans temp ideally should never go much above 200° if possible. Optimum trans temp is somewhere in the 180° range, which is why nearly all of the aftermarket thermostatic cooler control valves are set to somewhere in the range of 160° to 185°.

 

while we are talking transmissions, I'm curious about a Toyota Transmission myth. The myth is don't change your fluid 100%. Change in 2 qt intervals every few years. for some reason, people think a 100% trans fluid change is a bad thing. Any thoughts on that?

 

Crappy transmission.

 

Never heard that one. A first for me.

Well I'm sure you've seen my opinion about the importance of THAT.

We have a Lexus LS430. Toyota, Lexus, same thing Japanese, right?


Service manual calls for replacing the transmission fluid every 60,000 miles. Can't answer for what people think.

 

BTW, ours has 280,000 miles on it... no idea whether it's original or when the fluid was last changed... it may be crappy butt the 65E in my truck only lasted about 270,000... of course I never changed the fluid in it, so there is that...

 

I like today's version of Sofa. Kind of easy going, not so angry at the world, and posting funny video clips that prove his point quite well and make us all smile and nod in approval. Almost makes me less angry at the world too.

 

now who are they and what did they do with the real sofa?

 

FWIW I ran my lower trans port to the bottom of the radiator cooler, then the top radiator port goes to an external trans cooler which then comes back to the transmission thru the top port. I believe my 92 k2500 with a 4l80e and factory aux trans cooler was routed the same exact way before I redid the cooler and lines last year

 

I'm guessing you have a V8 and its also older?? But you are sort of proving their myth. We had a ES350 with the ubiquitous V6. I flushed the tranny at 140K and sold it at 190K and never had a problem with the tranny. Which disproved their point. These guys are all worried that if you do that, tranny problems will occur in short order. I also used Valvoline instead of Toyota fluid, which sets their hair on fire.

 

Not sure about "older"; but yes, it's a V8. The 4.3 (= 430) specifically. 2003.

Ah yes, the old "new fluid destroys the transmission" myth. It just won't die. The reality in my experience is, most people don't even think about their transmission AT ALL, until it starts to screw up somehow; slipping, weird shifts, heat, whatever; then, they're like, guess it's time to do some maintenance; so they change the fluid; butt the transmission is already wore out, so changing the fluid at that point accomplishes very little if anything, and it continues to circle the drain ANYWAY; presently it finishes dying; and the myth that the new fluid killed it is born. And without ANY empirical evidence or ANY other data or underlying facts or even tearing it down and LOOKING AT IT to see what ACTUALLY went wrong, they make up stuff about "new fluid ate the clutches" or "clutch material in the old fluid was all that was keeping it working" or similar mythical made-up mumbo-jumbo GARBAGE.

In reality, ANY/EVERY transmission will only last just so long, before some critical rubber part ceases to seal or some clutch's friction material wears down to some critical level or some hard part (*cough* sun shell *cough*) fails from constant bending and vibration or whatever else dies. Any/all will eventually reach this point, no matter how "heavy duty" they are or whatever else. Which is why a 4L80E doesn't really last any longer than a 60E on average, or a Turbo 400 longer than a 350, barring raw abuse and tearing it up; the basic materials aren't any different to begin with. New fluid doesn't change that, except to the extent that its lube and other properties tend to deteriorate over time, which is why it should be changed occasionally (whatever the occasion might be). Keeping good fluid in one might delay the inevitable failure somewhat butt it's not going to completely avert it, nor will it cause failure.

 

Excellent description of how the myth is generated. I'm pretty sure back in 2003 Toyota has fluid change recommendations. But jump to 2010 or so, and I think they are recommending something different. Not exactly sure what it is, I am curious to go find out now. Pretty sure Toyota says transmission is sealed, and does not require fluid change.

 

@sofakingdom Here is what these guys say they recommend doing on a partial fluid change on an older transmission because: "It is gentle on the aging transmission as you only replace part of the fluid so the circulating clutch particles are not all removed at once.

It appears their thinking is that older clutches need the friction of the worn clutch material and if you did a complete removal of that friction, things can go bad.