Random question. Transmission cooling.

[lyrikz]

I have a transmission cooler mounted on my radiator and its also plumbed into my radiator. Well, talkin to this old timer the other day and he says i should keep the transmission cooler but not run it through the radiator because that hot fluid in the transmission will cause the vehicle to over heat.

he stated that you pump 240 degree transmission fluid through the radiator and it will cause it to overheat. So i should disconnect it.... Thoughts??

He also lives in arizona if that matters. Sum up, keep the trans cooler, but just dont run the trans cooler AND the lines into the radiator.

Thoughts?

[my67chevytruck]

i have ran standalone tran oil coolers, and ran the tran lines through the radiator for cooling, and never had it cause overheating.

[lyrikz]

Originally Posted by my67chevytruck

i have ran standalone tran oil coolers, and ran the tran lines through the radiator for cooling, and never had it cause overheating.

Ok. It just seemed to make sense to me. Pumping in hot transmission fluid would heat the radiator up. But he also lives in arizona so maybe its an issue there.?

[Fitz]

Originally Posted by lyrikz

Ok. It just seemed to make sense to me. Pumping in hot transmission fluid would heat the radiator up. But he also lives in arizona so maybe its an issue there.?

Nope. I live in Tucson, run a trans cooler fitted in my Rad and have never overheated. In summer here it is not uncommon to see 112-115 degrees.

[Hair]

Really I have never seen what good it does to run the fluid through that enclosed part of the radiator anyway... it can't cool it much.

[eagleuh1]

Run it through both, radiator first then the cooler.

[cdowns]

best to run thru radiator// trannys work better iwith some heat in the fluid in very cold climates in the winter that heat maintained by using the radiator helps save the tranny and allows it run properly

[Richard H.]

US vehicles were and are designed to be in Alaska to the desert. I live in Indiana and if it is -0 out my trucks don't crack the thermostat till I get to town 7 mi away. They don't heat the trans and really don't need to unless you can get a trans that the converter locks up in every gear. The only thing a radiator cooler is , is simple non finned tube made out of the same material your lines are that feed and return.
I run a street/strip th350 from TCI in my '55 and had I known that it did not have "kickdown" in it I would have opted for something else. So if I space and don,t down shift my converter is generating a lot of heat. On that one I run a 24 oz aluminum cooler out front. So with that said I believe the rad cooler is the absolute minimum they could get away with.

[ShredSled]

I'd keep it running through the radiator to the remote cooler. I've done it this way on several vehicles and not a problem with one related to that set-up.

[junkyardjohn]

QUIT GUESSING & GOING BY OTHER PEOPLES OPINIONS & PUT A TRANS. TEMP GAUGE IN YOUR TRUCK. HEAT IS THE SINGLE MOST CAUSE OF TRANSMISSION FAILURE. SHOOT... THE GENERAL DIDN'T EVEN PUT DUMMY LIGHTS IN FOR THE TRANNY. JOHN

[mrein3]

I've posted this before...
In desert climates, you run the hot fluid to the radiator then the external cooler then back to the transmission.
Up here in MN you run the hot fluid to the external cooler then the radiator then the transmission. You don't want your fluid cooled down too far in the winter. Running it through the warm radiator keeps it from returning to the transmission too cold.

[mrein3]

Oh and I do run a heat gauge. For giggles I made a run pulling my boat BEFORE I installed an external cooler. In stop and go traffic in a town I got up to 240 degrees on the gauge. The next week, same trip, same sets of stop lights, same outside temps I ran 215 degrees with the added cooler.

[ShredSled]

Originally Posted by mrein3

I've posted this before...
In desert climates, you run the hot fluid to the radiator then the external cooler then back to the transmission.
Up here in MN you run the hot fluid to the external cooler then the radiator then the transmission. You don't want your fluid cooled down too far in the winter. Running it through the warm radiator keeps it from returning to the transmission too cold.

Since I live in MI where it gets cold, I always run a bypass valve (forgot what it's called, but made by Long and optional with Tru-cool coolers) before my external cooler that way my trans fluid can get up to operating temps quicker. Then once temps are up, the valve opens and lets fluid flow through the cooler.

I too also run a trans temp guage. Mine has never exceeded 200 since installing the cooler and bypass valve, and it's run through the radiator too.

[Sub-versive]

My '77 3/4T Burb the lines from the TH400 run to the rad, then to another trans cooler. Never a problem. This set-up worked in AZ when the sub was my uncles, and he pulled a 32' Airstream all the time. He lived there for 12-15 years too.

[lyrikz]

Originally Posted by junkyardjohn

QUIT GUESSING & GOING BY OTHER PEOPLES OPINIONS & PUT A TRANS. TEMP GAUGE IN YOUR TRUCK. HEAT IS THE SINGLE MOST CAUSE OF TRANSMISSION FAILURE. SHOOT... THE GENERAL DIDN'T EVEN PUT DUMMY LIGHTS IN FOR THE TRANNY. JOHN

Trans temp guage huh? Sweet, another reason to buy stuff. ahah. I will get one.. What is the optimal temperature to run, and at what temp would i want to shut the rig off becuase something was wrong?

Originally Posted by mrein3

Oh and I do run a heat gauge. For giggles I made a run pulling my boat BEFORE I installed an external cooler. In stop and go traffic in a town I got up to 240 degrees on the gauge. The next week, same trip, same sets of stop lights, same outside temps I ran 215 degrees with the added cooler.

Thats some cool info.. They help alot then it seems.

Originally Posted by Sub-versive

My '77 3/4T Burb the lines from the TH400 run to the rad, then to another trans cooler. Never a problem. This set-up worked in AZ when the sub was my uncles, and he pulled a 32' Airstream all the time. He lived there for 12-15 years too.

Nice, im leaving my setup alone and picking up a temp guage.

[big_al_71]

I live in South Florida and it is super hot during the summer months I ran my tranny lines to the cooler and back to the tranny not thru the radiator at all.

[mrein3]

Originally Posted by lyrikz

Trans temp guage huh? Sweet, another reason to buy stuff. ahah. I will get one.. What is the optimal temperature to run, and at what temp would i want to shut the rig off becuase something was wrong?

I know a guy that won't move his truck until his tranny temp gets to 100 F.
I'm not sure what the high end is but when my gauge hit 240 pulling my boat that day I was starting to think of contingency plans. As soon as I got out of that town things cooled off some.

I'm thinking you want 100 - 200 degrees Fahrenheit. The trouble with shutting it down at say 250 degrees, is that all that hot fluid is stuck in the transmission and not moving around any more.

FWIW, I have my gauge mounted knee-knocker style under my ignition.

[junkyardjohn]

I LIKE THE AUTO-METER GAGES (AROUND $50) BUT ANY EL-CHEAPO BRAND IS ABOUT A MILLION TIMES BETTER THAN NONE. 99% OF TRANSMISSIONS ARE OVERHEATED & DESTROYED WITHOUT THE OWNER EVER KNOWING WHAT WENT WRONG. THEY'RE AWFULLY CHEAP INSURANCE. JOHN

[Fitz]

Originally Posted by big_al_71

I live in South Florida and it is super hot during the summer months ....

Everything is relative and South florida ain't hot....not compared to the Sonoran Desert it ain't. There's a lot of folklore in this thread so I ran a little experiment this AM on the way into the office. It's Friday and for a treat i drove my truck! Before the engine size argument comes up you should know I'm rinning a 67 stepside with a ZZ572 powerplant tied to a JW Performance built Turbo 400. It takes a big Rad to keep that beast cool. My truck has coolers and temp guages for trans fluid and engine oil as well as the normal engine coolant temp.

First off, the temp of the water in your radiator does not affect the trans oil temp in a radiator with a built in trans cooler. Not at all. The Trans cooler built into your radiator is cooled by the same mechanism as the engine coolant. It is a two fluid heat transfer path; fluid in the tube through the fins to ambient air. AIR is the second fluid not the water on the engine side. The temperature differential between the air and fluid in the tube sets the heat transfer rate through the thermal resistance of the fins. That is why after running 30 miles at 75 MPH on I-10 this morning my engine coolant is steady at 195 degrees, engine oil is rock solid at 220 degrees and the trans fluid temp was steady at...144 degrees. That's 56 degrees cooler than the engine coolant in a BeCool 4 row Rad with built in trans cooler only (no external trans cooler). What keeps the trans fluid temps down is the radiating SURFACE AREA of the FINS connected to the tubes carrying the trans fluid. My rad is 16 in high and the four vertical tubes carrying the trans oil are spaced 1.5 inches apart and 1/2 in behind the tubes carrying engine coolant. That's 0.75 sq in / fin and there are 108 sq inches in the cooling area of the rad with 10 fins per inch for the trans giving 1080 square inches of radiating surface for my trans cooler. That's why my trans temp is steady and 56 degrees cooler than the engine coolant. If you want to make comparisons between coolers you need to determine the surface area of each fin and multiply that by the number of fins.

You will find that the frame mounted trans coolers can help keep you out of trouble but will never be as effective as a cooler mounted in front of your Rad or one built into your rad...size matters but not the size you think...it's the area of the radiating surface that matters and that's the total area of the fins not the length times height of the cooler you're running.

When it's 115 here in the summer (and yes, Big Al we average 87 days a year above 105 degrees so it's more than a little bit hotter here in the Arizona Desert than South Florida...no ocean here to moderate the temps!) my trans runs cool!

[Fitz]

Originally Posted by big_al_71

I live in South Florida and it is super hot during the summer months ....

Everything is relative and South florida ain't hot....not compared to the Sonoran Desert it ain't. There's a lot of folklore in this thread so I ran a little experiment this AM on the way into the office. Before the engine size argument comes up you should know I'm running a 67 stepside with a ZZ572 powerplant tied to a JW Performance built Turbo 400. It takes a big Rad to keep that beast cool. My truck has coolers and temp guages for trans fluid and engine oil as well as the normal engine coolant temp.

First off, the temp of the water in your radiator does not affect the trans oil temp in a radiator with a built in trans cooler. Not at all. The Trans cooler built into your radiator is cooled by the same mechanism as the engine coolant. It is a two fluid heat transfer path; fluid in the tube through the fins to ambient air. AIR is the second fluid not the water on the engine side. The temperature differential between the air and fluid in the tube sets the heat transfer rate through the thermal resistance of the fins. That is why after running 30 miles at 75 MPH on I-10 this morning my engine coolant is steady at 195 degrees, engine oil is rock solid at 220 degrees and the trans fluid temp was steady at...144 degrees. That's 56 degrees cooler than the engine coolant in a BeCool 4 row Rad with built in trans cooler only (no external trans cooler) and it stayed that way for half an hour. What keeps the trans fluid temps down is the radiating SURFACE AREA of the FINS connected to the tubes carrying the trans fluid. My rad is 16 in high and the four vertical tubes carrying the trans oil are spaced 1.5 inches apart and 1/2 in behind the tubes carrying engine coolant. That's 0.75 sq in / fin and there are 108 sq inches in the cooling area of the rad with 10 fins per inch for the trans giving 1080 square inches of radiating surface for my trans cooler. That's why my trans temp is steady and 56 degrees cooler than the engine coolant. If you want to make comparisons between coolers you need to determine the surface area of each fin and multiply that by the number of fins.

You will find that the frame mounted trans coolers can help keep you out of trouble but will never be as effective as a cooler mounted in front of your Rad or one built into your rad...size matters but not the size you think...it's the area of the radiating surface that matters and that's the total area of the fins not the length times height of the cooler you're running.

When it's 115 here in the summer (and yes, Big Al we average 87 days a year above 105 degrees so it's more than a little bit hotter here in the Arizona Desert than South Florida...no ocean here to moderate the temps!) my trans runs cool!