4r75e Overheating

[DIRTRIDER]

Hello everyone! I haven't visited the forum for a long time. I encountered a problem typical for my model. Namely, overheating of the transmission. Having studied almost all the material related to the transmission model, I still couldn’t find the most important thing: I'm looking for a detailed diagram of the coolant line fluid supply. In order not to mislead, I will write down point by point what exactly worries me and what I checked.
1. The oil is new, so is the filter.
2. The transmission does not slip or kick. There is not the slightest hint of a malfunction. All gears shift perfectly!
3. Transmission oil barely flows from the transmission itself. There is not enough pressure even to fill the entire coolant circuit.

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There is no thermostat initially. The cooler lines are brand new and clean, the cooler is new, the oil level is normal. There are no debris in the oil pan. The oil smell and color are excellent. There is just no fluid coming out of the transmission. Help!

I'm looking for a clear diagram that shows the entire path from the beginning of the oil intake to the exit from the transmission. I can't find anything like it.

[boywonder]

How do you know the flow is low?

Have you disconnected a line, started the van and watched it flow into a bucket?

How do you know it overheating? Do you have an OBDII device connected that gives you trans fluid temperature? Is the temp over 200F?

Did you add an aftermarket cooler?

[JWA]

Originally Posted by boywonder

How do you know the flow is low?

Have you disconnected a line, started the van and watched it flow into a bucket?

How do you know it overheating? Do you have an OBDII device connected that gives you trans fluid temperature? Is the temp over 200F?

Did you add an aftermarket cooler?

Great questions, same as I was about to ask!

According to Mark K on FTE fluid flow through the external cooling circuit won't exceed about 15 PSI, very low flow.

Here's a marked-up drawing I did for such questions. The red and blue colors represent relative fluid temperatures once the vehicle is warmed up and running, red = "hot", blue = "cold"

This would be typical of an E-350 2005 w/4R75E (my own) behind a 5.4 gasoline engine.

HTH

[kbeefy]

How hot is hot?


The 4R75E does have a thermo valve in the cooling circuit, if it's not up to temp you won't get much flow to the cooler. Sometimes we would have to 'powerbrake' to keep fluid temps up enough to complete a fluid exchange.

[DIRTRIDER]

Originally Posted by boywonder

How do you know the flow is low?

Have you disconnected a line, started the van and watched it flow into a bucket?

How do you know it overheating? Do you have an OBDII device connected that gives you trans fluid temperature? Is the temp over 200F?

Did you add an aftermarket cooler?

Of course I have a scanner. I even have an analog sensor to compare temperatures. It is located in the test port. The overdrive (shifter indicator) warning light starts flashing at 235 degrees. I took a test. A quart should be filled in 15 seconds. I pick up a quart in 4 minutes. New lines, new radiator, new cooler. Not original.

[DIRTRIDER]

Originally Posted by kbeefy

How hot is hot?


The 4R75E does have a thermo valve in the cooling circuit, if it's not up to temp you won't get much flow to the cooler. Sometimes we would have to 'powerbrake' to keep fluid temps up enough to complete a fluid exchange.

Some versions did not have a thermostat. This is exactly what I own.

[DIRTRIDER]

Originally Posted by JWA

Great questions, same as I was about to ask!

According to Mark K on FTE fluid flow through the external cooling circuit won't exceed about 15 PSI, very low flow.

Here's a marked-up drawing I did for such questions. The red and blue colors represent relative fluid temperatures once the vehicle is warmed up and running, red = "hot", blue = "cold"

This would be typical of an E-350 2005 w/4R75E (my own) behind a 5.4 gasoline engine.

HTH

Thank you. I meant the internal circuit. More complex. How oil is taken inside and released into the lines.

[carringb]

Did you sample from the hot line? To rule out an obstruction in the cooling loop…

There is also a pressure relieve valve in the cooler outlet port, meant to bypass the cooler loop if it’s plugged. If that bypass valve spring beaks or gets plugged with debris, it will bypass full time. I suspect this might be your issue.

[DIRTRIDER]

Originally Posted by carringb

Did you sample from the hot line? To rule out an obstruction in the cooling loop…

There is also a pressure relieve valve in the cooler outlet port, meant to bypass the cooler loop if it’s plugged. If that bypass valve spring beaks or gets plugged with debris, it will bypass full time. I suspect this might be your issue.

well… you mean the transmission outlet port or thermostat port where the spring is usually brakes? I dont have thermostat and never had it before.

[carringb]

Originally Posted by DIRTRIDER

well… you mean the transmission outlet port or thermostat port where the spring is usually brakes? I dont have thermostat and never had it before.

I just double checked and the pressure relief spring is part of the thermal bypass valve on the 4R75. This is located in a square aluminum block external of the transmission, and should be on all 4r75s. It it’s not near the inlet/outlet of the trans, it should be hanging next to the starter. Looking at the valve body diagram, this is the only place I can see fluid bypassing without also causing other major symptoms. https://youtu.be/tDaTL0tVSh8?si=dp7fOuR4yy7-09NX