4R70W suddenly overheating

[rocknhorse76]

While driving in the wet snow yesterday, my 4R suddenly started overheating. It was shifting normally for the most part and not making any weird noises (other than a slight hiccup while cruising at about 50 mph on the pavement that I’m pretty sure is due to a loose pin on my QUICK 4 controller). Fluid level was good but the coolers were both cold to the touch, so no fluid was flowing through them. This transmission has never overheated before, so I’m not sure what happened. Going to pull lines off to check for flow (they were cold too) then drop the pan tonight and cross my fingers that maybe the filter came loose. FYI I don’t run a thermo bypass, so it’s definitely not that. Anybody ever have similar issues?

 

[nvrstuk]

Your new moniker is Bad Luck Tim.

Meet ya for lunch this week and figure it out!

 

[rocknhorse76]

Dude you’re not kidding. If it wasn’t for bad luck I’d have none at all!

 

[Broncobowsher]

Check that you didn't crush, pinch, kink a line. That will stop fluid flow.

 

[rocknhorse76]

Check that you didn't crush, pinch, kink a line. That will stop fluid flow.

Checked them yesterday. All good.

 

[nvrstuk]

The odd thing that's happening that we talked about last night about this is that you're not getting fluid through your cooler, BUT the transmission is shifting and driving fine-just getting hot.

Maybe pull both lines to your cooler, connect an air hose (throttle down to 10psi) and blow thru the hose & filter and see if you can blow fluid all over your shop! lol

Actually, I think it's a good idea to be able to 100% eliminate your cooler. And you're lying and then you can drop the pan.

Obviously, unless the 4r is really different internally is that if your pump isn't getting fluid to it, like if the filter fell off- then you wouldn't be getting enough fluid anywhere in the transmission (I think), not just through your cooler, but maybe that cooler line or a cooler port is after where the fluid goes into the parts of rhe valve body & solonoids that allow the transmission to work. I have no idea. I'd have to pull it apart or look in a manual and follow fluid flow charts.
Clueless here.

I'm calling ya‐ easier!

 

[66broncoCT]

How do you know it was overheating? Maybe your gauge or temp sensor or whatever you were using to tell it was overheating is just giving a false reading?

 

[rocknhorse76]

How do you know it was overheating? Maybe your gauge or temp sensor or whatever you were using to tell it was overheating is just giving a false reading?

Both temp sensors (internal to the trans with display on my trans controller and my aftermarket gauge with sensor in the pressure test port) said it was hot. Hot vapors, not quite smoke coming out of the vent hose I have routed up to the engine compartment. Snow sizzling when I threw it on the trans case. Yeah pretty sure that all indicates that it’s hot lol.

 

[rocknhorse76]

The odd thing that's happening that we talked about last night about this is that you're not getting fluid through your cooler, BUT the transmission is shifting and driving fine-just getting hot.

Maybe pull both lines to your cooler, connect an air hose (throttle down to 10psi) and blow thru the hose & filter and see if you can blow fluid all over your shop! lol

Actually, I think it's a good idea to be able to 100% eliminate your cooler. And you're lying and then you can drop the pan.

Obviously, unless the 4r is really different internally is that if your pump isn't getting fluid to it, like if the filter fell off- then you wouldn't be getting enough fluid anywhere in the transmission (I think), not just through your cooler, but maybe that cooler line or a cooler port is after where the fluid goes into the parts of rhe valve body & solonoids that allow the transmission to work. I have no idea. I'd have to pull it apart or look in a manual and follow fluid flow charts.
Clueless here.

I'm calling ya‐ easier!

Yeah it was definitely easier to talk on the phone haha

 

[66broncoCT]

Both temp sensors (internal to the trans with display on my trans controller and my aftermarket gauge with sensor in the pressure test port) said it was hot. Hot vapors, not quite smoke coming out of the vent hose I have routed up to the engine compartment. Snow sizzling when I threw it on the trans case. Yeah pretty sure that all indicates that it’s hot lol.

Yep sure sounds like it was hot haha. Just figured I’d throw out the easy solution before you tore into it. I’m no transmission wizard but if it was shifting fine and the coolers were cold I’d think it has to be a plug somewhere within the cooling circuit because you clearly still had fluid flow/pressure within the transmission. Either plugged in the lines or possibly internally in the transmission

 

[rocknhorse76]

Yep sure sounds like it was hot haha. Just figured I’d throw out the easy solution before you tore into it. I’m no transmission wizard but if it was shifting fine and the coolers were cold I’d think it has to be a plug somewhere within the cooling circuit because you clearly still had fluid flow/pressure within the transmission. Either plugged in the lines or possibly internally in the transmission

Haha all good man. I appreciate the response. I plugged my laptop in to the controller tonight to check line pressure and temps. Line pressure is exactly where my tune says it should be and it shifts perfectly. TC even locks when it should. Just absolutely no flow to the coolers. I’ll disconnect the lines and blow them out tomorrow night. Meanwhile, I’m checking out diagrams on flow through the trans.