You're overthinking it.

When everything is working correctly fluid flows to the coolers without the bypass doing anything. The spring holds the ball on the seat. If pressure builds too high it overcomes the spring and pushes the ball off of the seat. Now fluid flows through the bypass instead of to the coolers.

 

thanks!!, just for my own understanding, what is the purpose of the valve in the banjo bolt?

 

hey, i have one last question , i got sidetracked changing out ujoints and cardan, but on the bd bypass delete, they came with a spacer and metal washers on either side, i rebuilt the bypass valve (literally 5 minutes, very simple), should i replace the metal washers with a hard plastic or hard rubber pieces ( i discarded the the original ones), there seems to be the smallest amount of fluid at the joint currently with the delete package...

also when i unhook the tranny lines to put the bypass back in, how much fluid should i expect to drain out?

 

I have an 03 F250 that I’ve had some transmission problems with for a while now and no one can seem to determine why. I only have issues when I’m traveling on the interstate for an hour or more and speeds of 70 or better. The transmission will get hot, but when I pull off, it will cool down as the truck downshifts. After 10 minutes, I can jump back on and it will be fine for another hour or so before it gets hot again. I’ve had a new cooler installed along with some other work that folks have recommended, but it still gets hot under those specific conditions. I’m reading in here that it could be the transmission oil cooler bypass valve. Does anyone else have any advice?

 

You could should run a cooler flow test, assuming you have a 4R100 transmission, I can't tell from your description.

1. Get two containers, each at least a gallon. Get a friend to help.

2. Warm up the trans.

3. Remove the cooler line where it attaches to the rear of the trans. Point the line into the first container.

4. Have your friend start the engine, leaving it at idle in park.

5. As soon as the flow is steady (should only be 2-3 seconds) move the line to the second container. NOTE: If there is fluid spraying out of the transmission SHUT THE ENGINE OFF. This indicates the test has failed. A small drip, or even a few drips out of the trans is normal.

6. Keep the line in the second container for EXACTLY 15 seconds, then move it back to the first container and shut the engine off.

7. If there is at least one quart in the second container it passes and the flow is normal. If there is less than a quart, or there was a spray coming from the trans it fails the flow test.

A failed test means one of three things.

a. There is a restriction in the cooler circuit. This could be a damaged/kinked/pinched hose, debris in one or both coolers, or a damaged cooler.

b. The bypass valve on the side of the trans has failed. Rebuild kits are available. They are inexpensive and easy to install.

c. The pump is worn out. This is not very common, but it can happen.

 

I ordered the new cooler bypass valve and it looks pretty easy to install, but I have one question. Can I just remove the old one and replace it with the new one or do I need to drain the transmission first?

 

You don't need to drain the transmission.

 

Get a obd2 dongle and a scanner app. I recommend torque pro. It will show the exact transmission temp.
If all is working as designed (no clogged cooler) these transmissions should not overheat. I've taken the 4r100 in some toasty arizona weather (115f) and it would not overheat.

 

We had it hooked up to a scanner that told us the temp before I replaced the cooler and the new cooler definitely worked. Now it’s only doing it on long runs at high speeds on the interstate. I’m going to replace the cooler bypass Friday and I guess we’ll see what happens from there.

 

Is that solo or with trailer? Solo it should absolutely not overheat at that speed, not even at high ambient temps.
Unless it goes uphill, the converter should be locked and there is no slip , so less heat. At least I think that's how it works with my limited knowledge of these transmissions.

 

No trailer, but it’s lifted with 37” tires.

 

I replaced the cooler bypass valve assembly and now it’s blowing transmission fluid everywhere.

 

Then you didn't install it correctly.

 

You’re right. One of the bolts for cross threaded and I didn’t realize it. Unfortunately steel bold damaging aluminum threads is unforgiving, so we’re back to the drawing board. Everything seemed to go together just fine and I had no idea that they were cross threaded, but a friend who’s a mechanic looked and noticed that the new part was just an 1/8 of an inch too short and told me that I shouldn’t have used a socket wrench to tighten it because I couldn’t feel the threads. Thanks for the advice...I may be in the business for a new transmission now.

 

You can probably repair the thread with a Heli-Coil.