I thought about deleting the check valve, but transmission repairman talked me into keeping it, so what I actually did is replace it. Tran man works for a private company on fleet of trucks and knew he would never work on my truck. That little hose cost me $45.00.

 

Well, I have never been so happy to hear I screwed up some basic maintenance. I was afraid that I was going to have to pay for a rebuild. I realize that I still might have burnt it up, but hopefully not.
I checked the level again last night, with the truck warm and the transmission *IN NEUTRAL*, and of course it is too full. Not much (anymore), but still overfilled.
I like the concept of the extra filter in the engine compartment anyway, a little more fluid capacity, more filtration, and the metal filter acting as a little heat sink, so I will do that this weekend and see if the transmission acts right afterward.
I still don't understand how I made a 1,000 trip running 80 on the interstates with no problems, then my 40 mile trip home at 70-75 with too much fluid caused this. Maybe the extra fluid caused the check valve to fail after awhile? Maybe slowing down to 75 decreased the cooling enough? Maybe faster is better for it
Thanks again for everyone's time and input.

 

Okay, I removed the line with the check valve and installed a remote oil filter in it's place. I just took a 20 mile drive to town and back, and didn't have any trouble. O/D seemed to run fine, and I didn't have the trans temp light come on again. This was a back road trip with a top speed of 55, but I'm confident enough to get back on I-840 again tomorrow. I didn't drop the pan again, but I will keep checking for drips or leaks. Thanks again for everyone's input. Here's the new filter:

 

Hope it works out for you, that external filter does seem like a good idea. Not sure about not having a check valve, something is going to drain (I think torque converter). It does sound like your check valve was plugged.

 

I Made Sure That I Picked A Filter With An Anti-DrainBack Valve, SO I Still Have The Check Valve, In A Way.
Sorry About The Weird Caps, Jellybean Is Acting Weird.

 

I don't know the guy you talked to, but most good tranny shops will not warranty the tranny unless that check valve is removed.

 

Okay, I made the 40 mile trip to work this morning, and the return trip home without losing overdrive again, but I am running too many rpms. At 70 on I-840, I had been at 1800-2000 rpms. Today, I was running 2200-2400, and it didn't seem like overdrive was locked in properly. It felt like the clutch was slipping if I had to give it a little more throttle to get up a hill. It felt the same between 50-60 off the interstate.
I checked the transmission fluid again when I got home, in neutral, and it was good. I didn't see any sign of leaks anywhere, and I don't know what else to check.
What do you guys think?

 

For my 5.9 that would be too many RPM for 70 in OD. Not sure what 70 would be if it didn't shift into OD? Are you sure you see it shift 3 times, the tach is a good indicator, better than just feeling the shift. A little under 2,00 RPM sounds right.

 

What size tires are you running? Mine is at 2100 rpm in OD at what reads 70, but according to two different state troopers, I am running 77 mph. (oversize tires). Speedo will be off, but rpm is not.

 

You could have a couple of things going on, Maybe a bad TPS sensor or brake switch causing the transmission not to go into lock up. Or even could be a bad output speed sensor. The best way to find out whats going on, is to hook up a 300 psi pressure gauge to each port and post your readings. By any chance did you adjust both kick down bands and adjust the throttle pressure cable. AKA (TV) cable. Also do you know what the flow rate that coming from the front pump?