I was told long ago if you ever feel you know everything about transmissions, it’s time to find a new career. I didn’t fully understand what my friend Mac told me then, but I think I got his point over the years. We’ll never stop learning something new as long as we keep turning wrenches with an open mind.
I recently had a 2014 Ford F150 with a 6R80 come in with no fourth, fifth, or sixth, and a P0771, shift solenoid E performance, stuck off. The shops I build for try their best to save their customers money and only fix what needs to be fixed. We don’t want to rebuild a transmission when a solenoid can fix the problem. The possible causes for this code can be a command to the solenoid, the solenoid valve being stuck, a leak in the hydraulic circuit, or an internal mechanical failure. This is a non-electrical code, which means the circuit is complete but does not mean the computer is operating the solenoid as it should.
Our standard procedure to diagnose this code is to first verify the customer complaint. The F150 neutralized on the three-four shift on the road test. We put it on the lift and had the same issue. Usually, a hydraulic leak (even with burnt clutches) will shift through the gears on the lift with no load on it. This one did not. Next, we put an amp clamp on the wire for solenoid E (figure 1) to verify the computer was actually commanding it. A question often asked here is what should the amperage be? Most manufacturers don’t give this type of information, so I have always checked other similar solenoid wires that are operating normally to see what it should be and compare. Fortunately, in this case, the information is available. These solenoids operate at 850 ma on and 50 ma off. This one appeared to be commanding the solenoid as it should.
So, the list of possible causes was narrowing. If the clutches were burnt to the point they wouldn’t pull on the lift, we should find them in the pan. The pan was spotless. So now we had either a solenoid, valve, major leak in the circuit, or a hard parts failure. Our next step was to drop the valve body and air-check the E clutch (figure 2), which air-checked perfectly. 
We should have heard a major leak if the drum was cracked, the bushings were worn, or the seals were damaged. Now our list was down to a mechanically faulty solenoid, a stuck valve, or hard part damage. I opened the valve body to find the E clutch valves were free (figure 3), and to this point, I have not seen any hard part failures on this, so I condemned the solenoid (figure 4). I would want to test the solenoid, but like most, I do not have the means to flow test these solenoids. We could not get the solenoids separately, and I didn’t have any old valve bodies to take a solenoid off to use, so we got a valve body, installed it, and it was out the door.
So far, this process has worked for us many times without issue until a 2015 Ford Transit showed up and ruined our day. As we all know, even getting the pan off is a nightmare since the frame has to come down. And then add to the problem of rusted frame bolts. We did the normal routine, and everything was the same as the F150. It air checked well, and the pan was clean. We installed a valve body, but this one didn’t go away. We had the same problem on the test drive, so we apparently had a hard part failure. And, of course, it wouldn’t happen with an easy one to pull. My ears were burning that day.
We were confident some splines were stripped at this point, so we removed the trans and got it to my shop. I wanted to figure out a way to prevent this from happening again and what we had to change in our diagnosis routine. Before disassembly, I tried applying air to the A and E clutches while turning the output shaft. I not only felt the grinding in the output shaft but heard it. I found the rear planet splines were stripped where the 4-5-6 hub engaged (figure 5). After we got the new planets and installed them, I did this test again. With both clutches applied, there was a significant difference in the amount of effort required to turn the output shaft since we were also turning the drive train with it.
Hopefully, with this new step added to our routine, we will prevent this problem from occurring again. As we go through the life of a transmission rebuilder, we will make mistakes. If we learn from them, we can prevent future transmissions from landing back on the bench.
