In need of some help diagnosing this issue. A few days ago I was out driving and stopped for gas, was in quite of a hurry due to weather so I was hard on the acceleration. Noticed some clunking going on when the trans was shifting into 2nd as I was leaving. It only did this a few times and never did it again. My O/D Off light was flashing so I pulled over and shut the truck off. A tornado warning was just issued for our area so checking for a code wasn't on my mind at the time lol. Restarted the truck and all was fine, hasn't done it since. I have a 5r55e trans, is this a valve body or solenoid issue or am I looking at a new trans?

 

5R55E uses OD for 2nd gear, its a combo gear, 1st + OD on = 2nd
This gives a smoother shift when slowly accelerating
The computer has the option to skip 2nd and go directly to 3rd from 1st, if driver is "hard on the acceleration"
So it holds 1st longer to get RPMs higher then shifts to 3rd

But OD light flashing shouldn't happen if that was all that was going on
Flashing OD light will mean a transmission code was set and will be in memory, so I think getting that code or codes, would be first thing to do
These Transmission codes are all P07xx and not all code readers can see or get them, auto parts store may have one and they will read codes for free
Transmission shop will be able to read them for sure but sometimes charge to do that

So I would get the code and go from there


History of 5R55E
A4LD was first light truck 4-speed OD trans, used in 1985, 1 solenoid at first then 2 solenoid Valve Body, 1st solenoid locked torque converter and 2nd solenoid was OD on/off, which is important
Off-roaders found that they could use the OD on/off solenoid to "split gear ratios", i.e. in 1st you could manually activate OD and get a split ratio between 1st and 2nd, and same for between 2nd and 3rd, so the 4-speed was now a 6-speed, or 6 ratio gear box, which is handy in 4low as well as 2WD or 4H, to find just the right RPM for speed gear ratio

In 1995 A4LD got a 6 solenoid valve body, and was renamed 4R55E, still a 4-speed, but computer now had full shift control
In 1998 Ford engineers added software to the computer to automatically turn on OD when shifting from 1st to the old 2nd, making a faux 2nd gear, so it was renamed again to the 5R55E 5-speed, and it is a 5-speed, just a clever way to add a gear ratio, and all thanks to the 4x4ers, but I am sure Ford thought of it on their own.....................

 

Tried getting a code via the Torque app and then a professional scan tool, neither turned up any codes.