5r55s Whirring and Limp Mode | Ford Explorer - Ford Ranger Forums - Serious Explorations
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5r55s Whirring and Limp Mode


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April 22, 2021
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Year, Model & Trim Level
2004 XLT 4.0 V6 4x4
Some background - I've had my 2004 Explorer v6 4wd for probably 3 years now, and feels like I've replaced pretty much everything. The transmission went out about a year ago, so I pulled a junkyard tranny and swapped it in, at which point I also put in a reman torque converter and applied the AJIE servo bore fix. I also recently had to replace the wheel speed sensors and the rear diff speed sensor.

Anyways, on to the issue at hand. The junkyard tranny never ran like new exactly, just better than the completely destroyed original one. Even after I just put it in about a year ago I noticed hard shifts and long shifts, but it still moved the vehicle so that was good enough for me. But recently I have some new issue cropping up that occur when I am at speed and then let off the gas to decelerate, specifically:
1) The speedo drops dramatically, not matching the speed
2) I can hear a loud whirring, probably coming from the torque converter or transmission
3) Limp mode

Not necessarily in that order. In fact, I think that the speedo mismatch is triggering the limp mode. I'm not sure where the whirring falls in the sequence. But after the car enters limp mode, the whirring occurs every time I decelerate after that point. I do notice that if I keep my foot on the accelerator during deceleration and use my other foot to slow down using the brake... I can keep the speedo from plummeting and the whirring from happening.

Turning the car off and back on resets limp mode and then everything behaves normally again (until it doesn't).

OK, so onto the diagnostics. I did some research and I started monitoring all the relevant sensor outputs while driving to try and see what is going on, and here is what I learned:
1) I definitely don't have a 2nd or a 5th gear. Explains the hard/long shifts.
2) The rear shaft sensor drives the speedo. I read it somewhere around here, and confirmed by watching sensor plots while driving.
3) Per #2, the measured output shaft speed is dropping dramatically during these decelerations. Plotted against the wheel speed sensors there is no coordination for a brief time, until acceleration is resumed.

So. I don't know if it could be an issue with the output shaft sensor, since it seems to work most of the time and that would just be too easy. Going back to whirring noise, I'm leaning towards the torque converter. If I watch the torque converter sensors (Torque Converter Control - TCC, and Torque Converter Clutch Solenoid - TCCS), the TCC during normal driving is set to either 0 or 14, and the TCCS is always either 0% or 100%. When my issues start cropping up, I notice the TCC is set to 11 and I think the TCCS is usually 100%. I'm pretty sure that 0 means clutch off, because ideal slip is listed as 1023 rpm for that setting. I think 14 means full clutch engagement, because ideal slip there is usually listed as 0. I don't know what 11 means. Is the torque converter slipping when it shouldn't, or not slipping when it should maybe? Is the tranny just hosed, binding up inside and stalling the output shaft somehow during deceleration? Any ideas?

Tried uploading a fancy graph, maybe it'll give you an idea.