The Swamp Fox
New Member
- Joined
- December 7, 2019
- Messages
- 4
- Reaction score
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- Year, Model & Trim Level
- 2006 Ford Explorer XLT
Hello all,
I'm new to both my Ford Explorer and the forums here. I am currently having some transmission trouble, and am hoping to learn from those who have found themselves in my situation before. The vehicle in question is a 2006 Ford Explorer XLT with the 4.0L V6 engine and 5R55S 5-speed automatic transmission.
The engine is running flawlessly and the vehicle is in great shape for the year. I'm trying to ascertain whether the transmission issue is serious enough that it will require a rebuild / replacement, or whether the slipping is caused by a more peripheral issue such as a bad sensor that would be a far less expensive repair.
I'm no rookie under the hood, but have (fortunately) never had transmission issues before and know next to nothing about them. That said, I am eager to learn.
History of Transmission Performance
For several years now, the transmission has slipped slightly in reverse when under a heavy load, such as when backing up a steep incline or when backing up with a loaded trailer. The slipping was usually preceded by a significant mechanical shuddering. However, the Explorer would walk up a hill in reverse no problem when in 4x4 Low. No other slipping or shifting issues ever presented.
Some time ago, the driver side transmission oil cooler fitting at the radiator sprung a slow ATF leak. I successfully fixed this by replacing the two O-rings contained within the fitting. I then carefully followed the Ford Service Manual procedure for topping off the automatic transmission fluid:
A few weeks later, the slipping in reverse worsened. The only thing I can figure is that the 3 quarts of new fluid may have been enough to have the effect of eating away any built-up grime on the clutch plates, contributing to additional slip. This seems plausible given that I don't even know the last time the transmission fluid was flushed or the pan dropped.
Possible Causes
Given the fact that topping off the fluid didn't resolve the slipping in reverse, my first thought as to cause would be a worn reverse band. But if I'm dealing with a worn band, I'm confused as to why Reverse worked flawlessly in 4x4 Low for years under heavy load with no issues. The only theory I've read that could possibly explain this is that the lower gearing of 4x4 Low lowers the torque requirements on the transmission. Does this seem like a valid explanation?
Note that I never experienced an instant loss of Reverse or a loud "bang" that others describe when the band ears break off. One alternative explanation to a worn or broken band that would possibly explain why Reverse worked so well for years in 4x4 Low and not in 2WD is worn gears in the transfer case.
Another possible cause seems to be a broken sprag one-way clutch. Does this seem likely?
Last but not least, the symptoms described here on the forums in a related thread exactly match those of my Explorer. The problem in that case turned out to be the Manual Lever Position Sensor (MLPS) which was failing to properly boost the line pressure in reverse.
Summary
The transmission shifts beautifully under normal 2WD driving, including hard acceleration and heavy load (trailering). The only problem is Reverse.
The only Check Engine Light which is relevant is P0720 — Output Speed Sensor Insufficient Input. It sounds like this error can be triggered when the PCM detects an out-of-range relationship between engine RPM and transmission output rotational speed.
I'm trying to nail down whether I'm looking a worn clutches / bands requiring expensive repairs, or whether it's possible this issue is related to the transfer case or simply a bad sensor like the MLPS which may be a much simpler and less expensive repair. Any and all input as to underlying cause or further tests which I can perform to narrow the list of possible causes would be appreciated.
I'm new to both my Ford Explorer and the forums here. I am currently having some transmission trouble, and am hoping to learn from those who have found themselves in my situation before. The vehicle in question is a 2006 Ford Explorer XLT with the 4.0L V6 engine and 5R55S 5-speed automatic transmission.
The engine is running flawlessly and the vehicle is in great shape for the year. I'm trying to ascertain whether the transmission issue is serious enough that it will require a rebuild / replacement, or whether the slipping is caused by a more peripheral issue such as a bad sensor that would be a far less expensive repair.
I'm no rookie under the hood, but have (fortunately) never had transmission issues before and know next to nothing about them. That said, I am eager to learn.
History of Transmission Performance
For several years now, the transmission has slipped slightly in reverse when under a heavy load, such as when backing up a steep incline or when backing up with a loaded trailer. The slipping was usually preceded by a significant mechanical shuddering. However, the Explorer would walk up a hill in reverse no problem when in 4x4 Low. No other slipping or shifting issues ever presented.
Some time ago, the driver side transmission oil cooler fitting at the radiator sprung a slow ATF leak. I successfully fixed this by replacing the two O-rings contained within the fitting. I then carefully followed the Ford Service Manual procedure for topping off the automatic transmission fluid:
- Warm up transmission to 80-120° F.
- Park on a level surface (verified via level on running board)
- With engine running and transmission in Park, loosen drain plug
- Pump Mercon V ATF into transmission until it begins draining out
- Re-seal drain plug when transmission is no longer draining a steady stream of ATF
A few weeks later, the slipping in reverse worsened. The only thing I can figure is that the 3 quarts of new fluid may have been enough to have the effect of eating away any built-up grime on the clutch plates, contributing to additional slip. This seems plausible given that I don't even know the last time the transmission fluid was flushed or the pan dropped.
Possible Causes
Given the fact that topping off the fluid didn't resolve the slipping in reverse, my first thought as to cause would be a worn reverse band. But if I'm dealing with a worn band, I'm confused as to why Reverse worked flawlessly in 4x4 Low for years under heavy load with no issues. The only theory I've read that could possibly explain this is that the lower gearing of 4x4 Low lowers the torque requirements on the transmission. Does this seem like a valid explanation?
Note that I never experienced an instant loss of Reverse or a loud "bang" that others describe when the band ears break off. One alternative explanation to a worn or broken band that would possibly explain why Reverse worked so well for years in 4x4 Low and not in 2WD is worn gears in the transfer case.
Another possible cause seems to be a broken sprag one-way clutch. Does this seem likely?
Last but not least, the symptoms described here on the forums in a related thread exactly match those of my Explorer. The problem in that case turned out to be the Manual Lever Position Sensor (MLPS) which was failing to properly boost the line pressure in reverse.
Summary
The transmission shifts beautifully under normal 2WD driving, including hard acceleration and heavy load (trailering). The only problem is Reverse.
The only Check Engine Light which is relevant is P0720 — Output Speed Sensor Insufficient Input. It sounds like this error can be triggered when the PCM detects an out-of-range relationship between engine RPM and transmission output rotational speed.
I'm trying to nail down whether I'm looking a worn clutches / bands requiring expensive repairs, or whether it's possible this issue is related to the transfer case or simply a bad sensor like the MLPS which may be a much simpler and less expensive repair. Any and all input as to underlying cause or further tests which I can perform to narrow the list of possible causes would be appreciated.