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2006 Ford Explorer XLT w/5R55S Automatic Transmission Slipping In Reverse

Discussion in 'Stock 2006 -2010 Explorers' started by The Swamp Fox, December 7, 2019.

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  1. The Swamp Fox

    The Swamp Fox New Member

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    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 SOHC engine, 5R55S 5-speed automatic transmission, 4x4, and the 3:73 rear axle with tow package. The vehicle has approximately 310,000 miles on it and is still on the original engine and transmission as far as I know.

    On account of both the mileage and the fact that this vehicle was recently given to me, it owes me nothing. That said, the engine is running flawlessly and the vehicle is in great shape for the year and mileage. 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. The underlying cause will likely determine what I do with the vehicle, as I am reticent to put $1,000+ into repairs given the mileage.

    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
    Context behind us, on to the issue at hand. The Explorer previously belonged to my Dad, so I am somewhat familiar with its history. He purchased it in 2015 with 240,000 miles on the clock. For several years now the transmission has slipped 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.

    About six months ago, the driver side transmission oil cooler fitting at the radiator sprung a slow ATF leak. Given Ford's frustrating design decision to roll with a sealed transmission, topping off the fluid wasn't as easy as pulling a dipstick, so my Dad did nothing about it given the fact that the leak was quite slow and the transmission continued to shift normally (aside from the occasional slip in reverse when trailering). When the vehicle was given to me, I investigated the leak at the radiator and successfully fixed it 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:
    1. Warm up transmission to 80-120° F.
    2. Park on a level surface (verified via level on running board)
    3. With engine running and transmission in Park, loosen drain plug
    4. Pump Mercon V ATF into transmission until it begins draining out
    5. Re-seal drain plug when transmission is no longer draining a steady stream of ATF
    The Explorer took almost exactly 3 quarts of Mercon V ATF to become full. I was hopeful that these three quarts would eliminate or reduce the slipping problem in reverse when under load, but it didn't appear to make a difference one way or the other. Fast forward about two weeks and under 100 miles later, and we had an unseasonably early 6-8" of heavy, wet Michigan snow. After wrapping up some deer hunting, I nearly got stuck attempting to back out of a two-track when in 4x4 Low. I thought the tires were simply spinning, but found upon arriving back at "deer camp" and enlisting a spotter that the tires weren't spinning, the transmission was slipping.

    Additional testing revealed that the slipping in reverse is now far worse than it ever was before. The Explorer will only back up in 2WD reverse when on a dead flat, and even then only at idle — any throttle at all and it will slip. And it will no longer back up a moderate incline, even in 4x4 Low and without a trailer. This new development was quite puzzling to me. 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.

    Road Test Results

    I put the vehicle through an extensive road test yesterday to determine the current state of the transmission. Results below:

    2WD
    • Reverse — Slips really bad. Will only back up if on a dead flat and with no throttle. The lightest throttle or incline will cause it to slip.

    • 1st Gear — Tons of available power/torque available when accelerating from a standstill, with no slipping whatsoever encountered. Could probably peel out if I wanted to. Took up to 3,000 RPM and 20 MPH, let off the gas and the RPM's dropped to idle with no engine braking. When I then hit the gas, RPM's came up all the way from idle to 2,200 RPM until the transmission responded, indicating a slip.

    • 2nd Gear — Same results as those above; no slipping when accelerating from a stop, but no engine braking when coasting and slipping upon acceleration out of the coast.

    • 3rd Gear — No problems during acceleration, there is noticeable engine braking, and no slipping when accelerating upon coasting.

    • Drive — Lots of power/torque available when accelerating from a stop and all throughout the range, with no slipping. Plenty of engine braking, and no delays or slipping when punching the gas after coasting at any speed.
    4x4 Low
    • Reverse — Slips really bad but not quite as bad as in 2WD. Can back up much better on a flat and can make it up some slight inclines in reverse.

    • 1st Gear — Instant slipping when accelerating from a stop, no engine braking when coasting, major slipping when accelerating out of the coast.

    • 2nd Gear — Same results as 2WD test.

    • 3rd Gear — Same results as 2WD test.

    • Drive — Instant slipping when accelerating from a stop, slipping even under acceleration in 2nd Gear.
    4x4 High
    • Reverse — Slips really bad but not quite as bad as in 2WD. Can back up much better on a flat and can make it up some slight inclines in reverse.

    • 1st Gear — Same results as 2WD test.
    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. The lack of engine braking when in 1st Gear would seem to corroborate this, as I've read that Reverse and 1st share the same band.

    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 is 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. Given the driving test results for 1st Gear and Drive, 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. Until recently, 4x4 Low would walk a heavy load backwards up a hill all day, but now that's acting up as well. Strangely, multiple gears in 4x4 Low are giving me trouble when those same gears in 2WD are just fine.

    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. My findings will likely dictate the future of the vehicle and whether I take a crack at fixin' er up or wash my hands of her. 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.
     
    Last edited: December 7, 2019
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  3. MotorCityFats13

    MotorCityFats13 Well-Known Member

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    I had a 5r55 in my 2nd gen that broke the ear off of the reverse band and lost reverse and because this band is in the tail of the trans just to replace the band the whole thing needs to be torn down making it pretty normal to do a full rebuild you could look into a band adjustment or if the solenoid is bad but with how reverse is not an often abused gear i would rule out clutch pack wear or solenoid bore wear
     
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  4. boominXplorer

    boominXplorer Elite Ranger Elite Explorer

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    ^^^^ Broken reverse band
     
  5. The Swamp Fox

    The Swamp Fox New Member

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    Thanks a ton for weighing in. What you're saying corroborates much of what I've read regarding the location of the reverse band basically requiring a full rebuild if that is the problem. And I appreciate the thoughts regarding clutch pack and solenoid bore wear being unlikely culprits.

    One additional behavioral aspect that might be relevant is that my Dad had/has a nasty habit of shifting back into Drive while his momentum is still carrying him backwards in Reverse. Would that possibly contribute to any specific one of the possible causes I'm considering?

    What were the symptoms on your 2nd Gen that broke the ear off of the reverse band? Did you lose reverse entirely, or just encounter a lot of slippage in reverse? And did your problems in reverse develop slowly over time, or happen all at once overnight?
     
  6. The Swamp Fox

    The Swamp Fox New Member

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    Well, the consensus thus far regarding a broken band isn't great news... :(

    Would a broken band only cause slipping, or would it completely kill a given gear? And how does the 4x4 Low experience of eliminating the slip (for years, at least) play into the equation if the gear has been broken for some time? As mentioned, I know very little about transmissions, but am trying to understand cause-and-effect logic since the stakes in this case are rather high for me.
     
  7. boominXplorer

    boominXplorer Elite Ranger Elite Explorer

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    The band cannot tighten on the drum to fully engage the gear, the anchor is broken. It's still in there so it does something when you put it in reverse but will not "grab and hold tight".

    4x4 low gives you gear reduction and ease of movement at low rpm. If you hit the gas in 4lo I bet it will also slip but will do more than in just 2wd because of the gear reduction.

    Btw the reverse band is the same from like 91-2010 n the v6 transmissions.
     
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  8. The Swamp Fox

    The Swamp Fox New Member

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    Thanks a mil for the explanation! I was picturing a broken band no longer forming a circle, and was thus confused how my symptoms of still having *some* reverse could align with such a diagnosis. But if I'm following you correctly, you're saying the "ears" on the band are what form the anchor point that enables the tightening on the drum — so the anchor is sheared / broken, you have no tightening at all.

    Your comment explaining how the gear reduction in 4x4 Low would reduce strain / torque requirements on the tranny makes sense and confirms a hypothesis to that effect that I had read elsewhere. You're right inasmuch that my posted Road Test results indicate that there is still slipping in 4x4 Low when in Reverse, just not as bad as in 2WD.

    Appreciate the tip regarding reverse band compatibility across models as well. How involved is pulling the transmission, whether for a rebuild or just to swap in a different unit?
     
  9. boominXplorer

    boominXplorer Elite Ranger Elite Explorer

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    Unfortunately pulling the transmission is the easy part. The entire transmission has to be broken down to get to the band. If you have been driving like this for years I'd suggest a full rebuild as clutch material will be throughout the transmission.
     
  10. MotorCityFats13

    MotorCityFats13 Well-Known Member

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    my personal solution that I did for 3 years before I finally junked my 2nd gen was to always pull into a parking spot that I could pull straight out and when needed i had to push the truck backwards I had to be extra cautious in winter that I didnt get it stuck in a way that would require rocking it in reverse.... by the end the trans was reaching 200f on normal drives and 1st was starting to slip and then the engine started pouring out coolant from somewhere in the back of the block and didnt care to find out what let go
     

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