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Last Post 01 Dec 2014 07:36 PM by  bfetch
Expedition transmission issues - calling Steve H!
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bfetch
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14 Oct 2013 12:59 AM

    Yo!  Steve H!  

    I hope you don't mind me picking your brain.


    '05 Expedition, 5.4L, 128k, trailer-tow package.
    When driving (trailering/loaded or unloaded), uphill, the vehicle does not maintain speed. It continues to slow while I add more throttle, until it slows to around 40-45MPH when it finally downshifts.

    I can press the accelerator down faster (before it reaches 'degraded velocity'?), in an effort to get it to downshift, but it doesn't seem to be the right answer for this situation.

    I recently replaced both lines from the transmission to the cooler & radiator (rusted through, sprung leak) that required removing the radiator (and the quick disconnect fitting on the radiator)  so I'm wondering if I may have an obstruction somewhere in the fluid path.

    Referencing the FSM doesn't seem to help clarify troubleshooting required for this particular issue.  Any guidance is appreciated!

    Thanks,

    Brandon

    atcovan
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    18 Oct 2013 09:23 AM
    That's one hell-uv-a hill. Checked the fuel filter, fuel pump and air filter? What happens if you shift down manually?
    Steve Hoelscher
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    18 Oct 2013 05:01 PM
    Hey Brandon, I am not sure if I understand the circumstances completely. You can't get the transmission to downshift before it falls to 40-45 mph even when you apply more throttle? Or does applying more throttle cause the downshift but it doesn't prevent the loss of speed?
    bfetch
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    30 Oct 2013 10:12 PM
    First of all, thanks for reading & replying and accept my apologies for being slow on my own reply. :-)

    Fuel filter was replaced last summer. Uncertain on the fuel pressure (I have a gauge but the Exped has no place to test from that I know of). Air filter is a K&N - checked every other oil change. Can down-shift manually (OD off/on, D to 2...).

    As I approach the hill (from 65-75), I steadily add more throttle in an effort to maintain speed and once it reaches 55-60, continuing to add more throttle (beyond what you would think is needed) does not seem to improve speed or induce a down-shift until a whole lot more throttle input is given or it finally slows to 40-45. I can mash it and it will down-shift. If the hill is tall enough, it won't come out of that lower gear until we're well above 65 and or nearing the peak of the hill.

    Thinking more about the situation, I remembered these trucks are drive-by-wire (DBW) and a couple of years ago it threw a CEL noting "throttle return failure" (an entire trottle-body replacement == $300). Instead I removed the TB, opened the TB gear casing, cleaned things out, added some lube back in and haven't seen a recurrence of the CEL.

    There doesn't appear to be any clutch slippage, the fluid is changed every year (transmission & converter), and as noted above, after the pair of hose replacements there's been additional new fluid added.

    Am I dealing with a speed sensor issue? Throttle input sensor? Possible clogged fluid passageway causing a low-pressure situation in part of the valve-body (post hose replacement)? At this point I'm debating on bringing it to the dealership (have a good one I trust in-town) or the local AAMCO since we're going to need the truck for the winter.

    Thanks again for any ideas folks.
    Brandon
    Dick Rasmussen
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    31 Oct 2013 05:30 PM

    Brandon,

    What happens when you select the appropriate gear manually? That is, lock out overdrive (go to 3rd) or select 2nd? My much less sophisticated 1988 Dodge based Camper Van (3 speed auto) frequently needs 2nd selected manually so that I can tow up grades at part throttle without forcing a downshift or "slipping" the TC creating heat. Better in 2nd at 45 to 50 mph at part throttle than similar speed in 3rd with the converter working it's butt off. 

    Dick

    NOT Steve!

    bfetch
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    01 Nov 2013 12:44 PM
    Dick,
    The transmission will shift in/out of the selected gears without issue during cruising and towing.

    And your comment about 'slipping' in regards to the TC is where I may have messed up from the beginning: I thought I recall reading it's best to not downshift when towing but let the vehicle decide what gear it wants to be in relative for load/incline/speed.

    Thanks for the replies.
    Brandon
    Steve Hoelscher
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    21 Dec 2013 12:34 PM
    Sorry for the slow response. I don't often get over here and the last few months have kept me busy.

    This sounds like a classic TPS problem to me, especially in light of the CEL issue. I would put a scanner on it to monitor data and look at what he TPS is displaying while you are driving in these conditions. Its not uncommon for the TPS to get a bad spot in it or become non-linear in response. If its DBW the TPS is probably located on the pedal.

    I doubt you have any issue with the valve body or transmission itself.
    bfetch
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    01 Dec 2014 07:36 PM
    Holy thread from the dead Batman!

    So, you may find this illustrative or humorous - I happened to see it three ways at this point; + aggravating! :-)

    Come to find out, the capacity listing in both the FSM and the owners manual for transmission fluid has this nice little asterisk next to the "14 quarts*" listed. Reading the asterisk indicates something along the lines of "factory-installed supplemental cooling components (trailer towing package, heavy-duty package...) may increase the capacity levels beyond this total". So while I've been draining out and returning 14q worth of fluid, it's been running 2q+ (closer to 2.5q) low for most of the past 12 months!!!

    This won't excuse what caused this low-fluid situation (the busted trans line earlier in 2013 & my lack of filling-up the fluid) but after performing a full exhaust repair (manifold to tailpipe), I presumed (seriously incorrectly) that the transmission dipstick had been shifted/moved/altered in a way to read incorrectly afterwards.

    Stupid me.

    Now, to add insult to injury I experienced a strange occurrence with this 3v 5.4L where the #3 plug managed to back itself out (that was a 2v-specific issue). I think this was caused by my 'upper engine work' earlier this year (rockers/HLAs/phasers) and I didn't put 2+2 together... Anyway, this ended up triggering a flashing MIL (possibly dumping raw fuel into the CATs - no bueno) during a race weekend tow. R&R of the plug & COP (coil-on-plug) not only eliminated the MIL but dramatically improved the on-throttle performance and the lack of power/needed downshifts while cruising unloaded!! And the plug repair even eliminated what I perceived to be a rod/crank knock on that side of the engine too!!!

    With as happy as I am with its current performance you'd think it cured my of my knee arthritis too!

    Summary & takeaways:
    Always fill your fluids to the level indicated by the dipstick, never less.
    -stupid, stupid, stupid
    Never underestimate the tangential association of an issue to the root-cause of an observable fault.
    -rod/crank knock & transmission/truck performance behavior related to a single spark plug?!
    Go back to basics and review what was last done to a vehicle before dumping it on someone else to repair!
    -I had begun the process of building a 2015 EcoBoost F-150 & trading in the 'hunk of junk'!

    Very appreciatively to everyone who replied,
    Brandon
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