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bubbe11

2008 Lincoln Navigator 2WD Randomly downshifts towing trailer & wrench light comes on

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While hauling our TT on highway at 65 MPH (within weight limits), the transmission downshifted to 3rd gear and would not come out. The wrench light came on dashboard. When I shut down Navigator, wrench light went off and then everything returned to normal. Transmission shop rebuilt tranny, installed new torque converter and heavy duty discs. Also put in new alternator and condenser. After rebuild, the problem returned and the mechanic road tested and could not find a problem. Mechanic cleared all codes and test drove with TT with no problems. Next time out, exact problem came back. Took it back to transmission shop and they installed a new torque converter and replaced a suspected valve. Test drove with TT problem returned, wrench light on dash and downshift. Same solution. Pull off; shut sown; everything returns to normal. At a loss. Any Ideas will be greatly appreciated.

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This may sound simplistic, but please try it if it hasn't been done.  Expy/Navy was new in 07 and Ford keeps updating the PCM programing for several years after introducing a new model, to fine tune engine and transmission performance and address issues/complaints.  Dealers will not automatically recommend reflashing your PCM while it's in for service or state inspection.  My dealer even balks about doing it when asked.  I decided to have my 09 Expy reflashed to the latest (and last) version two years ago.  When I asked them to check if I had the latest version they asked why and what problems was I having.  I told them I just wanted the latest version and I was willing to pay the 120 bucks to have it done.  Turns out it was several versions behind and they had to reflash it twice to get the latest version (no extra charge).  But boy what a difference... as soon as I started down the road it felt like an entirely different vehicle. The rough/confused transmission shifts were gone forever... the engine and tranny now work together in perfect harmony.  Even the occasional problem of getting a hard brake pedal when backing out of the garage in the morning has never happened again...  because the reflash increased the cold idle rpm to bring the brake booster vacuum up quickly.  I also saw a consistent 1.5 mpg improvement.  Two years later and I'm still impressed with how silky smooth and refined my 09 Expy drives now.  I should've had it done much sooner and since then I've had all our vehicles checked/reflashed to the latest PCM versions.  It fixed our Fusion Hybrid wrench light problem when driving uphill at freeway speeds on a hot day... which would reset without a fault code on restart.

Edited by CoolScoop

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That's great advice for a lot of people. I don't think the general populace realizes how fragile some cars' computer electronics are  - one file corruption or improper data entry and you get bad juju. If you have a newer Jag, get ready to live and die by the reflash. And in my XK a reflash solved a temperature problem. In my Cad it solved the auto-highbeam issue. And from what I read in reviews about the Nautilus, I would guess that the newer ones must have updated transmission  programming because my tranny works awesome, none of the reported reviewer issues in sport mode. It just sucks when you have to pay for it....

 

Remember that Mars Lander that crashed because the programmer programmed the descent in pounds of force rather than fig newtons. Ouch. 🚀

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I forgot to to add the most import thing for the OP.  I also saw a big improvement in tow haul mode after the reflash... it appears they totally rethought how that feature works.  It shifts much better and at the proper time now, including downshifts when braking or going downhill for engine braking.  

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5 minutes ago, bubbe11 said:

CoolScoop - thanks so much for your reply.  Will definitely look into this ASAP.

Hope it works... keep us posted!

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On 2/9/2020 at 2:28 PM, Deafsoundguy said:

That's great advice for a lot of people. I don't think the general populace realizes how fragile some cars' computer electronics are  - one file corruption or improper data entry and you get bad juju. If you have a newer Jag, get ready to live and die by the reflash. And in my XK a reflash solved a temperature problem. In my Cad it solved the auto-highbeam issue. And from what I read in reviews about the Nautilus, I would guess that the newer ones must have updated transmission  programming because my tranny works awesome, none of the reported reviewer issues in sport mode. It just sucks when you have to pay for it....

 

Remember that Mars Lander that crashed because the programmer programmed the descent in pounds of force rather than fig newtons. Ouch. 🚀

This is the same reason the dealer won't use forscan to do something such as change the mirrors on an F-150 to self fold, or any of the dozens of other code changes to make things work differently from the factory programming. If they screwed something up, Ford wouldn't pay the dealer to fix it under warranty.

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@CoolScoop    I can't thank you enough for your advice.  We took it back to the transmission place and they ran the updates for free.  Took over 1 1/2 hrs. for all of them to update.  Test drove car today with trailer hooked up.  Success, success, success!!!!  Again, many thanks - you're a lifesaver!

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4 hours ago, bubbe11 said:

@CoolScoop    I can't thank you enough for your advice.  We took it back to the transmission place and they ran the updates for free.  Took over 1 1/2 hrs. for all of them to update.  Test drove car today with trailer hooked up.  Success, success, success!!!!  Again, many thanks - you're a lifesaver!

You're quite welcome.... I'm really glad it worked out!  You should also see a nice improvement in normal driving... it may take a few days for it to learn/adjust to your driving style!

Edited by CoolScoop

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@CoolScoop - Sad news.  Went on our planned camping trip today and made it one exit on the expressway when the same dang thing happened.  Wrench light came on, stayed in 3rd gear.  Exited the expressway and pulled over.  Turned engine off.  Turned engine on and wrench light went out and car was fine.  We didn't go back on the expressway.  Stayed on local roads to get home.  We'll call the transmission place tomorrow but if you or anyone else has any ideas, please let us know.  Everyone is stumped!

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They need to pull all the codes out of all the modules. There will be stored codes that helps determine what the computer is seeing that makes it go into limp mode. 

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