AX4N, No O/D - Flashing Light

Nick1994

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Working on my dad’s 2002 Mercury Sable, OHV AX4N, 206k miles.

Went to take it for a drive and it shifts fine, except when you get on the freeway it won’t go into overdrive, seems to be in 3rd. RPMs are over 3k at 65 mph. If I let off the gas pedal and coast, after 3-4 seconds the RPMs go down to around 1,500. If I give it a little gas to try to maintain speed it goes right back to over 3,000. If I drive over 70 mph it starts flashing the transmission warning light (yellow exclamation mark) until I turn the car off and on again.

Have tried disconnecting the battery for 20 min and reconnecting, same issue. No CEL codes are set or pending. Fluid looks fine, is in the crosshatch for level too.

This week we did some work to it, but I don’t think it would make a difference with this. It got new brakes, air filter, cabin air filter, bank 2 sensor 1 oxygen sensor, oil change, coolant change, thermostat, and MAF sensor cleaned.

Any ideas?
 
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Check the MAF sensor again. MAF sensor data is a critical element to proper torque converter clutch operation. MAF sensors can be finicky, cleaning them sometimes does cause them to fail, even if you’re careful.
 
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What happens if you use the gear shifter to manually engage/disengage O/D?

Does that also result in the slipping, flashing light, etc.?
 

JTK

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Did the transmission issues exist before you did all that work?

206K miles is a lot for an AX4N assuming it's the OE.

No codes pending or otherwise?
 

Nick1994

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What happens if you use the gear shifter to manually engage/disengage O/D?

Does that also result in the slipping, flashing light, etc.?
Shifting from O/D to D does nothing on the freeway. Only driving over 70-75 makes the flashing light come on.

Did the transmission issues exist before you did all that work?

206K miles is a lot for an AX4N assuming it's the OE.

No codes pending or otherwise?
I never drove it before, but my dad drives it long distances all the time and said the RPMs were always normal, like closer to 2k. And no flashing lights (75 mph speed limit on the freeway he drives, 200 mile round trip every couple weeks). No pending codes. It had a P1151 but after replacing the O2 sensor it seems it isn’t coming back.
 

JTK

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Is the vehicle in good enough shape for another AX4N?

We had a 2001 Windstar with the AX4N a long time ago. We only owned it until just over 100K miles though. That was an excellent vehicle for us oddly enough.. I did a pan drop and fluid change once when we got it around 36K miles as the original fluid was nasty. Those were the days. I bought that van in 2003 w/ 36K mi on it for like $12K.
 
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If I remember right, there is a cable that plugs into the shifter linkage on the transmission. One of the wires is responsible for OD, if it's damaged or loose on either end then you'd get the OD light illuminated at all speeds. I don't know if that's your case, but replug all the cables you removed or pulled.
 
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There is a wiring harness plug on the transmission that is under (below) where the brake master cylinder is mounted. Make sure it is in good shape and fully plugged into the trans
 

Nick1994

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Just scanned with FORScan, it has a P0734 and P1000

54A2D884-7537-4DEB-BB55-D7E2C3C5E01C.jpg


1EC89DE5-26DB-4042-8128-C22F7F8E4854.jpg
 
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That's basically how mine died. Maybe you'll get lucky and it won't be the torque converter going. Still drove it a while for a while after it happened but you get slightly worse gas mileage because you don't have a 4th gear. Low transmission fluid could also do it too but you said you already checked.
 
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Outside of a mechanical failure like a burnt 4th Band or 4th Band Servo issue that would require a rebuild....A mechanically stuck shift solenoid is a possibility.

However there isn't a Shift Solenoid failure mode that would result in having 1st, 2nd, 3rd with no 3-4 upshift. But if Shift Solenoid A were to be mechanically stuck OFF.....You would have 1st & 3rd.
The unit would stay in 1st through the 1-2 shift, Shift to 3rd on the 2-3 shift command, Then stay in 3rd on the 3-4 shift command.
See the stuck SSA chart below.

The Ford pinpoint test will have you backward engineering the entire car, Where a simple "Click Test" of the Shift Solenoids will suffice as a good start to diagnosing this.

A good Solenoid will have a sharp snap noise to it when activated, A mechanically stuck Solenoid will either make no noise or be very dull compared to the rest (Solenoids B & C).

P9phGHQ.png
 
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Nick1994

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Well I took it to a local transmission shop that's rated good online this morning.

They just called back and said there is some sort of internal failure with it, the tech can see everything on the computer while driving it and that it does try to go into 4th, but basically there's no 4th gear to go into.

Rebuild is a range from $1,895-$2,695 depending on how bad it is. I told them to go for it.

They said it might take 2 weeks to finish so we will see.
 
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