AX4N shifting issues

'02 Taurus SES, 3.0L Vulcan, AX4N, 140K miles.

The car drove normally the other day, but now the transmission won't shift into drive. Actually, I've been able to get it to shift to drive by easing back on the accelerator, but it will shift back to the next lower gear as soon as you attempt to get back on the gas.

I dropped the pan today to check for metal fragments and found nothing out of the ordinary, just the normal graphite-like sludge around the magnet, maybe about 1/16" or so thick. This leads me to believe that the transmission has not (as of yet) begun to consume itself.

The OBDII is throwing a code of 0750, which is SHIFT SOLENOID A MALFUNCTION. Don't want to deceive myself in thinking this is something simple, but could this fix be as straightforward as going in and replacing the shift solenoid?

I did a little investigating (not sure if I came up with the correct info, though) and found some info regarding testing the solenoid coil resistance. Disconnected the trans harness and took some continuity readings between the pins. Here's what I was able to obtain.

PIN 2 to PIN 1 3.6ohms
PIN 2 to PIN 6 15.6ohms
PIN 2 to PIN 8 16.6ohms

If my test method is correct, these readings are showing that the coil associated with PIN 1 is weak.

If anyone has any experience in this area, I would greatly appreciate all of the input that I can get. Thanks Rob

I called a trans shop to get an idea of what they would charge to replace a shift solenoid; $600+ . They told me that the trans has to be pulled to perform the repair. I found a procedure where one can replace the valve body with the trans in place (although the transaxle mount needs to be removed).

Anyone ever try this with the transmission in place?

Are you positive on the model year and transmission? I checked the factory service manual for the 2002 Taurus/Sable. The manual only lists two transmission options, the 4F50N and the AX4S.

-Rod

pretty sure about the model and year. The transmission pan has AX4N METRIC stamped in it. Also called the Ford dealership to verify by the VIN.

Took some additional resistance readings associated with the three analog shift coils, and here are the results taken from the 10 pin connector on top of the trans.

PIN 1-PIN 6 16.6 ohms
PIN 1-PIN 8 17.6 ohms
PIN 6-PIN 8 37.7 ohms

The previously posted readings coupled along with these only reaffirm my previous thoughts of the A coil (PIN1) being weak, provided that the test points used are correct. Does anyone agree with my findings?

I had to go back to 2000 model year to find a Taurus listing the AX4N transmission. Scrolling through the diagnostic procedures for the transmission I eventually came across a pinpoint test that tests each shift solenoid for resistance. Per that section, each shift solenoid should measure 20-30 ohms across the two terminals. Looking then at the transmission valve body connector pinout:

SSA is between pins 1 and 2,
SSB is between pins 6 and 2, and
SSC is between pins 8 and 2.

Again, this is per the 2000 model year factory service manual so I cannot guarantee that any of these values would be the same for your 2002 model year, but they do seem to align with what you previously found.

-Rod

Re: AX4N shifting issues [In reply to] Sign In


Got some additional readings.
PIN 7-PIN 10 (EPC) 3.4ohms
PIN 7-PIN 3 (TCC) 12.8 ohms
Could not get a reading other than very high resistance (approx. 100K ohms, but definitely moved off of infinity, so not open) using an analog multi meter (the digital fluke meter that I used for all of the other readings only indicated OL and is auto ranging, so I went to the analog). Was told by an auto tech that I need a scan tool to check the thermistor. Started the vehicle and let it warm up for about 10 minutes, nothing indicated on the dash other than the ABS (and I've come to find out that it's been on for a while). Checked the fluid level to make sure OK.
Took it out for a spin with some peculiar findings:
-made the 1-2 shift at 13mph/1750rpm
-made the 2-3 shift at 22mph/1750rpm, the check engine and service transmission lights both came on, transmission remained in 3rd
- decelerated to the stop sign at the end of the block
Drove it around the neighborhood where I could get the speed up a bit and test the shifting some more. As before, the trans made the first two shifts, then made the 3-4 shift at 32mph/1900 rpm, remained in 4th near 35mph for about a couple hundred yards, then down shifted as if going into safe mode. Drove around several blocks with varying results, sometimes shifting normally and other times not wanting to.
Got back to the house and immediately checked the codes. This time throwing 3:
0743 torque converter circuit electrical
0750 shift solenoid A malfunction
0760 shift solenoid C malfunction


Forgot to mention, also thought I could see a bit of trans fluid in the pinout when I disconnected the harness, so I hit it with electrical contact cleaner and then swabbed it clean and dry with a Q-tip. I also cleaned the connector on the harness end. I did not damage/bend any of the pins.


These findings really have me scratching my head. Remember that I really have no real knowledge of transmissions, but it seems to me as if the TCM (if that's what Ford uses to control the output to the trans) doesn't really know what it's doing. I say that based on the fact that when it's supposed to be in safe mode, it is still making shifts when it shouldn't be. Then, to have these separate issues crop up after basically doing nothing other than drain/refill.


Any thoughts? Also, I have no idea what the resistance readings should be for the EPC and TCC solenoids.

Transmissions are not an area I have experience either. I have the factory service manual which does identify some sensor and solenoid expected resistance values and shift speed ranges. If you are interested in the transmission troubleshooting section from the service manual, send me a private message with the vehicle details, specific request, and an e-mail address that I can send the PDF sections to.

-Rod

OK, so the job of removing the valve body cover with the trans in place is a bit tricky, but it can be done.
The hardest part was in removing the isolator because of clearance issues. I wound up completely removing the driver side rear main cross member bolt and then just backing off on the passenger side bolt about an inch. Once that was done, I used a pry bar at the rear driver side attachment point to gain the necessary clearance (for some reason I wasn't able to break free the front driver side main cross member bolt, and was afraid of breaking it, but backing it out would have helped the clearance issue tremendously for the removal of the isolator). The engine sub frame took a little finagling to remove, but it can also be done.
Upon removal, it was obvious that the A solenoid had an issue because the melamine cover that shrouds the exposed coil windings had been distorted and the cover was lying in the bottom of the pan........... about 1/3 of the coil was badly burned and chunks of the insulator at that end of the windings were also found in the pan and on top of the B solenoid's coil shroud. I'm amazed that it even functioned at all.
The A and B solenoids are located in very close proximity to one another, within about an inch and a half or so. The shroud cover over the B coil was also somewhat darker and I wasn't sure if it had received excessive heat from A's failure or if it was starting to exhibit signs of failure, so I replaced it also even though the coil's resistance was within spec. This has been a city car all of it's life so it's easy to see why the A and B coils would bear the majority of the work load.
The C solenoids shroud looked normal, and due to availability of 3 new solenoids within my allotted time to complete the task (a cold front blew in with frigid temps and rain turning to snow as I'm working in the driveway under a makeshift tarp), I opted to leave that one in place. Once back together, the trans now shifts like a champ.
Can't say how grateful I am for all of the excellent input as to how to tackle this job. I got the trans-in-place r/r procedure from another forum and would like to make reference to that for someone else's benefit, but am not sure if that is against site policy. Would also like to make reference to the other forums I used to gather the info that I needed as I believe that it would be quite valuable to another individual experiencing this same issue. If anyone is interested in pics of the 2 solenoids removed, I can post those at a later date.
Once again, thank you so much! Rob

BTW, it appears that the AX4N and the 4F50N transaxles are one in the same, according to Wikipedia. The AX4N was renamed 4F50N in 2001 without any changes being made. If anyone is interested in how the AXOD evolved into the 4F50N, just Google AX4N transmission and select Ford AXOD transmission-Wikipedia

I'm glad to hear you were able to get this repair done in your driveway and that the work you went to repaired the car. Thank you for following up on your thread!

The Forum Guidelines (http://www.automotiveforums.com/vbulletin/guidelines.html) state that linking to other forums is not allowed, so I appreciate you asking before inserting the links.

-Rod