1999 Ford Taurus



May, 12, 2009 AT 12:39 AM

1999 Ford Taurus 6 cyl Front Wheel Drive Automatic 197000 miles

I bought the car and the front pump seal went out so had it and the torque converter replaced then on the test drive the speed sensor went out the guy put in used one, and it worked for a little bit then it went out. I put in new speed sensor and run ok for a little bit the she speedometer started jumping again around an the car would shift into low gear you can shut it off and it would work for a little while. So I replaced the pig tail connector on that speed sensor still the same problem. So I replaced the other speed sensor on the driver side of the car the car run good I drove it 50 miles without any problems the next morning the speedometer was jumping around again. So I rewired the there speed sensor on the back side of the motor that I put the new pig tail I did this due to the wires being so brittle. Still the same problem. So thinking I may have got bad vehicle speed sensor I got another one and still the same problem speedometer jumping around and shifting erratically.


8 Answers



May, 12, 2009 AT 9:35 AM

Hi fireman6,

Thank you for the donation.

Erratic shifting points to a fault in the VSS as it supplies signals to the PCM.

There are different models with different transmission installed and I would need to know what is the engine and transmission model code to get the correct data.



May, 12, 2009 AT 12:58 PM

It a 3.0 flex fuel and has an axode tranny the only code it kicks out is a egr valve sensor low voltage. But have found out that it is the gear that drives the vss what is the possibility that it is only that gear and not deeper into the tranny. The gear is the one in the pod on the backside of the tranny that drives the vss



May, 12, 2009 AT 1:39 PM

Yes, it should only be the VSS or its circuit malfunctining that is causing the trans shifting erratically.

What is the DTC that you are getting?

The other sensor that you are refering to should be the Transfer Case Speed Sensor (TCSS )



May, 13, 2009 AT 8:45 AM

It was a 1400 which is the egr valve sensor low voltage. The tranny is the axode the vin on the car is 1fafp5322xg229822 if that helps also check the spedo drive gear and everything is good but still the spedometer jumps around and still shifting irradically



May, 13, 2009 AT 11:21 AM

For the speedometer and trans to act funny, there should be DTC stored.

Here are the diagnostic procedures.

NOTE: After each service or repair procedure has been completed, reconnect all components. Clear DTCs and perform OBD-II Drive Cycle. After drive cycle is complete, repeat QUICK TEST procedures to ensure all EEC-V systems are working properly and DTCs are no longer present.














May, 28, 2009 AT 9:33 AM

Since talking with you I have taken the car to ford for a diagnostics and they said it was the gear in the pod that drives the VSS changed that and still the same thing so changed the gear on the speed sensor still the same thing. Drove the car with the mechanic while the diagnostic cpu was hooked up showing that it was in 2nd gear low speed only code it was kicking out was for the dpfe sensor after a litlle bit it lined out run good stopped and shut the car off and restarted finally done it again and finally kicked out the vss code reset it and still the same thing. They thought maybe wiring and had me jump from the pcm straight to the VSS and still the same thing. So I took it back to ford for them to reflash the pcm they said they couldnt reflash the pcm cause it had the most current program. And told me that I needed to replace the gear on the output shaft on the tranaxle, I asked how do they know that that is the problem and the clerk said he would not know until they tore it apart. And I dont want to do this unless it is a sure thing due to the cost of tearing down the tranny again. Need help and guidance on this bad thank you



May, 28, 2009 AT 11:07 AM

I am afraid I am not able to assist much as I do not have hands on experience on this problem. Some problems requires the trans to be stripped to know what has gone wrong.

I have posted this poser in the moderators forum and my fellow technicians should be able to come up with some answer for you.

Do you know of the exact trouble code that was retrieved by Ford technicians?

In the meanwhile I would like to apologise for keeping you waiting.



May, 28, 2009 AT 9:42 PM

Here is more info on the probable failure of the tranny.

The Ford AX4S automatic transmission is a four-speed electronic overdrive transmission used in 1995 to 2000 Ford Windstar minivan. The transmission is also used in 1991 to 2003 Ford Taurus and Mercury Sable, and 1993 to 1995 Ford Taurus SHO models. The AX4S is a second-generation version of the AXOD and AXOD-E transmissions used in 1986 to 1991 Ford Taurus.

The AX4S transmission still shares the same AXOD end cover as the older AXOD transmissions, which makes identification somewhat confusing, but it saved Ford the cost of retooling the cover. The transmission also has a 17-bolt pan on the bottom, which is different from the 19-bolt pan used on the newer AX4N transmission that replaced the AX4S in 2001 on the Windstar.

The reliability of the AXOD, AXOD-E and AX4S transmissions has been very poor, with transmission failures at relative low mileage (60,000 to 100,000) being fairly common. According to the Center for Auto Safety, the failure rate for these transmissions has been significantly higher than that for most other automatic transmissions.

The high failure rate has been blamed on inadequate internal lubrication of critical parts, and a weak forward clutch piston that cracks and leaks pressure. Ford scrimped on the forward clutch piston, making it out of cast aluminum until 1995, when they switched to a steel part due to all the trouble they were having with this transmission.

Ford TSB 94-24-7 covers replacement of this piston with a stronger steel piston.

Ford has so much trouble with the earlier versions of this transmission that in 1995 it extended the warranty on 1991 Taurus transmissions to six years or 60,000 miles. That's ancient history now, and the Windstar transmissions were only covered by the standard powertrain warranty.


The AX4S transmission contains two planetary gearsets and a combination planetary/differential gearset. The operation of the planetary gearsets is controlled by four multiple-plate clutches, two band assemblies and two overrunning clutches. Hydraulic pressure is provided by a variable displacement pump driven by the torque converter.

The transaxle has a large chain drive on the driver side end under the cover with AXOD stamped on it. There are also three hydraulic accumulators, one for neutral/drive, one for 1st and 2nd gear, and one for 3rd and 4th gear (overdrive).

There is also a thermostatic fluid control valve inside the transmission that compensates for fluid expansion as the fluid gets hot. When the fluid is cold, it routes more fluid to the main control body. As the fluid heats, up the valve slowly opens to allow some of the fluid to drain back to the sump. This helps keep the fluid level below the rotating parts of the transmission so it doesn't foam and become aerated (which can cause erratic transmission performance).


The transmission is controlled by the powertrain control module (PCM), using inputs from the transmission sensors, vehicle speed sensor and other engine sensors. Key components include: The Transmission Control Switch (TCS) is on the end of the gearshift lever, and is used to turn overdrive on and off. For normal driving, leave the transmission in overdrive. If the TCS button is pressed, the PCM will turn on the Transmission Control Indicator Lamp (TCIL), which is the O/D OFF overdrive light. This will prevent the torque converter from locking up or the transmission from going into 4th gear while driving. This increases available torque but also reduces fuel economy.

NOTE: If the overdrive light is flashing, it means the PCM has detected an internal electronic fault in the transmission. Some people call this the "sell or trade this vehicle now" light because it usually means the transmission is failing.

Turbine Shaft Speed Sensor.

The Turbine Shaft Speed (TSS) Sensor is a magnetic pickup that monitors the input speed of the turbine shaft for the torque converter. The computer uses this information to control torque converter clutch lockup and internal transmission operating pressures.

The Output Shaft Speed (OSS) Sensor is another magnetic sensor that monitors the speed of the transmission output shaft. This signal is also used to control the torque converter clutch, gear shifting and internal pressure.

Shift Solenoids SSA, SSB and SSC control the operation of the three shift valves. The solenoids are located in the main control valve body, and are two-way, normally open solenoids.

The Transmission Fluid Temperature (TFT) Sensor, located on the main control body, monitors the temperature of the fluid. The PCM uses fluid temeprature to modify the shift characteristics of the transmission when it is cold.

The Electronic Pressure Control (EPC) Solenoid controls the hydraulic pressure inside the transmission by balancing the line pressure against the modulator pressure. The PCM has an adaptive strategy that allows it to modify the shift characteristics over time for smoother operation. If the battery is disconnected, these learned settings go away and the PCM has to start all over again, which may cause harsher shifts for several hundred miles until the PCM sorts things out again.

The Torque Converter Clutch (TCC) Solenoid controls the lockup and release of the torque converter clutch. Problems here can make the transmission feel jerky at low speed if the torque converter locks up too soon or fails to release soon enough, or cause a drop in fuel economy if the converter never locks up.


The PCM controls the upshifts and downshifts of the transmission based on vehicle speed, load and engine rpm. The transmission will downshift to a lower gear when the vehicle is slowing down, when an increase in the load on the transmission requires a higher gear ratio (as when driving up a steep hill), or when the accelerator pedal is floored (kickdown).

If the transmission downshifts harshly gong from 3rd to 2nd gear, or shudders when accelerating around a corner, the problem may be air in the transmission fluid caused by a low fluid level. Ford TSB 99-18-4 covers this problem and says the fix is to check the fluid level (after the vehicle has been driven, the fluid is hot, and the engine is idling in Park), and add fluid as necessary to bring the fluid level up to the full mark.


The type of automatic transmission fluid (ATF) used in these transmissions is very important for proper transmission operation. Always refer to your owner's manual or the marks on the dipstick for the type of fluid to use. Up to 1998, the AXOD, AXOD-E and AX4S transmissions require Mercon ATF. Starting in 1998, all Taurus and Sable vehicles require the newer Mercon V fluid. On 1998 Windstar models built prior to 9/9/2007, regular Mercon is specified, while those built after this date require the newer Mercon V fluid. Ford warns that using wrong fluid or a fluid that does not meet their Mercon or Mercon V specifications can cause transmission problems and possible transmission failure.


Transmission diagnosis is usually not a job for a do-it-yourselfer. It takes expertise and special equipment to properly diagnose a transmission problem. Here is Ford's recommended procedure: 1. Check the transmission fluid level. Many problems such as slipping, slow engagement and erratic or sloppy shifts can be caused by a low fluid level. If low, add the proper fluid to bring the level up to the full mark. Also inspect the transmission for leaks, and fix as needed to prevent fluid leaks.

2. Check the harness connectors for proper installation at the Transmission Range (TR) sensor, Turbine Shaft Speed (TSS) sensor, Output Shaft Speed (OSS) sensor, and transaxle top connector.

3. If the Check Engine Light is on, connect a scan tool to the vehicle diagnostic connector and check for any transmission-related fault codes.

4. If the Check Engine Light is OFF, and there are no fault codes, go to Step 5. If fault codes are present, refer to the appropriate Ford diagnostic charts and perform the required step-by-step checks to isolate the problem.

5. If the transmission is still having a problem, connect a Ford Transmission Tester (Rotunda 007-00085) and follow the appropriate tester instructions to determine if the problem is internal. Essentially, this involves checking internal transmission pressures and the operation of the various sensors and control solenoids.


Based on the poor reliability record of the AXOD, AXOD-E and AX4S transmissions, problems such as slipping when driving at a steady highway speed, harsh shifts or erratic shifts, transmission noises, etc. Usually mean your transmission is failing and repairs will soon be necessary. In most cases, that usually means replacing the transmission with a rebuilt unit.

An early symptom is often a noticeable change in engine rpm of 200 to 300 rpm while driving at highways speeds in overdrive. This is often due to the transmission losing lockup pressure.

Replacing a transmission on a Windstar or other front-wheel drive Ford is a difficult job, taking 8 to 12 hours depending on the skill level of the person doing the job, and how much trouble they run into with old, rusty fasteners. The engine has to be supported from above while the transmission and lower suspension components are unbolted and lowered to the ground. A rebuilt transmission nowadays typically costs $1500 to $1950 or more depending on where you get it, but I have seen rebuilt AX4S transmissions advertised on ebay for as little as $600 to $850, plug shipping (add another $150 to $250 plus a core deposit of $300 or more for your old transmission).

My advice if you need a transmission is to deal with a reputable transmission shop, independent repair garage or Ford dealer who will guarantee their work. A quality rebuilt transmission should come with a two year or longer warranty. The total job should not cost more than $2200 to $3000 (the price will vary depending on the shop's hourly labor rate, and the cost of the rebuilt transmission).

Hope this was Helpfull


Please login or register to post a reply.

How to gather codes Ford Explorer
Code Read Retrieval/Clear Scion XD
Code Read Retrieval/Clear Chevrolet Camaro
Code Read Retrieval/Clear - Dodge Stratus
Code Read Retrieval/Clear Mercedes Benz
Read Codes Like a Pro
 Step by Step video GMC Yukon XL 2000-2006
Code Read Retrieval/Clear