98 windstar ax4s tranny?


rjhansen
06-29-2011, 08:15 PM
The van shifts perfectly when cold, when driving for awhile all temps are up to temp, the tranny will buck, and shift erratically, upshift, downshift whatever it feels like then just go into 2nd gear and stay. Trans fluid is perfectfully level, and bright cherry red! No O/D LIGHT FLASHING, NO CEL ON. I'M CONFUSED..... I'VE BEEN LURKING AROUND THIS SIGHT FOR AWILE READING EVERYONE ELSES POSTS AND I DON'T KNOW WHERE TO BEGIN!! WISWIND ANY ADVICE? THE VAN IS 3.8, AX4S TRANNY WITH 106K MILES ORIGINAL TRANNY, BLUE SERVICE TAG ON TOP OF TRANNY! THANK YOU FOR READING AND HOPE TO HAVE SOME GREAT ADVICE!:runaround:

olopezm
06-29-2011, 09:17 PM
Is the engine running ok? Rough running, anything?

AFAIK, from the shop manual, the PCM relies on engine sensors too to control the pressure and shifting of the transmission.

Do you have any access to a live stream scanner to monitor the VSS readings? Maybe it's going bad I think yours has the cable driven speedometer and even when it works ok the electrical part of the vss might be bad. That's why you need the scanner.

Oscar.

rjhansen
06-29-2011, 09:46 PM
Van runs perfectly!! No problems.......... Could it be the 1 of the shift solenoids? I talked to 1 tranny shop and mentioned that the intermediate drums were a common failure on this tranny?

grog11
06-29-2011, 11:19 PM
Wonder if the pcm computer module starts to heat up and then one of the electronic components gets weak and fails?

My other thought is an internal piston seal is hard when cold, and then heats up, softens, and seal does not hold against the cylinder wall,then transmission line pressures fall.

Valve body bolts may need to be torqued again, and are expanding open when heated, allowing the fluids to not follow the correct channel.

The PCM Computer uses the EPC valve to sense low line pressures, and PCM compensates by downshifting to get a higher line pressure.

wiswind
06-30-2011, 07:53 PM
Staying in 2nd gear is "limp mode".
The PCM has sensed a problem with the transmission and will not let it shift above 2nd gear.
A diagnostic would be the way to go.
You might get lucky and have a OBDII code set......which can be read with a Generic OBDII code reader......which many auto part stores will do for you for free (make sure to ask for and write down the numeric code that comes up).
If you don't have a OBDII code set, then a more involved diagnostic with more advance equipment would be needed.

Common failures that are not expensive are the Transmission Range Sensor (TRS) aka Neutral Safety Switch, which is on top of the transmission.
The TRS is what the cable from the gear select lever connects to.
The other common and not expensive failure is the Vehicle Speed Sensor (VSS) which is on the back side of the transmission, above the forward most catalytic converter.
This is not an expensive part, but is difficult to access to change.
If you have the mechanical speedometer on your '95-98 windstar, follow the speedometer cable down to it.
It can be accessed from below.
The VSS has 2 parts, the mechanical part that drives the speedometer cable and the electronic part that sends a electrical signal to the PCM to tell it how fast the vehicle is moving.
For this reason, you can have the speedometer (mechanical version) working perfectly and STILL have a bad VSS.
I know this from personal experience.

Another part that is not expensive, but not as common to fail is the Turbine Speed Sensor (TSS)....aka intermediate shaft speed sensor.
The TSS senses the speed of the shaft coming OUT of the Torque converter.
This sensor has been confused with the VSS.......
The TSS is located on the driver's SIDE of the transmission, next to where the driver's side driveshaft comes out of the transmission.

The transmission is controlled by the computer.

The computer (PCM) needs to know the speed going INTO the transmission (which is the input to the torque converter).
It gets this from the tachometer....engine speed.

It needs to know the speed of the shaft coming out of the torque converter, to know how much slip there is in the torque converter.
This will be the speed INTO the gears (1 through 4).
It gets this from the Turbine Speed Sensor (TSS).

It needs to know the speed of the output of the transmission.
It gets this from the Vehicle Speed Sensor (VSS).

It needs to know what gear you have selected.
It gets this from the Transmission Range Sensor (TRS)

If it looses one of these inputs, it will have difficulty in controlling the transmission.

Fluid level and FLOW could be checked.
If there is any crud restricting the fluid flow through the in-radiator transmission fluid cooler, then it will cause the transmission to overheat and fail.
It does not flow very fast at idle......I think that the minimum flow required at idle is 1 quart in 45 seconds.
I seem to remember 20 seconds being normal on mine.

Once you get inside the transmission, the price and difficulty go up real fast.
Many shops are reluctant to mess with a transmission......for good reason.
Once they open up the transmission to do a repair, they "own it".....in other words, if something else happens, the customer will be back and very unhappy.
Once 1 thing fails inside a transmission, it is common for many other things to be on the verge of failure.....as many problems seem to crop up around 100K miles, many folks have never changed the fluid (should be changed AT LEAST every 30K miles) and even if they have changed the fluid, many parts of the transmission could still be stressed from other parts wearing/failing.

rjhansen
07-19-2011, 03:02 PM
Well the van went to the tranny shop lord and behold the clutch packs were shredding apart lots of metal in the pan and torque converter:headshake.I now have a fully rebuilt trans, that I might say didn't cost an arm and a leg!! $1350:).

wiswind
07-19-2011, 08:41 PM
It is CRITICAL that the flow out through the in-radiator transmission fluid cooler be verified to make sure that the flow is not restricted by junk that came out of the clutch packs.
If this flow is restricted, it WILL cause the transmission to overheat, which leads to failure.
It is standard procedure in the FORD documentation for transmission service when replacing or rebuilding a transmission, so it is possible that your shop did this.

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