Transmission slipping, seems OK when not in O/D

My transmission just started slipping on the way home today. It happened when it was trying to go from 3rd to 4th gear. I checked the transmission fluid and there was no burning smell and the oil was clean. Also the transmission fluid was at the proper level.

When I took it out of overdrive it seemed to run OK. I called a couple of transmission repair shops and they stated that it seems to be an issue with fourth gear, and that is because it runs fine when out of overdrive. They also stated that 4th gear is only used in overdrive.

They also stated that it is not safe to drive with the car out of overdrive. Is this true or are they just trying to get a transmission repair out of me? I also saw on here that the throttle position sensor can sometimes cause this.

Any helps or thoughts would be appreciated.

Did the O/D light on the gear select lever flash?
If so, try having the codes read to see if the code shows up.
Get the actual numeric code.

If not.....I really don't know.
If the fluid has not been changed within the past 30K miles......then I would try that, as it is likely not up to par.

I don't know what year you have....but Mercon V is now listed for all years as per a FORD TSB.
You can use Mercon in the years that it was called for only.......
One easy to find ATF that has worked for me in the past is Mobil 1 ATF.

Sorry it is a 1998 3.8l. engine.

I would go with the Mercon V fluid, which the Mobil 1 is rated for.
It is a synthetic, which will give better cold flow and better heat tolerance.
A pan drop and filter change during the process will give one a chance to look for abnormal material.
It is normal for there to be some grey sludge around the magnet...but any chunks of stuff is bad.
I have pictures posted of my tranny fluid change, which should be very similar to your '98.
Mine is at 1 year change interval, maybe about 20K miles, without the remote inline filter that I now have.

The fluid change may or may not solve the problem, but has in many cases taken care of problems....and is about the cheapest thing....and needs done anyhow....and give you a chance to inspect in the pan.
You can take pictures of the inside of the pan when you drop it......in case you need to see a tranny technician for further help.

update...can't get tranny out of first after the car has been running hot for an hour or so.

4life

Did you get the codes pulled? I had a VSS (Vehical Speed Sensor) go bad and the trannie was doing wierd things... ie...poor shifting..,...not shifting...

I didn't think the VSS was bad because I had replaced it only a couple of years ago when I got the van and did the headgaskets.

The van shifts a lot better now. It stills hangs and slips in first gear if I get on it from a stop. That doesn't give me confience to pull out on a busy road.

Regards

Dan

Update - I have read on here that the Throttle Speed Sensor could cause the tranny to slip. I tried checking the voltage out on it and traced back to a rectangular metal box where the Throttle Speed Sensor and the MAF Sensor go into. I got a -5 volts. Also I have had 2 mechanics say it is probably a mechanical issue and two other mechanics say that it only needs a fluid change. I am hesitant to change the fluid though because I have read that if the tranny is going a fluid change will put it over the edge.

The only codes from the CEL I am getting are for the IMRC's and the Fuel sending unit.

Lastly, the windstar runs fine until it has been driving for around an hour and then it seems it will not shift out of first.

I am hoping to avoid an $1800. rebuild that my mechanic has quoted me.

Any help will really be appreciated.

A fluid change will not repair damage that is already present.....so NO....it is not for certain going to solve your problem.
I WOULD change it, however.
Now.....It is supposed to be changed at least every 30K miles.
If this has not been done, there is a possibility that the new fluid, with its robust additive package, will clean a lot of stuff from the transmission.
If it has not been changed at the correct (or nearly so) interval, then it may require several changes.....say, 1000 to 1500 miles apart.....including a filter change.
Another approach that may work is the one that I use......
I installed an inline Magnefine filter (5/16" size) in the cooler return line.
You could have the new fluid change with the install of the filter, then change the inline filter afte the miles that I mention above.
If you have so much crud that the inline filter becomes clogged, it has a pressure bypass feature that will bypass the filter when it becomes clogged.
You can buy the filter from www.rockauto.com

Hi, From the way you are approaching your problem and the replys so far, I think you have been listining to a lot misleading info, Why not approach the problem sensibly and have the transmission diagnosed with the proper equiptment at a dealer service department? This way you won't be running around in circles..Good Luck,, Clay..

I don't think a throttle position sensor will cause transmission slippage.
After working on my vehicle, I had left the TPS unplugged when I took it for a short test drive.
Of course, it lit the CEL.
However, it shifted into all the gears without any slippage.
The 1 thing that I did notice is that the shift points were different, and it did not have any kick down when I pressed down on the accelerator (often called going into "passing gear").

As advised, going to a shop that can do a good diagnostic would be the way to go.
It is what I would do.

Beyond routine maintenance of changing fluid and filter, you will be just guessing, as there are a number of things that could be causing the problem.
Not all transmission codes will come up on the generic OBDII code scans, and will require more specialized equipment to read.

As I mentioned about front end checks, some things are best left to mechanics with the specialized equipment to do the job.
The transmission is electronically controlled, with a number of sensors, and solenoids, etc involved.
If you are lucky, the O/D light was flashing, which would mean that there is a code that they will be able to read.....which a good mechanic will be able to use to get to the root cause of the problem.

The intermittent nature of the problem (occurs after a warmup period) could point at the Transmission Range Switch. If the computer (PCM) thinks that the TRS is tellin it to be in first gear, then it will only allow first gear.

This switch has a couple of other names. The one used by the transmission shop that I went to is the Prindle switch (think of PRNDL as an acronym).

This switch is fairly easy to get to and runs in the $30 to $60 range.

The TRS (Transmission Range Sensor) is listed under the name " Neutral Safety Switch " at many auto part stores.
It is the same unit.

You can see the location of it in one of my pictures.......under the air filter / MAF unit....and flex hose.

Thanks for all the great help! Only question I have, when I went to get the Transmission Range sensor at Autozone, the counter guy told me that this part is located on the transaxle bell housing. What and where is the transaxle bell housing or is the service guy mistaken???? I trust this forum more than the Autozone folks.

Same thing.....it is on the top of the transaxle....under the big flex hose that goes to the throttle body.

First, you didn't mention the year of the vehicle, but I'll presume it's the typical AXOD(E) or AX4S transmission.

Your first post indicated that the transmisison acted normally when in any range but OD. That usually means that the trans is in manual mode and that the PWM solenoid which is used to control internal oil pressure is inactive. In a nutshell, that means the transmission is operating at higher line pressure (or nearly full) instead of a reduced pressure. That can force sticky valve spools, gummed or sticky clutch seals, and even worn clutch splines to act as they should rather than hang up or operate slowly.

The PCM modulates the line pressure when in OD (full automatic mode) to allow softer shifts and less transmisison strain. Raising the pressure can help overcome some internal mechanical problems.

Another method to test this is to clean off the TRS, disconnect the electrical connector (mainly to make sure it can be removed easily) then reconnect it. Start the engine, then disconnect the TRS connector again. This will operate the transmission in fully hydraulic mode and at higher line pressure. Drive the vehicle and see if the shifting is more normal, even though the MIL will be lit and OD light on the end of the shift lever will likely flash the whole time. If the shifting through all the ranges is firm and positive (no slipping) there may be a TRS problem or oil pressure problem. If the shifting is still abnormal or includes slippage, that can indicate further machanical damage to the transmission.

If the transmission seems to be relatively normal at higher line pressures (in manual mode), you may be able to improve the operation by draining old oil, changing the filter, and filling with clean, proper oil designed for the trans. As wiswind mentioned, the clean oil can help clear out accumulated deposits and improve sealing to help shifting conditions. The clean filter can only help oil flow, and provide correct pressure and cooling.

If the operation doesn't improve at full line pressure, I'd avoid changing oil until the trans can be diagnosed further. The extra friction material floating around in the oil may be the only thing providing any drive force in some ranges.

Hey, I wanted to thank everyone for there help. It turned out to be the Transmission Range Switch. Transmission shop replaced for $152.00. Thanks again!

I think I also paid $150 when I had mine done. So, I think you got a decent price. Glad to hear that it is fixed.