Update on my VSS Replacement

[Larry Bialecki]

Well I see no difference in ATX operation following replacement of the VSS. My 93 with 164 K
on it still shows problems down shiffting from 3 to 2, especially when warm and I now get a 647
code once in a while. I do not feel any slipping. Does anyone have any other suggestions
short of pulling the tranny? I have changed and checked the fluid.

Also, I occasional get the 181 and 189 codes. I know what the book saids for error,
but what is the most likely cause? What sensor needs to be changed or port need to be cleaned?
Is there any relationship between these two codes and the 647 code? I get the three codes
together sometimes.

 

[sdpatt]

181 (M) Fuel system was lean at part throttle Single, Right or Rear HO2S
189 (M) Fuel system was lean at part throttle - Left or Front HO2S
647 (M) Transmission 3rd gear failure

Since both O2 sensors are showing a lean mixture at part throttle, this is probably a real condition rather than a misreading pair of O2 sensors. It could be due to several conditions. One would be a vacuum leak in the throttle body or IAC valve area of the intake. There could also be a vacuum leak in the hoses from the intake to teh vacuum distribution header.

This may also be a cause of the shifting problems that are triggered by parameters including the intake vacuum. I don't believe a leak at the intake-to-head gaskets would affect both banks, but there could be a way to install the intake and create this situation. Whatever the source, your engine is running lean in the high vacuum zone of part throttle operation.

Another possibility is dirty mass air flow sensor filaments or an improper calibration of the EEC (LPM?) to the MAF flow characteristics. Have you changed any of the components mentioned so far? Any other sensor output errors would cause a code of their own.

I am not familiar with the causes of the 647 code.

 

[Mr Anonymous]

It's too bad you didn't know about that 647 code before spending all that time on the VSS.

The 'official' Ford PC/ED description for a 647 is "Incorrect gear ratio obtained for third gear."

Here's what Ford says can cause it:

Intermittent harness continuity.
Damaged Transmission Range (TR) Sensor.
Damaged shift solenoid.
Worn friction elements.

I'm betting one of the last two. Did you check the fluid in the pan and around the magnet for any debris? (If it was one of the first two, you would have most likely received add'l codes.)

In any case, I'm sorry to say that you're probably looking at a rebuild. frown

 

[Larry Bialecki]

Well replacing the VSS was a learning experience and looking back on it, it was worth it. Now I know how to drop a "Y" pipe with a lift. The VSS only cost $15 from Auto Zone and I did not break anything in the process.

I have looked at the contents in the pan and did not see any gunk. I guess I probably have a bad solenoid. I asked this several weeks ago and got a no answer, but, I will try again. Can the solenoids be checked/replaced without taking out the tranny? If I got the skill to replace the VSS can I get at the solenoids? I believe they are located under the tranny side cover drivers side. Would it be worth trying to change them out before I commit to a total rebuild? How much would they cost?

 

[Mike Kopstain]

Two times, my Dad's Windstar has eaten a range sensor. I'm not even sure what it does, besides telling the tranny what position the shifter is in, but it made a difference. It's only $25.00 and probably worth the swap. This swap takes 20 minutes, easier than the VSS. frown

 

[SVTTroy]

Larry Bialecki:
Can the solenoids be checked/replaced without taking out the tranny? If I got the skill to replace the VSS can I get at the solenoids? I believe they are located under the tranny side cover drivers side. Would it be worth trying to change them out before I commit to a total rebuild? How much would they cost?

Larry I am experiencing a similar issue as yourself. I have a harsh engagement on a 3-2 downshift. I would recommend checking the #3 solenoid before going in for a rebuild. There are a couple of things you can do without removing the trans. You can check the solenoid for an open, short to ground, or short to battery. I don't have the pin out handy but there is a white connector going into your trans right under the throttle body. This is the connection to the three shift solenoids. Replacing them doesn't require removing the transmission, but it does require removing the side pan covering the valve body. Certainly not an easy task, but a shift solenoid is less than 30 bucks. I my case the shift solenoid turned out to be electronically ok which, by my best guess, means either the solenoid is not mechanically functioning or the portion of the valve body that it controls has an issue. I just haven't has the time to investigate further.

 

[Larry Bialecki]

Well I guess its time to try the shift solinoides. It looks like I have to take out the driver side engine support and motor mount to get to the solinoides which are behind the tranny side cover. Has anyone done this before? Where can I get the solinoides? Are they part of the "shift kit"? Ihave the shop manual and it looks like if I am carfull I can change out the solinoides without taking out the tranny. Insight from anyone on this procedure will be appriciated.

 

[SVTTroy]

You've got the procedure right for accessing them. The can be reached by supporting the engine, removing the trans support, and taking off the cover. But you should first check them electronically first before all of that work. You could potentially change a good solenoid and still have a stuck or damaged valve in the valve body. Solenoid #3 controls mainly shifting into OD, but it also controls parts of the valve body like the 3-2 timing valve. If there is something obvious like an open in the #3 circuit, then it is an easy decision to replace the solenoid. You can get shift solenoids at any Ford dealer.

 

[Mr Anonymous]

With the support bar & tranny mount removed, you should just be able to get the valve body cover off. You would be dealing with pretty tight quarters working around the spindle, strut, etc. to get in there. One big concern would be doing all that work and getting everything put back together without getting any dirt & debris in the tranny.

I realize all too well what a tranny rebuild can set you back, but I've always been skeptical of randomly replacing parts on a 'guess' that with some luck the problem might be fixed. It seems more logical to follow the diagnostic steps & routines in the Helms manual to isolate and identify the problem.

Personally, I'd recommend spending your money having someone with a Rotunda tranny tester test the electronics in the tranny. I don't have the labor guide handy, but it shouldn't run more than an hour or two's worth of labor, and will rule in/out whether you're looking at an electronics or mechanical problem.

With the mileage you have on that tranny (you didn't mention if it's ever been rebuilt), you're just throwing good money after bad to replace solenoid(s) that aren't throwing any codes, IMHO.

If you are determined to try replacing one of the shift solenoids, you might as well replace all three along with the lock-up and EPC solenoids while you're in there. The 3-2 downshift pulls SS-3 low, and SS-1 & SS-2 high when OD is on, but with OD off SS-3 stays low in 3rd. The shift solenoids list out at about $31 from Ford, or about $25 for the ATP version at an auto parts store. The EPC runs about $50. Figure on 4-6 hours work start to finish.

In any case, please let us know how things work out!

 

[Larry Bialecki]

SHOooo

Thanks for the advice. I am not sure what I am going to do. I most likely will have the tranny rebuild but when there is a total failure. Till then I very much enjoy trying to figure out what is wrong. The tranny problem has been with me for about 9 months. Started by noticing that the down shift from 3-2 was slow. Now when the tranny is hot the down shift is really slow with jarring into 2nd almost at stop. I do not run the car hard (I do not drive the way I did when I was 20) and will nurse it along until I think I may be doing real damage. I really like the car and probably will keep it forever. (I still have the 72 Buick my wife and I bought 30 years ago and theTR-4A I used going back and forth to college).

I installed LEDs across the solenoids last night and now can tell when the computer commands shift change. I will be comparing the command signal to the actual performance to determine if the computer is performing properly or if the mechanical parts are acting up.

Have you ever heard of a case where the solenoids stick? They are the only thing I think I can change. They are OK electrically (23 ohms). Could they be sticking and not controlling the valves correctly? If the computer is scheduling shifting correctly (that means all the sensors to the computer are ok) then all that is left are the mechanical parts in the tranny. These are the solenoids, valves, pump, and friction parts. I do not feel the tranny slipping (high RPM increase before engagement). I think I have some solenoid/valve problem. Too bad I cannot change out the valves without removing the tranny. I just hate spending money for something I can do myself. Well things are cooling off here in CA and I expect the tranny will be working better being cooler.

Well I will keep the forum informed on what happens. Thanks.

 

[Larry Bialecki]

I placed LEDs across the three shift solenoids and watched them during running. Initially, when the transmission is cool I see no problems with my 3-2 down shift. When the transmission is hot I have the problem. When in 3rd with a request for additional torque to the wheels (request for downshift by depressing the throttle during goring around a turn or climbing a hill) the downshift problem occurs. The shifting is slow with I believe a period where I am in neither 2nd or 3rd gear. After about 2 seconds it goes to 2nd gear with a shutter. After this occurs I no longer have a 3rd gear during normal driving with the 2nd to 4th shift at about 35 MPH. On deceleration the 4th to 2nd occurs at about 30 MPH with a shutter. My LEDs never show the computer trying to energize the 3rd gear solenoid. At this time the 3rd solenoid is reading correctly resistance wise. If I stop the engine and restart all is back to normal until I again request addition torque in 3rd gear. During the problem I get the 647 code. After stopping the engine I can clear the code and it does not show again until I again get the problem downshift.

Questions:
Does the computer change shifting schedule based on a failure code occurrence and if so does this clear by turning the car off and on? I do not understand why I do not see the same light configuration for 3rd after the problem occurs.

Is there a sensor on the transmission that detects the desire for additional torque which may be failing under hot conditions? The transmission speed sensor?

If a solenoid or valve was stuck in the transmission valve body would not the computer still try to command 3rd?

Again, I have changed the VSS, have no gunk in the transmission pan, feel no slipping during normal operation, and the transmission fluid dose not smell burnt.

 

[Larry Bialecki]

Results of my testing with the LEDs across the solenoides show proper operation for normal conditions. However, when I have the down shift problem, 3 - 2, the LEDs go from S3 on (3rd) to S1, S2, S3 on for about 1 sec, than to S2 and S1 on (2nd). During the S1,S2,S3 time is when I feel the 3-2 problem.

I could not find any sequence in the book where all three are lit at the same time. Does anyone know is the "three lit" sitiuation is normal? If not what might be causing it? Does anyone have any comments on my previous questions in the posting just above this?

 

[SVTTroy]

I found this article. If what they say in it is true then it looks like "three lights" is normal for a couple of seconds between shifts. Maybe the response time of the solenoid is lagging or sticking and causing the issue? BTW it also states this event won't show up on any shift solenoid schedules.

Article

<small>[ September 20, 2002, 02:27 PM: Message edited by: SVTTroy ]</small>

 

[Larry Bialecki]

Wow Svttroy

Thats quite an article. Gives me a lot to chew on. I am getting more and more sure that I have a valve body problem rather than a friction part problem. For me thats good because I do not want to pay to have the tranny pulled. I can get to the valve body.

I will keep all informed.

 

[Larry Bialecki]

Update: Better description of my transmission problem. The problem is in the kickdown downshift from 3 to 2. Coastdown downshift works fine all the time until I have the kickdown failure. Coastdown worked from 3 to 2 below approximately 10 mpg. The kickdown gives problems when hot when trying to accelerate out of a turn or up a hill. When in 3rd (Solenoid 3 on) and trying to accelerate all three solenoids will go on, the car will shutter and than go to 2nd ( Solenoids 1 and 2 on). After this happens, 3rd is no longer available (commanded) and I get the 647 error. The shifting schedule is than 4th to 2nd at 25 mph with harsh engagement. If I turn off the car and start again, 3rd is back and all is find until I again try for kickdown from 3rd. To prevent the 3rd kickdown problem I am careful with attempting acceleration in 3rd when hot. To the point of manually going down to 2nd into the curve or riding 2nd up hills. Max sustained RPM in 2nd of about 3500 or about 40 mph. I still think I have a valve body/solenoid problem and not a transmission friction part problem. Next step is to flush out the transmission good to see if I can resolve the problem. If not, pull the valve body and inspect/replace solenoids.

Does anyone know if the computer changes its shift schedule following a 3rd speed problem detection (error 647)? Svttroy do you have any more of the "Gear" articles? The one you posted was very interesting.

 

[Mike Spataro]

Hi Larry,
I have been following your post for some time and have the identical problem on my 93 ATX with a 140K. The drive train was transplanted in a Sable wagon in 1994 with 5K on the engine and transmisson. My down shift problem started about 75K and I did a fliud and filter change and the results were the same; a hard downshift from third to second. I am sure there are many of us that have the exaxt same problem. Thanks for sharing the play by play information. Mike

 

[SolidState]

I ahve similar problems too with my bum tranny.

In the manual I have on CD, it states the following for SHIFT CONCERNS 3-2 Auto:

Electrical:
Elec Inputs/Outputs
Wiring Harness
Shift Solenoids
PCM
MLP Sensor

Hydraulic/Mechanical:
Improper pressure:
Direct Clutch
Forward Clutch
EPC pressure
Line pressure

and the list goes on. IF you want me to email it to you, lemme know.

Now, to swap my VSS.... squint

Teg