1995 GM Cadillac STS 4T80E trani 94 shift ratio A 76 force motor malfunction problems
 

I had buy a sts 95 few month ago with 70000 miles (112000km). I saw, when I went home with car that the shift was hard and I had changed the shift solenoide + filter + oil of transmission

http://7c.img.v4.skyrock.net/7cb/cad...16576104_1.jpg




Ihttp://7c.img.v4.skyrock.net/7cb/cad...16576686_1.jpg



The shift was always hard after, especially from N to D and from 1 to 2.
I had 2000 miles to do, and last week the Over-drive was out, and the transmission went at first gear only. Stop and start car, and now I drive with 3.
When I want go at fourth, the transmission get at first after few secondes. I think it's a safety mode.
Now I have buy a scanner and put it at car to check and appear this:

94 shift ratio A problem

It mean that I must chang the solenoide, but i have already to do this...

What can I check or chang? The speed sensor ? ECM? Other?

Ah, and my transmission didn't smell burn, and oil was on good condition before chang it, and filter was already chang before buy car.


I have this too at scanner:

76 force motor malfunction

But this, I don't understand.

You don't need scanner - scanner built into this car. See FAQ about On Board Diagnostics. For trans concerns it is limited, if you can get a Factory Service Manual, possibly from Quebec, Canada (it may be in french) it will help alot. When solenoid kit was installed were all parts installed? Bracket in kit keeps filter from blowing out eventually breaking solenoid; typically you will loose 4th gear first and shortly afterward lose the other gears.

The 76 force motor malfunction refers to the PCS(pressure control solenoid). This solenoid is in the side cover of the trans...not in the bottom, as the two shift solenoids that you replaced are. This code is most likely the cause of the harsh shifts, but any trans code will force the trans into a "limp home" mode, which raises the working pressure of the trans, in an attempt to keep it from burning itself up due to a malfunction.

The 94 shift ratio A problem does not mean the solenoid is bad, or needs to be changed again. It only means the PCM commanded a gear that did not take place, such as the 3rd-4th shift. This could be because of a defective solenoid, a stuck valve, a hydraulic problem(internal leak), or even a wiring harness problem.

The two filters you changed(in the picture) are "scavenger" filters. The main fluid filter is in the side cover of the transmission. Removing the side cover with the transmission in the car is almost impossible...it's actually easier to remove the trans for any service work in the side cover...:mad:

You should also check the transmission electrical connector for corrosion, and/or terminals that have pulled out of the connector. This is a fairly common problem.
I also heartily recommend the Factory Service Manual if you plan on doing any service work yourself...they Service Manuals are invaluable in helping troubleshoot all of the things that can/will go wrong.
hth

First, thanks for answer.http://7c.img.v4.skyrock.net/7cb/cad...16577278_1.jpg

You mean pressure control solenoid like at this picture ?



About Factory Service Manual I had bought this:

http://7c.img.v4.skyrock.net/7cb/cad...16592400_1.jpg

It's great book, but not so much information about transmission.. :(




Yes I have put the small filter + new bracket too with solenoid.

Yes, that is the PCS in the diagram. :D
The Haynes manual is ok, but they tend to cover too many year models to be very specific about anything.
I would suggest unplugging the transmission electrical connector, and checking for corrosion, or any wire damage. The connector is hard to get to, but it is in an area that gets a lot of heat, and moisture, as well as engine oil from cam covers leaking.
I could e-mail you the diagnostic routine for checking the PCS, as well as the wiring diagram for the trans/vehicle, if you need. :)

Oh yes, this would be great ! :)
My mail:
memez@mrachassis.com

Oh, and I will check all connection this week end, and prepair order at rock auto for PCS and some other things.

And something else: I had put DexronII (ATF 220) and may be it's not the right oil? Dexron III (technosynthèse) will work better?

After look at web this evening, I have understand exactly what you have meaned. In fact there are 2 valve body @ this transmission, one at bottom and the second on side...
Ok,ok I reading somewhere that it's possible to remove cover by only move in car the engine/transmission.
I will chek first wire I think..

Any Dextron fluid is fine...no need for any "special" fluid for the 4T80E. Dextron III is the most common fluid, so that will work. :)

Info is in the (e)mail to you. :D Just need a couple of minutes to get it uploaded....

I have disconnect this connector today, to clean it. It was full of transmission oil inside!
I had clean with airline, then dry it and connect. Put scanner, clear code, then drive, but problem stay always here... :(

http://7c.img.v4.skyrock.net/7cb/cad...10054242_1.jpg


I receive these following parts from rock auto:
-Main filter
- Pressure control solenoide
-TCC solenoide
-TFT sensor
Now, I look the best way to get out (under the car) my tranny to remove the side cap...

http://7c.img.v4.skyrock.net/7cb/cad...10055426_1.jpg

If you do try to remove the side cover, take notice of where the studded bolts are in the cover. They will need to go back in the same location. By "studded", I mean the bolts that have extended, threaded ends on them for brackets.
The solenoids are held to the valve body with clips, so no need to unbolt anything else(once the side cover is off).
Also, don't be surprised if the connector clips break when you disconnect them from the solenoids. They get brittle with age/heat cycles, and break easily. The connector will still function properly, tho.
The TFT sensor is plastic, and very easy to break. It is normally only finger tight in the valve body, so don't try to tighten it down with a wrench. :D
hth

Thanks for advice :)

I had chang the PCS, but problem still..
I didn't drive yet with car, too much snow outside.
But when I put transmission at D or R, very hard shift again!
I put scanner, and problem is always here : 76 force motor malfunction
I'm sad! :(

New PCS :

http://7c.img.v4.skyrock.net/7cb/cad...56587972_1.jpg

Ho-hisse !

http://7c.img.v4.skyrock.net/7cb/cad...56597706_1.jpg

The side cover :

http://7c.img.v4.skyrock.net/7cb/cad...56593520_1.jpg

More photos:
http://cadillac-sts.skyrock.com/8.html

Have you cleared the codes yet? If the code(s) is still in the PCM, it will still have issues. If the codes were cleared, and the problem is still there, that leaves either a problem in the harness/connectors, or the PCM. I have seen harness connectors with massive corrosion behind the little rubber "seal" that is down inside of the connector. You may want to pull that seal out, and have a look at the area behind it...

Oh, thanks for your quikly answer.

Yes I had cleared the code

Work of today :

- First I have disconnect again the 20way-connector, and check behind (inside the connector ==> OK
- Then check (with ohmmeter) the purple and blue wire (side of transmission) and found 6 ohms (must be resistance between 3 and 8 ohms) ==> OK
- Then check harness between 20/connector and the white connector of PCM ==> OK
- Then connect again the 20way-connector and put ohmeter between trans pressure control solenoid high and low terminals (white connector)of PCM harness (C15 & C16) and found 6 ohms ==> OK
Then put ohmmeter between terminal C15 & C16 and ground , nothing ==> OK

The result : I order one new PCM . . .

Today,I have put the new PCM at car.

First the good news:

76 force motor malfunction is disappear ! :D

Second, the bad news :

94 shift ratio A problem is back ! :(

+ 80 throttle position sensor - idle not learned after PROM reset

I have drive car a little before, transmission go on safety system at first gear.
I get mad with all these problem ! :mad:

What can I do now ?

Ah, and bord computer (when I start car) say me that I must chang the transmission oil ? But it's new !

Today, I checked both shift solenoid A & B . To do this, I have disconnected the connector of PCM harness and put E4 and E5 at ground, put key on, and listened under car, near valve body : both valve are OK, because I had listened it !
It mean :
- No problem of valve (They are new anyway)
- No problem of harness , from valve to PCM
- New PCM

What else ? :confused:

Internal leak of valve body ? :confused:

The new PCM will need to have the idle relearned. The service manual should have that procedure, if you have the manual. If not, I can e-mail the relearn procedure to you.

The shift ratio A code does not necessarily mean there is a shift solenoid problem. It only means that a shift was commanded, and the PCM did not see a change of ratio. This could be due to a faulty speed sensor/wiring, or even the wrong gear ratio of the transmission.
Do you know if the transmission has ever been out of the car, or possibly changed at some time?
Does the car not shift at all, it just stays in 1st gear?
A stuck shift valve could cause that, also, but the symptoms you are describing sound more like an incorrect ratio trans, or a faulty speed sensor signal to the PCM.

Well,
On order : (about code 94)
When I had buy car I had all speed at transmission.
After some thousands miles, suddenly, at freeway, the 4 speed disappear and the transmission went at 1.
Now the problem is like this (with all new parts)
- After clear code, and When I put transmission at 3 and drive car, evrything OK and no code 94 appear The car go at 1 to 2 and 2 to 3 without any kind of harsh shift.
But when I want put transmission at 4 and drive it, the car (when transmission go from 3 to 4) go suddenly at 1 and the code 94 appear.
The car was good at start, the this problem suddenly happen. It mean that something (who was good before) is broken or stuck or something else. But My question now is: What ? Because to chang parts on car, it's not problem,I must only now what I can chang ? when ,(and if) I have speed sensor problem, the PCM will appear one code about this, no ?
About code 80
Yes I'm interested about the procedure : memez@mrachassis.com

Outside Air temp more than 50*F(10*C), so the A/C compressor will engage.
Start engine and allow to idle until coolant temp is 176*F(80*C).
Idle for an additional 5 minutes.
With engine running, enter On Board diagnostics.
Turn engine Off. Wait 20 seconds, then turn ign. ON, with engine Off. Re-enter OB diagnostics, turn key Off, wait 20 seconds(again),turn ign ON.
Turn ign. Off. Wait 20 seconds, then start engine. Apply brakes, and place trans into Drive. Turn Climate Control to Off and allow engine to idle for one minute.
Turn Climate Control to "Auto" position and make sure the A/C compressor engages. Allow engine to idle for one minute. Place trans into Park, and turn ign. Off.
:D
btw...this procedure will NOT work if the A/C will not come on, so if your A/C doesn't work for some reason, the idle relearn will not happen.
On the 94 code, if all of the electrical stuff is good, and it appears that you have tested everything correctly, you have two possible problems.
Either the transmission is slipping in, or has no 4th gear, or you have the wrong ratio trans in the car.
When the trans shifts into 4th gear, does it "neutralize", like it's in neutral, or does it feel like it shifts, but slips?
The strategy for the TCM gets very specific in 4th gear, and it will not allow for any speed differences other than what it expects to see. This is why a speed sensor, an incorrect ratio, or slipping band(or clutches) can set this code.
I had a 93-94 model STS in the shop that had the exact same issue. Worked fine 1-2-3, but as soon as 4th gear was commanded, it set a ratio code, and shifted HARD. I fought with this thing for a week before I realized it may have the wrong ratio in it. As I found out, by checking the VIN on the trans, it had been swapped. I fixed this one by simply changing the differential("final drive") gears, which can be done with the trans in the car. Worked like a champ after that.
If your trans is NOT burnt up, I have to believe it is the incorrect ratio.:(

update:
I went back and re-read all of the posts. You say that originally, the transmission was working fine, and then the problems started after a few thousand miles. This tells me that the ratio is probably correct...which is good. The bad news is, the trans has probably burnt the band for overdrive.:(
The two shift solenoids are good, since it has 1st gear, so you can rule out a solenoid problem. There is a VERY small chance that a shift valve is stuck, but I've built probably 50+ 4T80Es, and I've maybe seen ONE that had stuck valves. More than likely, if one valve is stuck, there are others that will also be stuck, which would create more problems than you are having.

The last chance :
I have ordered the sensor VSS and shift solenoide again.
I will chang the one and the other, then try car...
But anyway, I remember fo this things:
The men who drived cadillac before me, had a big trailer. It's very possible that the band was very used when i bought cadillac.
http://www.compnine.com/largeimg/950504GM04-465.gif

Parts 523 : The best is the price of this band , only 6.90$ at rock-auto...
Anyway I have 2 possibility :
- Or buy an other transmission and swap
- Or I fix . . .
I had build some Fomoco C4 and C6 + power-glide at past. I'm not afraid to open transmission and by this way, we will see what's exactly happen in this putain of transmission ! :D

Be careful handling this trans. It weighs almost 300 pounds!:eek:
If you decide to pull it out, be sure to replace the seals in the channel plate for the input sprocket, as these are the #1 problem with this trans. Another problem is the forward clutches(#s 816 & 817 in your diagram). In every single 4T80E I have done, there has been at least one of the clutches with the friction material flaked off of it.
It would be advisable to get an overhaul kit, and just do the entire trans while it is out. Just replacing the band(if that's what it needs) isn't worth the trouble of pulling the trans out of the car, imo.
Also, depending on how bad the band is burned, it may have damaged the reverse clutch drum (# 500 in your diagram). I've seen many of those drums turn blue from the heat of the band slipping, which causes them to no longer be round.
The low/reverse band(# 13) also has issues with the friction lining flaking off, so inspect it carefully.
The rest of the trans is pretty solid, and we don't see many problems from any of the other parts, unless there has been some abuse, or major neglect.:D

You should be able to see part of the reverse drum with the lower pan off. You might be able to see if there is evidence of the band burning from there. There is an opening in the case there shift linkage is, and part of the drum is visible.
Another note....on the shift linkage wire that connects the case linkage to the valve body, there is a plastic clip that holds the wire to the case linkage...be VERY careful removing that wire linkage, as the plastic clip will break very easily.

80 throttle position sensor - idle not learned after PROM reset :

After 3 times that I had tryed the procedure, this code is disappear ! :D
10000000000 times thanks adam's apple ! ;)
And for the first time, since I have this cadillac, the MIL light is turn off :)

94 shift ratio A problem :

Today , I tryed this : tranny at 3 and drive car at 90 km/h (55 mph) on flat road,after I put 4 and didn't put gaz (thorttle full): the transmission go at 4 , everythings ok. Then put 3 again, the transmission go at 3. Then 4 again , and after few secondes , keep slowly gaz and suddenly, the rpm go out and the MIL turn on and transmission go at 1.
I think you have right (again) adam's apple, I have not any electric problem, but mechanical problem like the band....

A big work wait me !:eek:

Happy to help :), but sorry it isn't an easy fix for the trans :(.
Thanks for posting back what you found, though! We're here to help!;)

I boring to drive with 3 speed transmission . . . :D

http://7c.img.v4.skyrock.net/7cb/cad...71155408_1.jpg

http://cadillac-sts.skyrock.com/22.html


First remove all, then open tranmission, then we will see what order . . ;)

did you dig out the trench just for this job?




.

Oh no, i had doing some other job on it !

http://23.img.v4.skyrock.net/23f/mra...52387572_1.jpg

http://23.img.v4.skyrock.net/23f/mra...62779556_1.jpg

http://mrachassis.skyrock.com/50.html

Good luck with it, and let us know what you find!

No Fourth Gear - Could be Caused by the Fourth Servo
 

No fourth gear could be the fourth band, but your problem sounds like the fourth servo. Fixing the fourth servo is not a big job.:)

Check the fourth servo before the band, because it is easier to inspect and fix. There is an access cover on the side of the transmission case. See the attachment and look for:
Cracked 4th servo cover. (524)
Rolled, cut or damaged 4th servo cover seal (525) or piston seal (532).
Broken or seized 4th servo pin. (527)
Damaged 4th servo piston. (529)

Harsh shifts are caused by high line pressure. This was caused by the no fourth gear problem because the PCM increases the line pressure when there is another problem with the transmission in order to protect the transmission. Because the harsh shifts were not there after the PCM was cleared and while driving in D3 before using D4, the cause of the harsh shift problem was confirmed.

The transmission oil indicator must be reset when you change the PCM or transmission fluid, because it is just a variable timer. The timer moves at different rates depending upon the transmission oil temperature. With hot transmission oil the timer moves faster. Reset the timer using the on board driver info system.

Save your old PCM. I think it is fine and it will be useful to eliminate the PCM from the possible cause of other problems in the future. I hope you saved all of the other good parts that you replaced. It makes me sad to see all of the parts and effort that you have put into fixing your car without sucess.:(

I admire your tenacity and like your service trench - wish I had one like it.:D

http://7c.img.v4.skyrock.net/7cb/cad...73154488_1.jpg

http://7c.img.v4.skyrock.net/7cb/cad...73156090_1.jpg

Hey, great, with you and Adam's, I will fix the transmission with finger in the noise and closed eyes ! (French expression) :D ;)
You had a good idea, to check the servo.
Look by yourself, everything look OK. :cool:

It's save and on the box from the new . . . Like the rest, you have right, may be at future . . :)


I continue the job and hope it's outside of car for next saturday. (I work on it only evening after work)

Servo-seal-cover all look fine to me. Is the fluid as black as it appears to be in the pic?

No,no. It's was few black behind piston, the fluid of transmission smell OK, and not especially black "things" inside. I will see under cover when I will remove it.

Work of today : :D

http://7c.img.v4.skyrock.net/7cb/cad...74208488_1.jpg

http://7c.img.v4.skyrock.net/7cb/cad...74209824_1.jpg

http://7c.img.v4.skyrock.net/7cb/cad...74212032_1.jpg

http://7c.img.v4.skyrock.net/7cb/cad...74213248_1.jpg
http://7c.img.v4.skyrock.net/7cb/cad...74214236_1.jpg

http://7c.img.v4.skyrock.net/7cb/cad...74215302_1.jpg

More photos :

http://cadillac-sts.skyrock.com/25.html

http://7c.img.v4.skyrock.net/7cb/cad...75237328_1.jpg

http://7c.img.v4.skyrock.net/7cb/cad...75238256_1.jpg

http://7c.img.v4.skyrock.net/7cb/cad...75247740_1.jpg

http://7c.img.v4.skyrock.net/7cb/cad...75252358_1.jpg

What I found inside the bottom cover.... :(

http://7c.img.v4.skyrock.net/7cb/cad...75256674_1.jpg

I think, it's particule of band or disc or both . .

Thanks for the photos confirming the problem. Was the debris present when you changed the scavenger filters?

You probably already know, but just in case... In addition to the scavenger filters, the main filter is under the side cover.

Not so much.
:);)


http://7c.img.v4.skyrock.net/7cb/cad...75668704_1.jpg

Quote:

---

I went back and re-read all of the posts. You say that originally, the transmission was working fine, and then the problems started after a few thousand miles. This tells me that the ratio is probably correct...which is good. The bad news is, the trans has probably burnt the band for overdrive

---

Adam's apple : you are the best ! ;)

http://7c.img.v4.skyrock.net/7cb/cad...75690728_1.jpg

http://7c.img.v4.skyrock.net/7cb/cad...75692558_1.jpg

Now, to continue remove all from inside (if I must continue) It don't want go outside. I suppose that I must remove the rear cover ? To access at some clips ?

http://7c.img.v4.skyrock.net/7cb/cad...75696620_1.jpg

Rear cover :

http://7c.img.v4.skyrock.net/7cb/cad...75697582_1.jpg

I strongly suggest obtaining a Cadillac Seville Transmission, Transaxle & Transfer Case Unit Repair Manual for guidance. Also consider a transmission overhaul kit.

The rear cover is called a Transmission Case Extension. To remove it, first remove the speed sensor and ground wire, unbolt the cover, then there is a roller thrust bearing and scavenge tube.

The differential carrier is next. It is important to first rotate the manual shaft counterclockwise to place the transmission in park and prevent the differential from rotating. Then unbolt the differential carrier.

The final drive carrier is next. Push on the output shaft in order to expose the left side gear snap ring and remove the side gear and thrust washer. Remove the final drive carrier, thrust bearing, and sun gear. The final drive internal gear comes out with an internal snap ring. The output shaft come out the left side of the case.

Adams Apple was right on and he knows more about these transaxles than me. Hopefully he will come back to help you.