1995 GM Cadillac STS 4T80E trani 94 shift ratio A 76 force motor malfunction problems
#21
02-16-2010, 01:23 PM
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.
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.
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.
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.
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 !
Last edited by memez; 02-16-2010 at 01:27 PM.
#22
02-17-2010, 08:45 AM
Be careful handling this trans. It weighs almost 300 pounds!
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.
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.
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.
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.
Last edited by Adams' Apple; 02-17-2010 at 10:03 PM.
#23
02-27-2010, 07:54 PM
80 throttle position sensor - idle not learned after PROM reset :
After 3 times that I had tryed the procedure, this code is disappear !
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 !
After 3 times that I had tryed the procedure, this code is disappear !
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 !
#24
02-28-2010, 11:13 AM
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!
, but sorry it isn't an easy fix for the trans .Thanks for posting back what you found, though! We're here to help!
#25
05-29-2010, 02:09 PM
I boring to drive with 3 speed transmission . . .
http://cadillac-sts.skyrock.com/22.html
First remove all, then open tranmission, then we will see what order . .
http://cadillac-sts.skyrock.com/22.html
First remove all, then open tranmission, then we will see what order . .
#26
05-29-2010, 05:50 PM
I boring to drive with 3 speed transmission . . .
http://cadillac-sts.skyrock.com/22.html
First remove all, then open tranmission, then we will see what order . .
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?
.
#29
05-30-2010, 04:38 PM
No Fourth Gear - Could be Caused by the Fourth Servo
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 !
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)
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.
Last edited by 2001_Seville_SLS; 05-30-2010 at 04:40 PM.
#30
06-01-2010, 03:34 PM
Hey, great, with you and Adam's, I will fix the transmission with finger in the noise and closed eyes ! (French expression)
You had a good idea, to check the servo.
Look by yourself, everything look OK.
Save your old PCM
I continue the job and hope it's outside of car for next saturday. (I work on it only evening after work)
Last edited by memez; 06-01-2010 at 03:37 PM.