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Transaxle

Tiny
SHDTREMECH
  • MEMBER
  • 1996 SATURN SL2
  • 4 CYL
  • FWD
  • AUTOMATIC
  • 156 MILES
When the engine is cold or even if it has warmed up 10 minutes or so in the driveway when driving on the highway the transaxle will not shift into overdrive. However, when driving @ slower speeds 40mph and the engine heats up the transaxle will shift into overdrive. Its like if the engine and transaxle has time to heat soak the transaxle will shift into overdrive. But taking off from home to work on the highway the engine after a few miles heats up to operating temp, but never will shift into overdrive. Just recently installed a new thermostat, egr valve. I put card board in front of the radiator trying to get the engine to heat up a little hotter and it seems to make no difference. As I said if I have driven the car for a few miles and if I set @ a long red light it will shift into overdrive. Sometimes when it has shifted into overdrive when driving on the highway @ highway speeds and the engine seems to cool down slightly the transaxle will down shift all by itself. ? What do you think? 96 saturn sL2 156,000K
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Tuesday, January 25th, 2011 AT 3:16 AM

17 Replies

Tiny
SATURNTECH9
  • MECHANIC
  • 30,869 POSTS
So do you have any code's?Also do you get a delay in reverse?
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Tuesday, January 25th, 2011 AT 4:22 AM
Tiny
SHDTREMECH
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  • 9 POSTS
No codes and no delay in reverse. Recently had a egr valve code replaced the valve. No check engine light. Seems to be temp related.
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Tuesday, January 25th, 2011 AT 4:45 AM
Tiny
SATURNTECH9
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If it's not going into fourth gear sometimes it's has to be setting a code P0734 4th gear incorrect ratio. If the computer cannot go into that gear with slipping it set's a code for that gear. Have you had your code's checked recently?If not could you please do that for me. So far it sound's like a pressure issue or a leaking 4th gear piston.
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Tuesday, January 25th, 2011 AT 7:50 PM
Tiny
SHDTREMECH
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  • 9 POSTS
I had the codes checked a few days ago and there are none. Not sure what you mean by "it sounds like a pressure issue or a leaking 4th gear piston. When the engine heats up it will go into 4th gear, but only after I have sat and idled for a few minutes after the engine is up to operating temp. Thats why it seems temp related.
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Wednesday, January 26th, 2011 AT 1:22 AM
Tiny
SATURNTECH9
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When the fluid get's hot it get's thinner and if there is a internal leak it most likely show it's fault then or a low pressure issue same thing. What I mean by a pressure issue is that the pressure could be too low inside the transmission causing your problem. Also what I mean by a leaking 4th gear piston is the clutches for each gear have a clutch pack and the gear's get engaged by fluid pressure behind a clutch piston that force's the steel and fiber clutch plates together to engage that gear. SO when that piston leak's the gear won't engage properly. Could you have the code's double checked and get back to me?
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+1
Wednesday, January 26th, 2011 AT 2:00 AM
Tiny
SHDTREMECH
  • MEMBER
  • 9 POSTS
I'll have the codes checked again and post the results. The trany seems to work ok when the temp is up, but if the temp goes down it will shift automatically out of 4th gear. Could it be a bad coolant sensor giving the computer a low temp signal and the computer not allowing the trany to shift into 4th gear?
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Wednesday, January 26th, 2011 AT 4:00 AM
Tiny
SATURNTECH9
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A bad coolant temp sensor or bad transmission temp sensor won't cause the transmission not to shift into fourth gear. That is usually caused by a pressure, electrical, Or a internal failure in the transmission. Let me know what you find with the code's.
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Wednesday, January 26th, 2011 AT 4:59 PM
Tiny
SHDTREMECH
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Haven't had time to have the codes checked yet, but just for grins I covered the entire radiator surface so no air would pass through the radiator and after about 5 miles driving 60 mph the trany shifted into 4th gear. I noticed the temp gage was showing that the engine coolant temp was a little hotter than usual. Just what you would expect. Go figure. Just some history this happened once before and I changed the thermostat and it fixed the problem. I suppose I could have gotten a bad thermostat that I replaced recently Thinking of changing the thermostat again. Any thoughts. By the way the trany stayed in 4th gear all the way home today.
(10 miles).
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Thursday, January 27th, 2011 AT 3:27 AM
Tiny
SATURNTECH9
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That's crazy I have never seen a bad thermostat cause the transmission to not shift.I have had a couple of my own saturn S model saturn's and had bad thermostat causing the coolant temp to be too low and customers as well and no shifting issue's. If a bad thermostat caused that then the car would never shift when the car was cold even with a good thermostat. Get what i'm saying?Let me know what code's you have and we can go from there.
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Thursday, January 27th, 2011 AT 9:22 PM
Tiny
SHDTREMECH
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  • 9 POSTS
I had the car checked for codes and there were none that registared.
The cardboard continues to work when the coolant gage shows a little warmer than normal the trany shifts into 4th gear and stays there unless the engine coolant cools down then the trany down shifts uncommanded. When I have time I will check the thermostat to make sure it is working as designed. Just a note: the trany seems to work just fine when it shifts into 4th gear. ?
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Sunday, January 30th, 2011 AT 4:30 AM
Tiny
SATURNTECH9
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As soon as you start the car when it's cold it should shift into 4th gear regardless. So a bad thermostat idea just doesn't make sense one way or another. The thermostat doesn't effect the shifting of the car. Another thing that doesn't make sense is if it's not shifting into 4th gear and it's supposed to it should be setting a code P0734 4th gear ratio error. Most likely you have a pressure issue probably with a bad valve body causing too low of transmission pressure. If you had a transmission pressure gauge you could test the pressure at idle with the line pressure fuse in and with it removed.
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Monday, January 31st, 2011 AT 4:36 AM
Tiny
SHDTREMECH
  • MEMBER
  • 9 POSTS
You could be right. The winter storm makes it difficult now to work on the car. Next step might be take the car to the tranny shop to have it fixed. Still no codes. Don't have a tranny pressure gage to test the pressure @ idle. Any other ideas. Still haven't checked the thermostat. Seems to take forever for the engine to heat up. Whereas it used to heat up idl
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Wednesday, February 2nd, 2011 AT 4:13 AM
Tiny
SATURNTECH9
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If it's taking forever for the car to warm up that could be a bad thermostat. As far taking the car to a transmission shop be warned most will tell you they have to replace the transmission or rebuild it. Even though most of the time it's a in car repair. You buy a transmission gauge set for less then they will charge you to diagnose the car. Unless your not good at fixing car's then your at the mercy of the transmission shop good luck with that one.
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Wednesday, February 2nd, 2011 AT 4:21 AM
Tiny
SHDTREMECH
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I am happy to report that I changed the coolant sensor and everything is working as before. The tranny shifts into 4th gear, the engine idles better and starts better. Was thinking I might have to change the fuel pump, but don't think I am going to have to do that. I fortunately was right it was a temp related problem. The $10 coolant sensor seems to be related to a lot of systems on the car engine and was an easy inexpensive fix. Thanks for replying saturntech9
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Sunday, February 6th, 2011 AT 8:10 PM
Tiny
SATURNTECH9
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Your right it is related to a lot of system's I have seen coolant temp sensor's reading over 40 degree's off of actual temp and never seen it effected the transmission shifting. That's the first I have ever seen of that. So the car never boiled over the coolant cap?Because when the coolant temp sensor's go bad they always read colder then actual temperature. Also the sensor run's the temp gauge and the computer temperature so when they go bad you never see the car overheating from the bad sensor.I have seen bad or ambient temp sensor's input's cause shifting issue's on those car's. Glad to hear you got it figured out though.
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Sunday, February 6th, 2011 AT 8:49 PM
Tiny
SHDTREMECH
  • MEMBER
  • 9 POSTS
It did boil over when I had the cardboard in front of the radiator and the weather was in the 70s a couple of days. Obviously I took the card board out and the gage reads just under the middle line on the gage after the sensor chg, whereas before it would never reach the first line on the gage unless I sat for a while and also had the cardboard in. But while it was cold it never boiled over and yes you are right the sensor seemed to be giving cooler signals than normal. Thx again
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Sunday, February 6th, 2011 AT 10:10 PM
Tiny
SATURNTECH9
  • MECHANIC
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Your welcome that's what were here for.
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Monday, February 7th, 2011 AT 12:44 AM

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