Mechanics

LS2 AUTO TRANS SLIPPING WHEN WARM

2000 Saturn Other • 6 cylinder FWD Automatic • 81,000 miles

2000 Saturn LS2 3.0L Auto 81K
Trans slips after reaching operating temp. Fluid level/type/condition all good. Fluid/filter change had no effect. No friction material or metal shavings in pan. Tech replaced press. Valve solenoids ($1135) with no effect. Tech now says "trans controller" ($500) is at fault. Any suggestions/advice? Thanks!
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Matso
January 25, 2011.




So when you say transmission controller do you mean the transmission computer?Also I think I would get a second option after he replaced the transmission line pressure control solenoid for a slipping transmission and that didn't fix it. SO is he willing to make the 1135 right he charged you to fix it and it didn't fix it?Also all the case's I have seen with a bad pressure control solenoid have been for a hard shifting concern not slippage. Has he even performed a transmission line pressure test or a step pressure test?You could have a faulty valve body or a bad pump in the transmission. Do you have a trouble code's in the computer?What make's him think you have a bad transmission computer if that's what he is saying?


Saturntech9
Jan 25, 2011.
Trans ECU, apparently, yes. He claims it isn't processing the speed signal which is causing erratic/delayed shifts.
I have had hard shift/"wrench" service light issues for several years. I mentioned this to the tech and thought I made it clear I wasn't concerned about it, since it's a minor annoyance. The symptom I described in detail (engine revving as if the tires are 'roasting', but vehicle not accelerating) is the issue I wanted resolved (or so I believed I had communicated to him).

I just returned the car to him/test drove it with him to demonstrate the symptom. As is usually the case, a different symptom presented itself, on the test drive, rather than the expected one. The engine suddenly had no power, but the trans stayed engaged (reminiscent of when the MAS failed two years ago). I popped the hood, disconnected the MAS, and drove again. The "no power" condition was gone, and the original 'slipping trans' symptom was immediately obvious. He STILL wants to replace the ECU. My wife insisted that I stop payment on the $1135 check, which I did. He now has my car, but none of my money. Not sure what to do at this point.


Tiny
Matso
Jan 25, 2011.
You asked about pressure tests: Yes, the pressure is good throughout the range of trans operation (on hoist/no load). He claimed to have found/repaired a 'sticking valve' (not sure if he was talking about a shift valve in the body, or something else). The one OBD fault code he mentioned was "wrong 4th gear ratio". (No clue what that indicates).


Tiny
Matso
Jan 25, 2011.
So the transmission computer isn't getting the speed signal or the turbine speed signal aka input shaft speed?Or is it getting it and he just thinks it's not doing anything with it?I have seen a few of those computer's fail but usually the one's I have seen that people thought were bad was just a pressure issue valve body issue or a bad seal in the transmission. When I asked about the pressure I wasn't talking about the wheel spinning on the rack.I was asking if he actual hooked up a transmission pressure gauge and performed a pressure test on the fluid pressure in the transmission and the control of it?Here is the code description for the no 4th gear code P0734. Also below that is the pressure test I was asking about and i'm posting the pressure chart for it. For the no fourth gear code that could be pressure issue electrical issue seal failure etc.
The Transmission Control Module (TCM) calculates gear ratio based on the transaxle input and output speeds. The TCM compares the known gear ratio to the calculated ratio for the selected range. When the TCM detects an unknown gear ratio when 4th gear is commanded, then the DTC P0734 sets. DTC P0734 is a type C DTC.

DTC PARAMETERS

* Engine is running
* TPS greater than 8%
* Trans fluid temperature between 21 C (70 F) and 130 C (266 F)
* Engine torque greater than 2 ft-lbs
* Commanded ratio = 1st gear
* No TPS, TFP, VSS, ISS codes
* No engine torque default
* Time since last manual range change greater than 6 seconds
* TFP not in PARK or NEUTRAL
* Vehicle speed greater than 5 km/h (3 mph )

DIAGNOSTIC AIDS

* Check for improper transaxle operation per the chart.
* Check for an incorrect calibration.


Saturntech9
Jan 25, 2011.
The latter: TCM not processing the input shaft speed signal.
His comment that "pressures were right where they were supposed to be" suggests that he did, in fact, connect a pressure gauge and compared readings to specifications.

Someone suggested the overrunning clutch on the forward hub is probably not holding. For a sprag clutch failure, I would expect to find steel 'dust' all over the pan magnet. There was no metallic debris of any sort in the pan, and minimal (typical) friction material dust. (Sounds like you know 'what time it is', more so than the tech who has my car. Thanks for your time with this issue).


Tiny
Matso
Jan 25, 2011.
As far as the pressure test goes as you can see on the pressure chart you have to command the line pressure solenoid with different amperage's thru the transmission computer that requires a tech 2 scan tool with the correct saturn software most shop's don't have to correctly do that test. They can do a basic pressure test but one to test it correctly most cannot. The first thing I would be sure of is that a proper pressure test was performed because if they rule out the pressure and it wasn't done properly. There going to be going after your computer or want to replace the transmission or take it apart. Would be terrible to do that if it was just a pressure issue.I would take it to a different shop and pass on the info I have provided. Good luck and keep me in the loop of what is going on with your transmission.
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Saturntech9
Jan 26, 2011.

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