2000 Pontiac Montana O2 sensor failing and tranny slipping

Tiny
JJTEDDY
  • MEMBER
  • 2000 PONTIAC MONTANA
Transmission problem
2000 Pontiac Montana 6 cyl Front Wheel Drive Automatic 177k miles

When O2 sensor fails, does it affect on transmission? I noticed with my 2000 montana that since the O2 sensor failed a few months ago, the shifting on my transmission is slipping after 2o mins drive or when the engine starts to heat. Shifting is ok at the start or when I left home but after 15-20 mins drive I can feel that tranny is slipping every shifting of gears.I'm a bit hesitant to send it to mechanic to fix or change the o2 sensor because it might be useless if the tranny will fail or damaged already. If it is, is the additives like lucas transmission fix helps?Some say it's effective but most says it's not. Thanks
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Sunday, November 15th, 2009 AT 3:11 AM

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Tiny
KNOWYOURAUTO
  • MEMBER
Every vehicle issue that has multiple problems always begins with two steps. Fix the engine then the transmission. Engine running problems will often interfere with transmission shift points and feel, so they are always corrected first. This is the technical answer.

In my expert opinion unless you are experiencing a stalling, cutting out or major symptom, that the 02 sensors are not dramatically causing the transmission problems you are experiencing. If the shifts you are feeling are like delays between gears going up and down then you very likely have an internal problem; leaking clutch packs, sticking valve body, solenoid, etc.

To the question of aftermarket additives. They are not recommended professionally because their viscosity (thickness of flow) does not meet the standards required for the vehicle. That is the technical answer. I have had a handful of cars respond to the lucas transmission treatment for conditions like yours. It doesn't not work for hard or no shifts.

Good luck.
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Wednesday, November 18th, 2009 AT 6:32 PM
Tiny
JJTEDDY
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First of all, thank you for the reply. Well actually, I just noticed a little vibration on shifting after 15-20 mins drive or if the engine's already hot. But there are times that it doesnt vibrate or slip. If my tranny's already failing, does the computer reads it? When check engine sign turns on and when I scan it or use the code reader, it will only show code for failing o2 sensor.I hope it's just a minor tranny problem or 1st stage which can still be fixed. Does it help if I change o2 sensor and flushed the tranny oil? Thank you
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Thursday, November 19th, 2009 AT 11:30 PM
Tiny
DANAUTHIER
  • EXPERT
How much history do you have on the vehicle? Have you owned it since new and if not do you know the maintenence history?
At 177k on the odometer, if the transmission has not been serviced regulary I would not recommend the flush, a traditional filter change may be better. At that high of mileage without regular service, flushing will most likely not help your problem, it will just let you know how bad the trans really is. The trans has clutch plates with and abraisive material bonded to them, this allows the plates to "stick" together to carry the torque through to the wheels. As the plates wear the abraisive materials become suspended in the fluid, when you flush the old fluid out the abraisive materials go away too and the trans slips worse.
That being said, the vibration after it's warm leads me to believe it is the transmission not the oxygen sensor. Your vehicle should go into closed loop much faster than 15 to 20 minutes of driving.
This body style has a history of shift soleniod fairure, but that should leave a code. You stated that it only shows on O2 code, Which one is it?
I agree with Knowyourauto's opinion, engine problems will effect trans performance and the oxygen sensor is most likely not your the major fault.
All that being said, let me know what the codes have been and we will try to help you diagnose this.
Dan
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Friday, November 20th, 2009 AT 12:11 AM
Tiny
KNOWYOURAUTO
  • MEMBER
Jjteddy,
Danauthier has summed it up nicely so all I have are one comment and some additional follow up questions. I found your previous post about the Montana that says you owned the van since 173,000 miles, which would mean that the history is probably sketchy. I would concur with NOT flushing the transmission and recommend not servicing the transmission in any way for the same reasons already stated.

1) What speeds are the vibrations and what gears does it seem to affect?
2) Would you also describe the vibrations between gears as a shudder, similar to going over those rumble strips on freeway exit ramps, only less severe?


http://www.2carpros.com/forum/automotive_pictures/435113_bumps_1.jpg



3)Sorry to be redundant, but the slip...this is when the transmission either drops out of gear and the engine revs slightly, or when the trans shifts gears it takes more than one full second. Is this what you are experiencing?

Looking forward to hearing back.

Regards,
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Friday, November 20th, 2009 AT 2:21 AM
Tiny
JJTEDDY
  • MEMBER
Thanks guys! Before I went to work today I borrowed my friend's code reader. The code that I got was P1401- (EGR Valve stuck open or circuit performance). Honestly, I have no idea what are these or maybe it involves with emissions or something. Don't have any knowledge about the history of this vehicle actually since I bought this on a used car sales dealership 5 months ago. Actually it was 173km. Also, I might chose a wrong word. It wasn't actually totally vibrating maybe a little like your tire hit a small rock on the road every changing of gears. But whenever it shifts gear starting from 2nd, you can feel a very little sound from shifting and like it slip or missed 1 gear from tranny when it shift to next one. Usually after 15-20 mins drive. But other than that it runs ok. Thanks so much again.
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Saturday, November 21st, 2009 AT 2:24 AM
Tiny
KNOWYOURAUTO
  • MEMBER
Regarding your EGR code situation, this only interferes with engine at an idle in the way of running rough or stalling but goes away as soon as the gas pedal is pushed.

The symptoms of your transmission problem are pointed to the stator part of your torque converter. It commonly seems more like a sound between gears than the engine revving or flaring.

Both of these require looking at the data/information screen on a vehicle scanner and comparing the actual values to what the expected values are. Both are also on the expensive side of repairs. EGR valve replacement is around $300 and a torque converter is much higher around $700 or more.

If you can get access to a full automotive scantool, I can tell you the speeds and values to monitor so we can figure this out. But it takes some practice using them and the freeze frame operations, so it may require you to have a full diagnostic done. In which case check online for a reputable shop that specializes in transmissions and engine diagnostics.

Please post back if you would like additional information or find a solution to the problem.

Good luck.
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Saturday, November 21st, 2009 AT 1:07 PM
Tiny
JJTEDDY
  • MEMBER
Thank you so much! I really appreciate this.
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Saturday, November 21st, 2009 AT 1:39 PM

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