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Just bought 2012 gmc acadia with117k on it. Mint cobdition cosmetically and seemed to drive fine untill yesterday. It seems when im doing about 40 mph or 60 mph the rpms drop betweem 1700 and 2100 and i get the shudder/buck. If i let of gas or accelerate it powers through but when in steady speeds in traffic it gives those issues. Let me know what you think? Ive read several posts here that start with a lot of minor work and end withtorque converter. Hope this isnt the case.
 

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:welcome: to the forum.

Best bet would be taking the car to a transmission specialist and let them diagnose the problem in real time. Good luck.
 

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To the OP, let me know what you learn. Mine does a similar thing under load.
 

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My 2011 does something very similar, but at a lower speed. 140k miles on it. Waiting to take it to a transmission guy.

No lights on the dash, no codes on the computer. The only thing it does is take a little over a second to shift from 3rd to 4th gear.
 

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recently also began to notice delayed shifts.
mine was when I shifted to D. It took up to 3 seconds to engage.
I scanned. No codes.
Every now and then on sudden stops, once I had stopped, it felt like a car bumped me from the rear.
I took it as a delayed shift from 2 to 1 when the stops were sudden.


Based on other posts on delayed shifts, I ordered the parts and spent a saturday to replace them. Little plastic discs ($34) that wear and tear.
$107 total with trans fluid and seals.


But, never did get CEL from trans.


The transmission now engages D, in a fraction of a second. No more feelings of being bumped in the rear.


I recommend you read through this entire thread to see what others post on what symptoms they felt...
see if anything matches with yours.


https://www.acadiaforum.net/24-engine-drivetrain/13888-how-replace-tehcm-tcm-transmission-module-p0752.html
 

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I've noticed something new in my 2009 (just turned 61,000 miles). When on the highway on cruise (65 - 70 mph) in 6th gear, as I begin a slight incline, the car will make a momentary minor "jerk" and I can see the needle of the Tachometer twitch just a bit. If I don't address it - it'll continue - and sometimes it'll downshift on its own.

This never happened before, but is fairly routine now. Mind you I'm not towing, the car is essentially empty, no apparent head wind.

I've begun to drive on longer highway trips in "manual" mode in "6", and as I approach an incline that I suspect will induce this twitch - I manually down-shift to 5th - and no more issue. Perhaps a component has begun to wear after 60,000 miles... but I never had this issue in the previous 9+ yrs.
 

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I've noticed something new in my 2009 (just turned 61,000 miles). When on the highway on cruise (65 - 70 mph) in 6th gear, as I begin a slight incline, the car will make a momentary minor "jerk" and I can see the needle of the Tachometer twitch just a bit. If I don't address it - it'll continue - and sometimes it'll downshift on its own.

This never happened before, but is fairly routine now. Mind you I'm not towing, the car is essentially empty, no apparent head wind.

I've begun to drive on longer highway trips in "manual" mode in "6", and as I approach an incline that I suspect will induce this twitch - I manually down-shift to 5th - and no more issue. Perhaps a component has begun to wear after 60,000 miles... but I never had this issue in the previous 9+ yrs.



this sounds more like the issues that many 2009s have.
Many owners report what they think is the trans slipping.
Usually when cruising along in 6th, and they begin to go up a hill/incline.
They think its slipping.


I think the majority of the time, its turned out to be misfires.
The 09s are known to have issues with the coils/plugs.
 

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Can you share more details (part #'s, etc.) about the little plastic discs and seals?
Sonnax Pressure Switch Installation Tool Kit - 124740-TL30
ACDelco Trans Cover Gasket - 24229593
ACDelco Wiring gasket - 24240184

Follow links in this thread for other information.
 

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Lubegard 19610 Dr. Tranny Instant Shudder Fixx, 2 oz.
recommended by a trusted mechanic. Eliminated shudder on my 2012 SLT in about 500 miles but had noticeable improvement right away. It's about $8 at Amazon
 

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Yea, I've also thought that it could be some mis-firing or a performance issue. I think it may be tough to diagnose w/o running up the road w/ a black-box attached. I've got 61,000 miles, and two years ago needed to replace the coil on cylinder #1.
 

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Would not a coil mis-fire throw a CEL code? Particularly if it occurred more than once?
 

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Just bought 2012 gmc acadia with117k on it. Mint cobdition cosmetically and seemed to drive fine untill yesterday. It seems when im doing about 40 mph or 60 mph the rpms drop betweem 1700 and 2100 and i get the shudder/buck. If i let of gas or accelerate it powers through but when in steady speeds in traffic it gives those issues. Let me know what you think? Ive read several posts here that start with a lot of minor work and end withtorque converter. Hope this isnt the case.
First, I am not a mechanic. My car is a 2012 (purchased in late 2012) with about 107K miles. In great condition cosmetically but with some "old age issues'. I noticed the shuddering, jerking, skipping, quick hesitation at about 106k, about 1-2 months ago. It happens going up small inclines, on flat roads, highways... at any speed and Usually once in the AM and maybe PM. In late December, I needed to change the SPark Plugs and the Water pump ( I had an ongoing leak for about 2 months). My next fix, part of the "annual physical on my car" would be a transmission flush just due to the miles. My aim is to be preventative and plan out potential cost. But I called a mechanic today to find out about the "shuddering" and his 1st thought was transmission. We schedule an appt for Friday with a stop at transmission person. On my way home tonight, the shuddering/hesitation feeling happened many times. My car felt a bit sluggish also. I have no warning light. On some occasions (2-3 times a month), there is a burning smell which I have smelled for years and the dealer could not ID the problem. If it happens to be a transmission issue, would a transmission flush fix the problem. New transmission is definitely not part of my plan. Thoughts?
 

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My 2012 does the same thing with 122k and it started at 107k. I purchased it used and was able to get the maintenance records from the original owner's dealer; outstanding records too.

Through my research in this great forum and others I believe the torque converter to be the culprit. The transmission has been flushed at least twice and an additive was used offering only a temporary fix.

One thing I've found that helps a lot is to inflate your tires to at least 38 or 39 psi. I think the lower rolling resistance helps and the shudder is practically gone... at least for now.
 

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My 2008 does this exact same thing. I got my computer scanned and it said P0989 "Transmission fluid pressure switch 5 circuit low voltage." Any ideas how to fix?
 

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My 2008 does this exact same thing. I got my computer scanned and it said P0989 "Transmission fluid pressure switch 5 circuit low voltage." Any ideas how to fix?
Start by checking the transmission fluid level/condition and clear the code. If it's good and the code persists, the problem is deeper. This article should give you some idea of what possible repairs are necessary: https://www.autoblog.com/2016/09/14/p0989-obd-ii-trouble-code-transmission-fluid-pressure-sensor-sw/
 

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Just bought 2012 gmc acadia with117k on it. Mint cobdition cosmetically and seemed to drive fine untill yesterday. It seems when im doing about 40 mph or 60 mph the rpms drop betweem 1700 and 2100 and i get the shudder/buck. If i let of gas or accelerate it powers through but when in steady speeds in traffic it gives those issues. Let me know what you think? Ive read several posts here that start with a lot of minor work and end withtorque converter. Hope this isnt the case.
I have a 2012 and have replaced all the coils and plugs the purge valve the MAS sensor and had the throttle body cleaned and still have the same problem that hesitation will drive you nuts I’m no pro but I’m thinking this whole problem is the torque converter good luck with yours
 

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Just bought 2012 gmc acadia with117k on it. Mint cobdition cosmetically and seemed to drive fine untill yesterday. It seems when im doing about 40 mph or 60 mph the rpms drop betweem 1700 and 2100 and i get the shudder/buck. If i let of gas or accelerate it powers through but when in steady speeds in traffic it gives those issues. Let me know what you think? Ive read several posts here that start with a lot of minor work and end withtorque converter. Hope this isnt the case.
I recently had this same issue on my 09. in my case I changed all the injectors, sparks plugs, crank shaft position sensor, shock sensor, fuel pump, fuel pump control module and coils. And nothing changed. But it’s all came down to a minor issue. The green colored rubber ring/seal on the pcv situated on top of the engine was worn out. And finally when changed the engine runs mints and no more shuddering.
Try it.
 
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