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Unread 12-05-2012, 07:08 AM   #1
Wearyman
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2008 KK Liberty 
 
Join Date: Sep 2011
Location: Buffalo, New York
Posts: 141
Low speed "thunk"?

Hey all,

I've had this minor issue with my KK ever since I bought it. It only happens in a very specific situation, and otherwise doesn't bother me, so I've never had it addressed.

When I am leaving home in the morning, after I pull out of my drive and accelerate towards the end of my block, I notice that the car seems to "thunk" as I reach the end of the street. It seems to be coming from the transmission, and it causes the whole car to lurch slightly.

It only happens after first starting the car for the day, and ONLY if the RPMs reach about 2000 just before I let off the gas to stop at the stop sign. It seems like the car is wanting to shift to second gear, but it's not quite getting up to the speed it really wants to smoothly make the shift, and so the torque converter is causing the gear to drop in rather hard.

I should note that if I go just a tiny bit more gently on the gas and keep the RPMs down around 1500, it doesn't happen. The KK never leaves first gear and then I make my stop. I haven't been able to get it to happen at any other time once the KK is warmed up, and otherwise I have no issues whatsoever with the engine or transmission after almost 60K miles on the KK.

This is a 2008 KK, and it has ALWAYS done this. I had just assumed it was my own crappy driving style causing it, but then I read that it MIGHT be a TSB. However, I couldn't find any TSB that seems to fit this issue.

Has anyone else heard of or seen this issue before, or is it just the confluence of my driving style and the length of my street?

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Unread 12-05-2012, 07:34 AM   #2
rescue575
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2011 KK Liberty 
 
Join Date: Feb 2012
Location: Franklin Square, NY
Posts: 924
I have noticed this same thunk, though I really have t pin pointed when it actually happens. I have noticed that it is always during a low speed as you described.

Unfort I am not sure of any TSB on it.

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Unread 12-05-2012, 02:45 PM   #3
jonrjen
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2011 KK Liberty 
 
Join Date: Apr 2010
Location: Texas
Posts: 1,077
I maybe totally off here, but it sounds like you are right at a shift point on a cold transmission so the thunk does not sound like a defect. Keep in mind that with only 4 speeds to the transmission, the shifts are not near as smooth as say a newer design 5 or 6 speed automatic. Personally part of the reason I purchased the Liberty was for its old school 4 speed automatic. Shifting may be harsh, MPG may suffer, RPMs may find themself running higher before the shift point, but with only 4 speeds it almost never has a difficult time finding the grear it needs to be in.
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Unread 12-05-2012, 06:13 PM   #4
jsburton84
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2008 KK Liberty 
 
Join Date: Jun 2010
Posts: 169
The same thing happens to mine after a cold start.
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Unread 12-06-2012, 12:56 AM   #5
Drednot
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1991 YJ Wrangler 
 
Join Date: Aug 2005
Location: phoenix, az
Posts: 1,406
Mine has a similar cold driveaway quirk that only manifests itself on the odd short drive down my street, too.

I have the exact same opinion that jonrjen has.

Don't worry about it.
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Unread 12-06-2012, 06:38 AM   #6
Wearyman
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2008 KK Liberty 
 
Join Date: Sep 2011
Location: Buffalo, New York
Posts: 141
Wow. Ok, I guess I'm not alone then. Thanks for that guys. I wasn't terribly concerned, but knowing that it's basically just the KK and its working "as designed" puts my mind at ease.

Honestly, I haven't had it happen lately since I've trained myself to go a bit easier on the pedal in the mornings when I first start up. Nevertheless, its nice to know I don't have to worry about it.

Thanks!
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Unread 12-06-2012, 07:18 AM   #7
jonrjen
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2011 KK Liberty 
 
Join Date: Apr 2010
Location: Texas
Posts: 1,077
There ya go, sometime the CPU turns out not to be the smartest computer in the vehicle.....At times it is only a matter of the need to reprogram the drivers habits. The human brain is an amazing computer in and of itself.
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Unread 02-18-2013, 03:22 PM   #8
patrickkel1
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2008 KK Liberty 
 
Join Date: May 2008
Location: California
Posts: 10
I had the same problem with my 2008 Liberty with 50K miles. It got worse, eventually sounded like someone whacking the driveshaft with a sledge hammer. The whole vehicle would shake, and it worried me. The dealer re-flashed the shift-points in the memory of the computer, and the problem is reduced about 95%. I have adjusted my driving habits slightly to compensate for the remaining 5%. I do such a varied mix of driving that I wonder if the computer is perpetually confused when it is trying to adapt the shift points to my driving.
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