42rlr overdrive hum 2012 KK

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Grey Liberty

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Just purchased a 2012 Liberty Sport. Have noticed a waa waa hum going up slight grades.Noise stops it I hit tow haul to lock out overdrive or just let off acceleration. It only happens about 50mph. Any one else have this problem or know of a fix. Thanks in advance!
 

Grey Liberty

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Just purchased a 2012 Liberty Sport. Have noticed a waa waa hum going up slight grades.Noise stops it I hit tow haul to lock out overdrive or just let off acceleration. It only happens about 50mph. Any one else have this problem or know of a fix. Thanks in advance!
Typo on title meant 42RLE
 

lfhoward

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Sounds like the engine is lugging a little maybe… are you at low RPM’s when this happens?

There was a TSB (technical service bulletin) for something like this on the early year KK’s, but I am sure it was sorted by 2012. For the 08/09 years that had this issue, Jeep reflashed the computer to adjust the shift points slightly.

Do you know the last time your transmission had its filter and fluid changed? That might be what I’d try first, if it has never been done. Transmission fluid has friction modifiers that can wear out if the fluid is very old, leading to transmission shudder. Your other option is to try a bottle of “Instant Shudder Fixx” from your local auto parts store. This has eliminated the low RPM shudder in mine, which started over a year ago now. It took like a week to work, so it wasn’t “instant”, but I am happy with it.

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lfhoward

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Also check the boot on the rear CV on the front drive shaft where it connects to the transfer case. This is a common failure point, where the rubber boot cracks, it shoots out all the grease, grit and dirt gets in, and wears down the joint. This could also be the source of a harmonic hum or other noises too. If it’s toast, the replacement CV joint is only like $40 on Driveshaftparts.com.
 

Grey Liberty

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Thanks you for your fast response! Transmission fluid changed at 34000 it now has 71000 miles. Yes that is good advice I'm going to take it to a well trusted ****** shop for a complete checkup. Fluid filter all cv and u joints. I agree with lugging theory. It does feel like driving a stick shift just before it should be downshift time going uphill. Just bought this well cared for KK that has all dealer service it's whole life. I've owned 10 Jeeps and this is number 11. Hope it turns out to be a good one too. Thanks again.
 

Grey Liberty

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Transmission shop well trusted said additive used was something like Trans X . Very strong cleaner caused lots of sludge in pan...sooner or later it will need rebuilt.I opted for sooner.
 

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