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Overdrive hummming

Old 04-07-2018, 06:31 PM
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Year: 1998
Model: Grand Cherokee(ZJ)
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Default Overdrive hummming

Hi everyone I am new, and this is my first post. I have a 1998 ZJ Laredo in a 3.5” rough country loft on 33” bf All terrains. At 55mph the Jeep kicks into overdrive and the Roma frío down to 1500 and then there is this drone sound that takes place like a propeller airplane. When I reach 65 mph the Rpms start jumping from 2000 to 1800 but there is no jerking when driving. I was planning on changing the transmission filter and flushing it. Maybe even the selenoid. Thoughts?
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Old 04-07-2018, 09:33 PM
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I suspect the trans is going into and out of O/D because of the added torque required to turn those 33s. It could be just the converter clutch. The sound is probably the tires. Just my opinion. Try locking out O/D and see if it makes a difference.
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Old 04-07-2018, 10:15 PM
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When I kick it out of o/d the sound goes away. It’s not the tires.
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Old 04-08-2018, 07:11 AM
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Okay, try this. See if you have engine braking by downshifting to 2nd at about 30 mph. If you don't, the overdrive unit may need work. There's a snap ring in it that sometimes breaks allowing the 800 lb spring to press on the overdrive sprag clutch. To verify if the snap ring is broken, remove the trans pan and it will be in 2 pieces in the bottom. The O/D unit will unbolt from the transmission without removing the trans from the jeep. If it IS broken and you want to fix it, come back and I'll explain how to remove it without killing yourself by releasing that spring!
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