Overdrive hummming

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Apr 7, 2018 | 06:31 PM

Pana

Thread Starter

Newbie

Joined: Apr 2018

Posts: 2

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Year: 1998

Model: Grand Cherokee(ZJ)

Engine: 4.0

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?

Apr 7, 2018 | 09:33 PM

dave1123

Old fart with a wrench

Joined: Nov 2010

Posts: 14,398

Likes: 740

From: Manlius, east of Syracuse, NY

Year: 2000 XJ Sport & WJ Laredo

Model: Grand Cherokee (WJ)

Engine: 4.0L

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.

Apr 7, 2018 | 10:15 PM

Pana

Thread Starter

Newbie

Joined: Apr 2018

Posts: 2

Likes: 0

Year: 1998

Model: Grand Cherokee(ZJ)

Engine: 4.0

When I kick it out of o/d the sound goes away. It’s not the tires.

Apr 8, 2018 | 07:11 AM

dave1123

Old fart with a wrench

Joined: Nov 2010

Posts: 14,398

Likes: 740

From: Manlius, east of Syracuse, NY

Year: 2000 XJ Sport & WJ Laredo

Model: Grand Cherokee (WJ)

Engine: 4.0L

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!