Bad Vibrations with Grinding

Old Mule

Old Mule

New Member
Joined
Jun 7, 2021
Messages
8
Location
Lafayette Indiana
Hi folks, I am new to the forum, it looks like a great place for information and help. On that note, I am having a major issue. I have an 05 Rocky Mountain Edition with 80k. Recently on the way to the store without any warning i developed a bad vibration, bad enough to shake the dash out of the jeep, not a lateral shake like a shimmy but rotational hop, shaking up and down, with a rotational grinding noise as well I had already planned a new clutch so I installed that, did not take care of the problem. I took the front drive shaft out, no change, reinstalled the front and removed the rear drive shaft, put it in 4 hi and drive around the symptoms go away completely, then I reinstalled the rear shaft and left it in 4 Hi and the grinding noise get 100 times worse especially while you are turning and the vibration is still present if you drive it in a straight line I am pulling my hair out on this one so any help would be wonderful . Thanks in Advance
 
Old Mule said:
I took the front drive shaft out, no change, reinstalled the front and removed the rear drive shaft, put it in 4 hi and drive around the symptoms go away completely, then I reinstalled the rear shaft and left it in 4 Hi and the grinding noise get 100 times worse especially while you are turning and the vibration is still present if you drive it in a straight line I am pulling my hair out on this one so any help would be wonderful . Thanks in Advance
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From you description you could have a problem in the rear differential. When power is applied the problem is worse which could indicate a pinion bearing problem.
Is the rear differential pinion seal leaking where the rear driveshaft bolts to the pinion yoke ?
Chock the front tires, Jack up the rear of the Jeep and place jack stands under the axle tubes; remove the rear driveshaft and spin the tires listening for the grinding sound inside the pumpkin section.
 
I have opened the diff up and had a look around,does not appear to have anything going on gears mesh fine spider gears have a little galling on them but no issues spider gear shaft has just a tiny bit of play in it but nothing terrible pinion seal is not leaking and has no play in it and i have jacked itr up and spun the wheels, no unusual noises that is why i am stumped on this one
 
Take your drive shaft off and check to see if your output shaft on the transfer case is bent. if so there ya go. it can be hard to tell but i just put in gear and watched it. have someone mess with the gas and see if its moving odd
 
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I have done that too. I didnt see anything out of round. Thats what makes this a mystery it just started , rolling down a flat road first the vibration then the grinding and now if you put in 4 hi the grinding is terrible
 
Well transfer cases are not that bad to crack open. what i did was take drive shafts off and hook my drill to my front yoke nut and simulate it. you may want to take off that transfer case and check some chain slack gears yada yada not that bad really.
 
take off all drive shafts and get that yoke spinning in all your transfer case gears see if u can simulate it leave your trans in neutral if there is an issue with the transfer case you will know pretty quick
 
Try this - put it in 2WD and lift the rear wheels off the ground (block the fronts!). Start motor and put in gear. If you don't hear any grinding, judiciously add some gas and brake at the same time to load the drive train. If this recreates the grinding noise you may need a second person to find where it's coming from.
 
4 lo or 4 hi with both drive shafts in take the rear shaft out with it in 4 hi and all the symptoms go away you can drive it at 40 50 60 0r 70 with no symptoms
 
Have you checked to see if your pinion nut has backed off slightly and what your pinion preload is currently?
 
Did I mention that the grinding noise while hard to pinpoint sounds like it is coming from underneath the middle of the jeep, And thanks for the torque specs Charles
 
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