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In regards to the 'vibration' noise coming out of the rear axle, did you change out the pinion seal on the rear axle? If too much torque on the pinon nut will cause a vibration during acceleration, as well as, not enough torque on the pinion nut will cause a vibration on deceleration(letting off the gas pedal). Check your torque specs on the rear axle's pinion nut if you changes out the pinion seal.
 

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1998 Jeep Cherokee xj sport w/4.0 auto D30 front and 8.25 rear 6” rubicon express lift fox shocks
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28 Posts
Discussion Starter · #22 ·
Do not add to the t-case drop. They actually put a lot of strain on the motor mounts. the front drive shaft is double cardan. you can adjust the front pinion angle with adjustable control arms. a 6.5" lift should have come with adjustable control arms. it doesn't look like yours did. they extra angle has stressed the u-joints and the vibration is probably what caused the seal to fail. you can change it. You have to pull the pinion flange off, but make sure and mark the nut on the pinion shaft, so you can get it back in the same position and same amount of torque. Some Dana 30's use pinion shims for preload while others use a crush sleeve.. If you don't get the torque right you can ruin the pinion bearings and they general take out the ring and pinion. at 6.5" of lift you need a SYE, and a double cardan rear drive shaft. I put in a hack n tap and ran a used front driveshaft on the back of mine for years.
I do have after market lower control arms on the front but they’re not adjustable and now u mention it the new front springs to have a slight arch or curve in them and my bump stops are in different spots in other words one is closer to the spring then the other is I’m not at 6” just yet it’s 5.5” I do have 1/2” spacers to install which I forgot to do when I installed the springs. As far as the pinion seals all I need to do is remove driveshaft and pinion flange pop out the old seal and install the new one right??…is the rear the same?
 

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1998 Jeep Cherokee xj sport w/4.0 auto D30 front and 8.25 rear 6” rubicon express lift fox shocks
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28 Posts
Discussion Starter · #23 ·
In regards to the 'vibration' noise coming out of the rear axle, did you change out the pinion seal on the rear axle? If too much torque on the pinon nut will cause a vibration during acceleration, as well as, not enough torque on the pinion nut will cause a vibration on deceleration(letting off the gas pedal). Check your torque specs on the rear axle's pinion nut if you changes out the pinion seal.
I never touched the pinion at all just removed and reinstalled the axles when I did the disc brake conversion and I did the axle seals to that’s it
 

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1998 Jeep Cherokee xj sport w/4.0 auto D30 front and 8.25 rear 6” rubicon express lift fox shocks
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28 Posts
Discussion Starter · #24 ·
Do not add to the t-case drop. They actually put a lot of strain on the motor mounts. the front drive shaft is double cardan. you can adjust the front pinion angle with adjustable control arms. a 6.5" lift should have come with adjustable control arms. it doesn't look like yours did. they extra angle has stressed the u-joints and the vibration is probably what caused the seal to fail. you can change it. You have to pull the pinion flange off, but make sure and mark the nut on the pinion shaft, so you can get it back in the same position and same amount of torque. Some Dana 30's use pinion shims for preload while others use a crush sleeve.. If you don't get the torque right you can ruin the pinion bearings and they general take out the ring and pinion. at 6.5" of lift you need a SYE, and a double cardan rear drive shaft. I put in a hack n tap and ran a used front driveshaft on the back of mine for years.
Unfortunately I bought the lift separately meaning not a complete lift kit the rear leafs are 4.5” plus 1.5” shackles for 6” and the front springs are 5.5” and I’ve got 1/2” spacers to install for 6” total I’m gonna get the shims for the rear and now it looks like I need to buy adjustable lower control arms for the front as I now know that the front axle is rotated to far forward which explains my springs having a slight arch in them but thanks to your info and advice I can now fix the problem….when I did the front springs I left the upper and lower control arms attached should I have at least loosened them ?
 

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1998 Jeep Cherokee xj sport w/4.0 auto D30 front and 8.25 rear 6” rubicon express lift fox shocks
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28 Posts
Discussion Starter · #25 ·
In regards to the 'vibration' noise coming out of the rear axle, did you change out the pinion seal on the rear axle? If too much torque on the pinon nut will cause a vibration during acceleration, as well as, not enough torque on the pinion nut will cause a vibration on deceleration(letting off the gas pedal). Check your torque specs on the rear axle's pinion nut if you changes out the pinion seal.
Would you or anyone else happen to know what the torque specs are on the front and rear pinion nuts so I can do it right after I replace the seals?
 

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If you are only replacing the pinion seal, "generally" you would mark the pinion nut and the pinion and put it back in the exact same spot. But if the pinion was not installed to the proper torque to begin with. It won't matter anyhow. Pinion nut torque is determined by the rotation torque on the pinion shaft and preload on the pinion bearings. as you turn it. this can only be done with the diff carrier removed. Dana 30 rotational torque is ~15 -20 inch lbs. and the c8.25 is ~15 - 25 inch lbs. these are specs for new bearings and are 6-10 and 10-12 respectively. I have had to literally stand on a pipe to turn a pinion nut in order to achieve the proper pinion bearing pre-load. These types of setups (Some dana 30's and dana 44's) have a crush sleeve which is used to maintain proper pinion bearing pre-load. The dana 30 in my jeep uses shims to achieve pinion re-load.

If you pull the drive shaft grab the pinion adapter and shake it. see if it has any play. If there is no play, you can get way with just replacing the seal. If you feel any play, you may have internal issues that need addressed. You "May" be able to get away with just tightening down the nut until the play is gone.

Here is a link to Bleeping Jeep Yoke wrench tool which I have bent trying to torque a dana 44 on a JK.

Torque spec on a Dana 30 is between 160-200 ft-lbs.
C8.25 is 210 ft lbs.
 
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