Update: JK NP241OR sounds like a box of rocks—need help diagnosing 8.8 rear axle noise

M

motomick76

Guest
Update: Put axle together last week and still have noise. Today I put it up on stands, and what I thought was coming from axle was coming from my transfer case. Sounds like I need a set of bearings for the case, a rebuild kit. Issue is, who has one, or who has rebuilt one, and where did the kit come from. I have found a couple different kits, but nothing definitively saying they are for a JK241OR case. I have found two, but have subtle differences in the pictures:

Transmission Parts Distributors - NP241 or NP241J

Allstate Gear - NP241J

Anyone here know what to look for when getting a rebuild kit?



Decided to take an extended drive around Mt. St. Helens this weekend and in the 700 miles driven, noticed a noise from rear axle. It was readily apparent on long uphills pulling hard, and downhills using the engine for braking whirring sound. Also from a stop taking off, I can hear and feel in the shifter, best I can describe it as a tick, and speeds up as I accelerate. Confirmed it was rear axle as removed driveshaft this morning and drove around block with front axle engaged. No 'tick' and a lot less whirring sound.

A little backstory on axle:
  1. Detroit locker
  2. Revolution 4.88 gears
  3. New bearings, axles seals, everything in 2015
  4. Driven approx 2,000 miles total since rebuild

Got digging this afternoon, and pulled axles out and carrier. Could not find anything significant.
  1. Pinion - Tight, still preload drag on bearings, and spinning it feels smooth
  2. Carrier - Bearings and races appear great, spun by hand and cannot feel anything
  3. Pattern - i do not have enough experience to give opinion on the pattern or gears
  4. There is metal in the oil, as seen in the pictures
Experts:
  1. How is the pattern and gears? Is this abnormal or normal wear?
  2. What steps should I take next to determine noise and correct?

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CharlesHS said:
Have you checked the rear driveshaft U joints; they can produce vibrations and will make ticking sounds
Look for rusty dust coming from the cups.
Click to expand...

Driveshaft is a Adams unit, same age as axle, only couple thousand miles. Rigs has never even seen a mud puddle, just street and mild off-road few weeks ago.
 
Do you think the noise just started or is this a noise that was there before and you are just noticing it now? If it is a new noise then you need to try to figure out what might have changed.
 
Daryl said:
Did you replace the gears because of a failure?
Click to expand...

Did conversion 5 years ago, all I started with was housing, everything else was new 5 years ago, and put about 2000 miles on. There was no failure, upgraded from Dana 35 and went to 4.88 gears. Gears, bearings, locker, axles, brakes all new.
 
motomick76 said:
Did conversion 5 years ago, all I started with was housing, everything else was new 5 years ago, and put about 2000 miles on. There was no failure, upgraded from Dana 35 and went to 4.88 gears. Gears, bearings, locker, axles, brakes all new.
Click to expand...
What oil did you use?
 
Wildman said:
Do you think the noise just started or is this a noise that was there before and you are just noticing it now? If it is a new noise then you need to try to figure out what might have changed.
Click to expand...

I think it has been there since I rebuilt it. Hard for me to remember as I was having too many issues with supercharger and keeping it running I did not focus on that. Then it sat for 3 years until I got my conversion done this spring.
 
motomick76 said:
I think it has been there since I rebuilt it. Hard for me to remember as I was having too many issues with supercharger and keeping it running I did not focus on that. Then it sat for 3 years until I got my conversion done this spring.
Click to expand...
Can you catch your fingernail on this:
D361D3CD-28F8-47EA-A166-935E93390582.jpeg
 
Since you stated the rotating torque is within specs and it’s smooth when turning the pinion by hand, reinstall the carrier and perform a pattern check.
 
motomick76 said:
Decided to take an extended drive around Mt. St. Helens this weekend and in the 700 miles driven, noticed a noise from rear axle. It was readily apparent on long uphills pulling hard, and downhills using the engine for braking whirring sound. Also from a stop taking off, I can hear and feel in the shifter, best I can describe it as a tick, and speeds up as I accelerate. Confirmed it was rear axle as removed driveshaft this morning and drove around block with front axle engaged. No 'tick' and a lot less whirring sound.

A little backstory on axle:
  1. Detroit locker
  2. Revolution 4.88 gears
  3. New bearings, axles seals, everything in 2015
  4. Driven approx 2,000 miles total since rebuild

Got digging this afternoon, and pulled axles out and carrier. Could not find anything significant.
  1. Pinion - Tight, still preload drag on bearings, and spinning it feels smooth
  2. Carrier - Bearings and races appear great, spun by hand and cannot feel anything
  3. Pattern - i do not have enough experience to give opinion on the pattern or gears
  4. There is metal in the oil, as seen in the pictures
Experts:
  1. How is the pattern and gears? Is this abnormal or normal wear?
  2. What steps should I take next to determine noise and correct?

View attachment 191198
Click to expand...
What’s up with the back right side of that bearing cage?
 
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