Calling on all of you axle experts.

About a year ago I picked up a C8.25 with 4.10 gears to swap into my 2000 XJ with a turdy 5. (4.0 | NP242 w SYE | 3inch lift 31's)

Decided to rebuild the axle with new bearings all round - the kit was from Yukon and included absolutely everything. Note: I USED OLD GEARS

Everything was done to spec. Rotational torque on the yoke, backlash everything was perfect. Gear pattern looked full, but was to be expected with used gears.
After about 2000 miles I started noticing a noise at low speeds and after a couple long trips and extended time on the freeway the noise has gotten really bad particularly on deceleration.
I stuck a go pro under the jeep, check it out here:


Ive taken the diff cover off and everything looks perfect, zero metal filings, all good.




- Backlash feels fine, borrowing a dial gauge to double check.
- Pinion has absolutely no forward and back play, could feel a tad loose in terms of rotational force, however its hard to tell with the tyres on and carrier still in place, as I think the tyres are spinning it.
- I've also run the jeep on jack stands but could hear nothing with a stethoscope, must only happen under the weight of the vehicle.
- Topped up oil on a hill to account for the pinion angle

As I mentioned everything was installed properly, only way of knowing for sure is tearing it apart and checking everything.
I've read about a cracked crush sleeve, but I doubt thats the case, it is Yukon products after all.

I'm leaning towards it simply being the old worn gears that are now running outside of their original wear pattern.

Has anyone experienced this? Is there risk of explosion or should I just turn the crappy xj radio louder?

 

What happened to the one you used to rebuild it the first time?

 

Anyway, sounds absolutely like pinion bearing noise.

 

Easy captain, my mechanic mate who helped me has one and I borrowed it.

Anyway, backlash is currently at 0.013mm / 0,0005in perhaps a bit too tight. Spec is 0.0006- 0.0010in. I remember we set it tight because it was used gears, but maybe that was the wrong approach - Gonna start with that.

Also checking wear on the pinion, does it look too par back? I reused the same (oem) shim I pulled it out with.




I know that noise on deceleration denotes pinion bearing, but they're brand new timken bearings, pinion is not loose, so not sure how they could wear that quick.

 

0.006 to 0.008 inch, but whatever.

Not any more.

 

Whatever

Remember now why I don't post on these forums anymore

 

Well thanks so much for coming. Pick up your lovely parting gifts on the way out!

 

OK I can't stand unresolved threads! So...

Your specifications are not correct. They're a decimal place off. If you set it that tight it would barely turn. See values and note the decimal places:



However, when you used the dial indicator, you misread it. It's actually 0.13, not 0.013 mm:




Bottom line, backlash is normal.

 

You're right, I made a typo, it was a decimal place out.
Look, I'm no mechanic, just a guy trying to fix his own junk using information off the internet.

I reset the backlash last night to 0.20mm (8 thou) on the looser side to see if it makes a difference.
However setting the preload on the carrier bearing, got me thinking I didn't do it right the first time.
I remember when I originally set it up I couldn't achieve the 75ft lbs on the preload adjuster, I think the bearing caps were on too tight. I thought it would be fine...
This time however I managed to do it right.
Anyway, will put the wheels back on and test today, if it isn't solved I'll tear apart the whole thing again...sigh

 

Kinda makes sense now why I wanted to see the old dial indicator, don't it?

Seems to me you would have noticed a variation in the backlash then, and even more so now.

IMO this is significant. Seems to me only 2 things would have a bearing (see what I did there?) on that-- wheel bearings and pinion angle.

Check wheels bearings carefully.

What's the pinion angle, both static and wheels off the ground? From the GoPro looks to be -0- which is odd with a 3 inch lift. Did you put wedges in there (that's my assumption, as you knew to overfill the diff).

 

Making the assumption (perhaps wrongly so) that if there was no weight under the vehicle, the jackstands were under the unibody and not under the axle.

 

Ok, so I got it all together and took it for a test. The noise has changed pitch, but is still there on acceleration and deceleration.
At first I thought it had gone at high speed because I couldn't hear it, but I shot some video again to be sure and still sounds rank, however not as loud.

This is on the same stretch as road as before going at same speed - note when taking off it has a rattling noise - that was present on the other video, I just didn't include it, but perhaps wheel bearing?


Here is a video at slower speeds when noise is now more prominent, tried to swerving to check wheel bearings.


One thing to note axle shafts are also old, blue and have grooves where it rides on the bearings.




IMO this is significant. Seems to me only 2 things would have a bearing (see what I did there?) on that-- wheel bearings and pinion angle.

Check wheels bearings carefully.

The wheel bearings are new, didn't check them before I put it back together like an idiot. I initially wrote them off, but it could be the old shafts now riding on fresh bearings? I dunno.

What's the pinion angle, both static and wheels off the ground? From the GoPro looks to be -0- which is odd with a 3 inch lift. Did you put wedges in there (that's my assumption, as you knew to overfill the diff).

[/QUOTE]

Pinion angle is around 14 degrees if I remember correctly. I moved the spring perched - have an SYE.
Filled oil to factory spec.

The main thing thats puzzling me is that the noise has definitely changed. At high speed its quieter, in fact I can barely hear it in the cab and when driving slowly its there at acceleration and deceleration.
So what I've done has definitely done something.

Thats where I'm at right now, might need to sleep on it.

 

Ewww.

I would paint (or use Prussian blue) an inch or 2 of the ring and check the contact of the pinion. The contact area should be centered.

Normal is about 1 to 3 degrees, but I'm not sure if we're talking about the same thing. It's the angle of the driveshaft to the face of the yoke.

 

Angle 2:

 

so I have the bottom setup. A slip yoke eliminator in the Transfer case and a CV drive shaft.

yoke angle is -1 to account for axle wrap and DS angle is around 14 degrees.

ive found a few old threads of someone going through the exact same thing, they disassembled everything and all was good and it ended up being gear noise reusing old gears with new bearings. Eric the car guy (YouTube) had the same issue, check out vid.

Think i May close the book on this for now. I’m actually just about to stick a turbo on my 4.0, so this is getting in the way lol! Plus I’m sure the extra power will help me find where the noise came from real quick.

thanks for you input Dave. Sorry for getting moody