Rear Differential "Clunk"

[Maslin]

If I pull the rear cover will I be able to see the part of the axle that gets the wear?

No, it's the other end. You would need to raise the wheel on that side and "lock" the inside of the axle still. Then turn the wheel to see if there is play.

This is a good axle (as far as play goes). The spline wear occurs at the hub end. Should be a press fit, these aren't coming apart without a press.



These are worn splines. When they're clunky the axle and hub will just fall apart. Eventually, the splines on the hub turn to dust and it's just a smooth bore.

 

[jonblack]

OK gotcha! Thank you for taking the time to share your knowledge and provide detailed pictures...above and beyond!

 

[goldihop]

I've always been under the impression it is the outboard end of the axle at the hub that gets loose, but this video is showing it at the pumpkin...

 

[Maslin]

I've always been under the impression it is the outboard end of the axle at the hub that gets loose, but this video is showing it at the pumpkin...

I believe he’s showing that the wheel/hub spins much more than the axle at the inside, indicating play at the hub splines as expected. Can anyone help with the translation?

The spider gears are always going to have a bit of play. Assuming the pinion isn’t moving, turning one wheel will make the other wheel spin backwards.

 

[goldihop]

I believe he’s showing that the wheel/hub spins much more than the axle at the inside, indicating play at the hub splines as expected. Can anyone help with the translation?

The spider gears are always going to have a bit of play. Assuming the pinion isn’t moving, turning one wheel will make the other wheel spin backwards.

Ok thanks for the context. I was referring to the play where the axle is inserted into the side gear of the differential, but it sounds like that might be normal. Looking closely, that splined shaft coming into the gear seems to have a little play in it. I understand that the gears themselves will have some slop between them otherwise they wouldn't spin properly.

But like you said, a translation might clear up what they are actually talking about.

 

[Required]

Yes, the differential internals, including the inboard splines on the axle shafts that fit into the side gears, will have a small amount of backlash or “play”.

There is NO GREASE on the outboard hub splines (splines between axle shafts and wheel hub) and there SHOULD NOT be. It’s intended to be a dry interference fit. If anything, retaining compound applied during press assembly of new parts could help distribute stress in the joint and seal out oil that gets past the axle seal. If it’s already worn and has backlash, it’s dead.

 

[Required]

Is there way to inspect and see if there is play in the wheel hubs? Thank you!

You can jack up one side of the axle, take the wheel off, and check if your wheel hub doesn’t have a freeze plug installed in the center bore. If it doesn’t, you can see the end of the axle shaft outboard splines.

Make an indexing mark across the shaft end and the hub flange with a fine Sharpie. Disengage the parking brake (use wheel chocks), and then use a strap wrench or some other method to rock the wheel flange back and forth with a decent amount of torque. The indexing mark should not separate or shift at all. If it does separate, that means the spline joint has failed.

I’ve attached a screenshot from a video I took when I did this on my own van to show the gist of the process.

In my case it was very obvious because the wear was so severe. If you have a cheap Amazon inspection camera that records video, I found it very easy to see any movement by taping the camera head very securely to the inside of the wheel hub pointed at the indexing mark and recording while twisting the wheel hub back and forth.

Video:

 

[jonblack]

Wow...awesome information! Thank you so much for sharing. Now I know what to look for.

Having, said that, now that it has gotten colder, my clunk has all but gone away. I have adopted a driving style that minimizes the abruptness of the clunk upon take off so I only get the slightest bit of clunk (on occasion) in this cooler weather.

I may have to warm up the parts to exaggerate the condition.

Thanks again!

 

[Required]

Wow...awesome information! Thank you so much for sharing. Now I know what to look for.

Having, said that, now that it has gotten colder, my clunk has all but gone away. I have adopted a driving style that minimizes the abruptness of the clunk upon take off so I only get the slightest bit of clunk (on occasion) in this cooler weather.

I may have to warm up the parts to exaggerate the condition.

Thanks again!

You can also add a torque stripe across the axle shaft end and wheel hub the next time you remove the wheel instead of trying to observe backlash directly with my method above. If the torque stripe breaks by the next time you remove the wheel, you might have a problem there.

This might be good standard practice for mechanics and owners. Very cheap and easy to do.

Amazon.com

 

[Maslin]

I’ve never seen an axle missing the dust cap, although it would make it easier to check on.

If you have the slack back and forth, you almost surely have play in the hubs.

 

[Required]

I’ve never seen an axle missing the dust cap, although it would make it easier to check on.

If you have the slack back and forth, you almost surely have play in the hubs.

That’s what I thought but I got the opposite information elsewhere.

I have the crappy Currie axle and they didn’t bother reinstalling the core plugs, if they were ever there in the first place. Pretty stupid considering that leaves the splines open to water ingress… but no one at Owl or Currie listened when I tried to explain that to them 🤷🏻‍♂️

 

[depark]

That’s what I thought but I got the opposite information elsewhere.

I have the crappy Currie axle and they didn’t bother reinstalling the core plugs, if they were ever there in the first place. Pretty stupid considering that leaves the splines open to water ingress… but no one at Owl or Currie listened when I tried to explain that to them 🤷🏻‍♂️

That's Owl for you.

 

[yukonrider]

My 2019 with about 85k has been clunking for a while now, especially shifting into and out of gears. I already did the output shaft lock-tite with no luck.

Can I just pull the shaft out and inspect? If it falls apart, no good. Any special instructions or just remove wheel, brakes, bolts holding hub in and it all slides out?

I have 2 months where it can sit on jack stands so thinking pull and replace if needed left first, then right. EuropartsSD has them for 880 shipped, and WorldMercedes which I haven't heard of has them for 760 shipped, both allegedly genuine MB

 

[Rocksnsalt]

Mine too, pretty much always has and at around 95kmi now, 2 dealers say it’s normal. 🫤

Annoying.
The Best or Nothing!

EDIT:
To be clear, it’s when I put it in gear, or out sometimes. And I typically put the van in neutral and activate parking brake before putting it in park so the drivetrain isn’t “pre loaded”

 

[jonblack]

Can I just pull the shaft out and inspect?

I think it is possible to "inspect" without pulling the axle out.

My van clunks so I am going to reread this entire page, watch the videos again, and try to wrap head ahead where the actual noise occurs. I recall Maslin saying the wear occurs on the hub side, and I think if you take the dust cover off of the hub you will be able to see movement between the axle and hub. I am going from memory from reading this page we are on before, so I will do my research again before moving forward with inspection.

I didn't inspect when I read it before because mine doesn't really clunk in cool weather and only starts doing it about 85 degrees.

Just did a 2,800 mile trip in cool temps in CO and no clunks. Back home in the South it clunks and makes a lot more mechanical whining noises, especially as temps are in the mid 90s.

 

[jonblack]

If I ever get a chance to take my axle out, and it is worn enough to separate from the hub, I am going to try the "loctite fix" in this location.

Loctite 609 and 620 are bearing retaining compounds design for small gaps and are very strong. I have a good bit of experience using 609 in a previous line of work. 620 is stronger and can tolerate larger gaps.

It is probably a temporary fix but my clunk started with approximately 25k miles on the van, so before I put a new shaft in (and have the new one start clunking 25k later) I will see about putting a bandaid on it.

I do my own labor and love experiments like this, especially if it works and could help others in the future. It would be a different story if the replacement axles were $150 but at $800-1000 I will try bubble gum first.

I wonder if I can get the 609 to wick in without disassembling anything?

That gets me to thinking. If the splined shaft is press fit to the hub why can't you drive a key in the end and pin the shaft and hub together?

 

[yukonrider]

I wonder if I can get the 609 to wick in without disassembling anything?

One thing I noticed in all the (two?) pics of the separated hub/shaft combos is a thick rust color on the spline area. Makes me wonder if somehow water is getting in and degrading this surface or something.

I was going to spray some bearing retainer compound on the new ones when I get them to seal them up, can't hurt eh?

 

[yukonrider]

View attachment 388464View attachment 388466

These are the pictures I was referencing above. That's a lot of rust for a sealed axle

 

[yukonrider]

I removed my lug covers and tried to remove the dust cap to asses spline movement , it is rubber over metal so didn't move with non-destructive force.

I couldn't find just that cap the one place online I looked so I didn't upgrade to destructive force. Anyone know if they're sold on their own?

 

[Maslin]

I don’t think any parts are sold. It’s an assembly from Mercedes.

Someone makes it, so there are parts. Good luck figuring that out…