Metal Shavings in rear Differential

[iceman14n]

My rear differential fluid has metal shavings ...

I felt constant level of vibrations sometimes when i got over 70 km/h to 110km/h and everything feels smooth. So my mechanic diagnosed the problem, suspension, bushings and u-joints/drive shafts and everything was perfect but then he decided to see the fluid level in the rear diff and he saw some metal pieces come out (microscopic really).

So now, my prognosis is that the metal shavings might have been there since the time of the break in because i know the fluid has never been replaced in the transmission nor the diffs.

What do you guys think

[yeldogt]

So ..................are you having a problem with the differential?


Depending on the miles -- having some small particles should not be a problem. The lower plug may have a magnet to catch them so they don't do any more damage - I forget if the Path does -- I get my cars mixed up

Now -- if the fluid was low and the shaving many then you may have some damage ............. it is often cheaper to install a used rear then to fix the one you have. Normally, as long as the fluid level is maintained they last forever.

[Towncivilian]

I ran the factory fill for 125k miles, no problems with the rear diffs. I'm sure having all the break-in material floating around for so long isn't the smartest idea, but I wouldn't worry about it. The drain plug is magnetic, not sure about the fill plug.

[Densetsu]

The rear diff only has a magnet on the drain plug, not the fill plug. How did he find the shavings? Did he do a drain and fill, or just stick his finger in the fill hole and feel the top of the oil? Some shavings are normal, but those are usually caught by the magnet and don't float around in the oil.

Does this happen with OD off?

[iceman14n]

Well i basically asked the mechanic to see what is the vibration coming from (from 80km/h -110km/h) and he basically concluded that it is the diff... i have my doubts because differential needs to be abused to be f*ked.. but i have been driving pretty nicely.

my concern is the vibration, The Driveshafts are fine, suspension is fine, tires are balanced alignment is done.. I just dont get it...

[ARKQX33V6]

Iceman, you have a LSD CORRECT? As a limited slip the lock up portion of the system requires a hypoid with modifiers to help grab through friction.

Test out your limited slip action, reaction by raising the rear end both wheels off the ground. In neutral all off brakes all off turn the one rear wheel and check that the other turns in the same direction.

The metal flakes you talk about are usually brass colored should not be steel. Drain the diff completely, examine the drained hypoid fluid. Fill with new LSD oil and retest the rear end as above.

Without removing anything from the rear end drive it for a week, drain the hypoid oil and check for floating metals in this week old fluid, if none, refill and test within a year..

The rear ends are quite robust and quiet, does your limited slip diff make noises while working, can you turn sharp turns, full lock with some rumble back there and the tires rubbing hard on the road surface...this is normal with a limited slip rear end.

With the rear end up check the bearing seals at each wheel for hypoid leaks coating the rear brakes.

LSD need the correct modified hypoid oil and change it regularly, hypoid oil is honey coloured when black it has been in service too long. Doing a 2 year interval for all oils is good for PM.

[iceman14n]

thank you ARKQX33V6... Mine is an LSD...

i am geting the fluid replaced and i will see myself what that old fluid looked like, My mechanic doesn't do transmission stuff so he adivced me to go to a transmission guy.

Do you think i can do this myself, i am pretty mechanically savy but this i thought should be done by a pro... then again they will be charging me a crap load too..

What do you think? i will need a pump to fill in the fluid tho right...

[Densetsu]

The differentials are easy to do. All you need is a 1/2" socket wrench with a short extension, an oil pan, and a pump or syringe to fill it. A breaker bar or torque wrench is recommended though, because often the plug is siezed/frozen and you need the extra leverage. Some recommend wrapping the tip of your extension with tape for a tighter fit in the plug, because there have been cases where they've stripped the plug and had to go to extreme means to get that screw out. (I believe it involved welding an extension to the plug.) Tread carefully.

Also, it's not a bad idea to try and remove the top plug first -- no sense in draining the fluid, then finding out you can't get the fill plug off.

I use this grease gun style syringe to transfer the fluid in; others have their own solutions that work equally well. All I can say is the simpler, the better. I tried a complex pump and it failed horribly; a simple syringe worked simply and effectively for a fraction of the cost.

Oh, and it'd be prudent to buy an extra quart or two of gear oil, because your first time doing this you'll probably spill a decent amount on the ground.

Edit: Here's the awesome post I was referencing above.

[cpta2020]

Well I Have a vibration thats starts around 70km to 110km, I have replaced all fluids, replaced rear driveshaft, New tires and balance... and its still there.. this is driving me nuts and costing me a lot of money... let me know what you find with your vibration

[asoomal]

Iceman, you have a LSD CORRECT? As a limited slip the lock up portion of the system requires a hypoid with modifiers to help grab through friction.

Test out your limited slip action, reaction by raising the rear end both wheels off the ground. In neutral all off brakes all off turn the one rear wheel and check that the other turns in the same direction.

The metal flakes you talk about are usually brass colored should not be steel. Drain the diff completely, examine the drained hypoid fluid. Fill with new LSD oil and retest the rear end as above.

Without removing anything from the rear end drive it for a week, drain the hypoid oil and check for floating metals in this week old fluid, if none, refill and test within a year..

The rear ends are quite robust and quiet, does your limited slip diff make noises while working, can you turn sharp turns, full lock with some rumble back there and the tires rubbing hard on the road surface...this is normal with a limited slip rear end.

With the rear end up check the bearing seals at each wheel for hypoid leaks coating the rear brakes.

LSD need the correct modified hypoid oil and change it regularly, hypoid oil is honey coloured when black it has been in service too long. Doing a 2 year interval for all oils is good for PM.

Always thought they had VLSD...

[Gregk604]

I know this is an old thread, but I am having the exact same symptoms. Maybe someone has any advice?

-Only vibrates between 80km - 110km and feels like it's coming from the rear end
-Rotated tires and tried the spare
-Pulled both drive shafts and confirmed Ujoints are tight and not binding
-Pulled the drive axles and confirmed bearing has no play
-I did a full fluid change, I didn't see any metal in the diff oil
-I even had a Nissan tech test drive it and he blamed it on the 4x4parts bushings or said I used the wrong oil in the diff - then charged me 1hr labour.

Next step is to take it to a diff shop but i'm afraid of what they will quote. Or drive it until it shakes apart.

[4xq]

Please tell us year and whether you are 4wd or 2wd. Just to be sure we are talking R50 4wd. Also, tell us exactly which bushings you already replaced.

[Gregk604]

Yes, is a 2002 R50 4wd. I replaced both upper and lower control arm bushings with the poly split design. The vibration became noticeable after installing the new ones but I suspect it was always there but my old rubber bushings were softening it. I emailed with Mike at 4x4parts and he didn't see how the bushings could be the cause of the problem.

[4xq]

Thanks for the info!

Tis late - the only things I can think of right now: Blown shock absorber. Two, how did you tighten up the control arms? The truck is supposed to be on the ground when you tighten all the nuts up. If you happened to do it with the wheels in the air, the bushings will be under stress as you drop the truck and the suspension settles.

Could also be you threw a balancing weight off of the driveshaft - pretty rare, but I guess we are probably looking for anything here.

Off to bed!

[rgk]

Regarding this issue, I have been seeing some talk here lately regarding front differential mounts being the culprit.

[Gregk604]

So I bought some new rear shocks - I still had original with 200k+ kilometers. I can't see how blown shocks would cause the same vibration only at certain speeds but maybe. Next step will be balancing the rear drive shaft.

[4xq]

Before you balance the shaft, unbolt it from the differential, and spin the differential flange 180 degrees. Then bolt it back up and see if it changes anything.

I'm kind of assuming with 200+ km the truck has had u-joints at some point? In that case the shaft may need balancing.

You might also check your rear transmission mount. That is an anti-vibration type mount.

[Gregk604]

So I just checked my rear transmission mount and it looks split. Good idea on rotating the driveshaft, i'll give that a try if the transmission mount doesn't fix my problem. I put on new rear shocks, it didn't solve the vibration but definitely dampened it some.

U-Joints haven't been done, they are still original. I had both shafts out and confirmed they are not binding and don't have any play. If they were bad I assume I would feel it once I had it out?

http://postimg.org/image/44497vr73

[4xq]

Yep, transmission mount has some issues. You really can't tell just how bad it has deteriorated until you get it out though. I swapped that out on my QX4 - I just held the transmission up with a floor jack and pulled the crossmember out. Took all of 30 minutes.

You are getting your moneys worth out of the U-joints. But if they are tight and smooth, then they should be fine. It's not unusual at all to feel binding on joints that old.

How are the bushings in the panhard rod?

[Gregk604]

So I just finished changing out the transmission mount and putting in new struts & strut bearings. It drives ALOT better but I am still having a slight vibration from the rear between 90km - 100km. Outside of that speed everything is just fine. I'm back to thinking this might be tire balance. I don't have much faith in the Nissan Dealership who charged me 1 hr labor but couldn't even find the busted transmission mount. They said they balanced the wheels but who knows... Off to the wheel shop tomorrow and then I will try flipping the drive shaft 180 degrees.