Grinding/chatter in BMW e46 XI (AWD) differential, add LM Mos2 or Motorcraft LSD additive?

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Feb 9, 2019
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Hi all,

I have some front end grinding that's going on between where my front differential is and the left wheel. Seems like grinding + some sticking (wheel bearings replaced not long ago, no change).

I change the differential oil about 2 y ago ( at a shop) and about 2 mo ago again (myself). Didn't see any particles in the old oil 2 mo ago.
Both times it was changed to RedLine 75w90. The grinding was there before the last diff fluid change, but since the last change it seems even worse.
Not sure why. I wanted to change again and this time go with: https://www.fcpeuro.com/products/gear-oil-liqui-moly-99991754600, as well as adding a friction modifier.

I read that adding LSD additive to a non-LSD additive should do anything bad. But, since I don't understand the mechanics in differentials too well, I was wondering if something like the Liqui Moly MoS2 additive https://www.amazon.com/gp/product/B00CPL8UPY/ref=ox_sc_act_title_2?smid=A3NWIEOAD4STBF&psc=1 would be better (which apparently is bad for LSDs), or go with the well proven Motorcraft additive (https://www.amazon.com/gp/product/B...&pf_rd_p=edaba0ee-c2fe-4124-9f5d-b31d6b1bfbee)

Thanks for your input!
-fana
 
The dynamic traction control on these cars is heavenly to guide it around corners. My X1 s28i with only rear ediff wore rear brakes and tires twice as fast as front. In my old Japanese car world rear brakes NEVER wear out. Here's what happens. You jump on gas and right rear slips.....brake on that side instantly grabs and tire slips again because brake locked. That sends the power to left side where that side slips. It's like a loaded launch. I put ceramic brakes on rears only and stopped that. Also stopped the excessive brake dust.

Imagine the pressure that traction control is putting on the drive train of even fronts drive. Do yourself a favor and buy some Akebono Euro ceramic pads, and slow your brake cost at same time. Also, they are linear feel instead of grabby.
 
RedLine has friction modifier in it already. I agree it's something else if you got no metal when changing the gear lube.

Thanks for your replies. I guess I won't change the gear lube again then.

@40w8. You comment seems a bit off topic but just fyi, I'm on recently rebuilt brake system all around with akebonos, but I'll double check the front brake assemblies to make sure that everything is in order.

Cheers,
-fana
 
I'm guessing the CV joints. I ran a 2004 X3 to over 200k without touching the diffs and it's still running fine according to the friend I sold it to.
 
"Grinding + sticking" - that sounds like a binding CV shaft(s) to me. Have you had both wheels up in the air and rotated by hand to listen and visually inspect where the noise is coming from? Does it happen worse when turning?
 
I'm guessing the CV joints. I ran a 2004 X3 to over 200k without touching the diffs and it's still running fine according to the friend I sold it to.
Thus, why I mention turning down the dynamic cornering on these cars unless you have to feel it on driving hard. It's brilliant, but will cost some wear in drive train.
 
Yep, the engine torque trying to spin a wheel trough one end of the CV shaft, braking pads gripping to slow it down on the other end... puts a lot of torque strain on both the CV joints.
 
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