Torsen Groan

[3onthetree]

Hi everyone, I have a two part question I hope someone more knowlegable than me can help...I did a Torsen Diff drain/fill at 10k miles using the Ford Spec Motorcraft 75w-85 oil. I should have measured the level before draining, but did drain 1.5 L. Like the spec says and refilled same amount. The oil should be 9mm (.35in.) below the drain hole when filled, but I’m measuring about 12.5mm (.5”) so add more? Or leave as is?
My other concern is I now have a groan from the diff when making low speed sharp turns while accelerating. If I understand correctly, the factory fill contains XL-3 friction modifier regardless of whether the diff is LSD or Torsen, but the off the shelf fluid does not. The Torsen site says friction modifier is not needed, but can be added if the “groan is objectionable”
Anyone have experience with this?
Oh..and the old fluid did not smell like it contained modifier, which smells really bad.
Thanks, Frank

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[thelostotter]

I used Mobil 1 75w-90 synthetic gear lube and XL-3 when I replaced the fluid in my Torsen equipped differential. Have not had any groaning. The used stuff I drained out stunk pretty bad but the replacement XL-3 didn't smell as bad as I was expecting.

 

[3onthetree]

Thanks, what was your fluid level before or after? ...yesterday I removed 4oz. and replaced w/4oz. of xl-3. and then began replacing fluid, measuring after each oz. added. Added 3.5 oz before level was close to 9mm. from hole. Hope i didnt overfill...1.5L+3.5 oz. Drove aro 50 miles and noise is gone.

 

[CB18]

I don't know why a Torsen would call for friction modifier. There are no clutch packs in a Torsen differential.

 

[3onthetree]

Got my info here: https://torsen.com/tbr-lube-friction-modifier/
“...This begs the question of whether or not friction modifier is actually necessary in a Torsen. Like I said earlier, the modifier is beneficial in smoothing out the operations of friction devices. However, because our friction properties are different than that of a clutch plate differential, you might not see the same symptoms of stick-slip behavior that those would. As noted, clutch plate differentials have a distinct tendency to chatter without friction modifier in the oil, and that chattering can become very objectionable. So, the modifier is essentially a requirement.

In a helical gear diff, however, the stick-slip tends to show up as an audible noise, described by some as a “rusty screw” noise, or as a squeak or moan. You tend to hear it in very low-speed turns, when the steering is at or near full-lock. So, you might hear it while maneuvering in a parking lot, or turning the car around in your driveway. This noise is, as I said, just a characteristic of the friction properties, and is normal. But, if you hear it a lot and it annoys you, adding a few ounces of friction modifier to the axle lubricant will almost always eliminate it. So, the bottom line is it’s up to you.”

 

[alanpv]

I think you're missing the 4oz of friction modifier?

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