Diff Fluid for Track

[Digitalwave]

I'm running a regular-old E30 M3 4.10 LSD in my track car, and I have been running Redline 75w90. I've been considering switching to 75w140 since it's a dedicated track car, and it got me thinking about LSD friction modifier.

There are people on the forums that say you will destroy your LSD if you run it without friction modifier. However, others have stated (and I believe Redline themselves say) that the friction modifier lowers the lock up and just makes the diff quieter, probably chatter in low speed parking lot type situations.

I would prefer higher lockup, and am not concerned about noise because racecar. Can I just run the 75w90NS or 75w140NS without the friction modifier in my LSD?

[e30 gangsta]

Ring up redline they will tell you. All my cars run 75/140 with the modifier though. Honestly if you are looking for more lockup just add a plate. You can even do 4 plates if you machine parts of the lsd.

[ForcedFirebird]

You are correct about the chatter. That's because you are causing more friction between the plates, which *will* give you slightly better grip, but at a severe reduction in duty life. To me, the wear/grip ratio is not worth it. We run 75/90 Redline in all the MW and MB diffs, no need to add more modifier, but it also isn't going to hurt anything. As Gangsta said, add your grip with additional clutches, or change the ramp rate for earlier lock.

[agent]

As Gangsta said, add your grip with additional clutches, or change the ramp rate for earlier lock.

Yep.

[e30_302]

Motul 75/140 right out of the bottle for me.

[autox320]

As mentioned already add a clutch.

http://bimmerdiffs.com/collections/188mm-standard-service-parts/products/bimmerdiffs-188mm-3-clutch-kit?variant=10307852999

Running a 188 4.45 3-clutch. Usually using Amsoil severe gear 75-90. If heat is an issue can move to 140 weight, Just depends on how much your diff is puking vs how long running it hard.

Modifiers can be bad and cause more slip, less lockup, which generates more heat which can mean puking. Trade offs. Could overheat and wear out the clutches faster.

A good 3puk setup will last longer than OEM just due to less heat made. Best of all the power is seemingly to the ground.

[Wh33lhop]

Slapping in an extra clutch pack is super straightforward. Put some 75W140LS in it and you're good--I doubt you'll need anything more unless you are running slicks and crazy power.

[Emre]

I've been running Amsoil Severe Gear 75-140 for years. Both in my E30 and 190E Cosworth. Never added friction modifiers. Diffs have lasted years, even with race suspensions, R-comp tires, and a relatively "slidey" driving style.

[moatilliatta]

Redline 75w110