BMW Z3 1.9 (1996) – R345V differential: LSD or open?

Diede

Diede

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Apr 7, 2026
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Hi everyone,

I’m trying to figure out which differential I have in my BMW Z3 1.9 (1996) and I’m getting a bit lost. According to my VIN/options, I have S209A (25% limited slip differential), so that should mean it’s an LSD. However, the tag on my differential says R345V1721, which confuses me.

From what I found:
  • 3.45 = gear ratio
  • V might indicate a viscous type?
  • R might mean “Rutschsicher” (non-slip)
What makes it more confusing is how it behaves:
  • When I put it in 1st gear and turn one wheel, the other wheel turns in the opposite direction
  • When the car is in neutral and I turn one wheel, the driveshaft turns
This makes it look like an open differential. But I’ve read that some LSDs only lock under load, so they can behave like an open diff when tested in the air.

So I’m not sure what to conclude.
 
Torsen LSD's act like a standard diff until one wheel spins which is when it locks up.

The old clutch type LSD's have an S in front of the ratio number, so S345.

You need to remove the rear cover and take a pic of the differential itself.
 
You can also see through the fill plug hole using an endoscope. Somewhere on this forum there in an image that shows what each diff looks like
 
Make sure you get new crush washers for drain/ fill plugs. I also think you will have to drain the oil to see, it will probably do it good being changed anyway as they are rarely done.
 
I contacted BMW and they confirmed that my car does have an LSD, specifically a plate-type (clutch) LSD without preload. According to them, this means that when there is no load, it behaves like an open differential. Only when you apply throttle or put the drivetrain under load, the clutch pack engages and it starts to lock.

So the behavior I’m seeing with the car in the air (wheels spinning in opposite directions) is apparently normal for this type of differential.
 
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