Hot answers tagged lsd
First, as a fellow NA MX5 owner I would simply replace the diff with a Torsen LSD out of an NA 1.8 MX5 and be done with it. It's the most cost effective swap I'm aware of if you actually do need an LSD. Plus it's a fairly strong LSD anyway so unless you're planning to put silly power through it, it should last. That said, the difference between the LSD ...
You need to find the RPO (Regular Production Options) list on the Service Parts Identification label. Similar to what is pictured below. It will likely be on the spare tire cover or the glove box, but may also be in the door jam or under some other compartment lid. Each on of those three digit number/letters indicates an option the car is equipped with on ...
If you have any doubt at all that the RPO code sticker is accurate (like, maybe someone swapped the rear differential), you can tell an ordinary open diff from an LSD by jacking up the rear end of the car, releasing the parking brake, and turning each rear wheel in turn, leaving the other one free to turn by itself. With an open differential, the opposite ...
As Larry said, look for the RPO codes. The code you are looking for the Limited Slip option is G80. Look here for a list of RPO codes specific to your CTS.
If you have at least one halfshaft available, you can turn one side. If the other side (might need someone to help you look) goes the same way, it's at least a limited-slip.
The 'M's should come with an LSD from the factory, so you should be able to find a used one from a specialist BMW parts supplier. I'd also think that the usual manufacturers of LSD have one that would fit, but they're most likely not cheap.
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