First off, I am under the assumpton that the S5 viscious LSD will go into the S4 diff housing with no trouble. Correct?

I have a used LSD coming to me sometime this month. I'm trying to put together a parts list of the seals and bearings and such that I need to order to go with it. I'm also changing the ring and pinion most likely. All used parts.

So, from mazdatrix http://mazdatrix.com/g7.htm :
- Pinion seal
- Front pinion bearing 2 Required (2)
- Collapsing sleeve/collar
- Middle pinion bearing
- Rear pinion bearing
- Side axle seal (2)
- Rear trans seal
The LSD has carrier bearings and the races on it with about 25,000mi on it.

Anything else?
Thanks.

 

You will probably need new spacers/washers to set the pinion depth too, but you won't know what size until you have already half assembled the unit.

 

Would those be fairly universal? As in, can I get those locally from a shop or would I have to order those too?

 

Sorry to break it to you, but you don't want an OEM S5 LSD. They're non-rebuildable and contrary to what some might like to think, they do "wear out" so to speak. The fluid internal to the diff is very special and it breaks down over time and with hard use. The effect of this is that the diff won't limit slip very well and it'll have delayed locking characteristics, which can cause strange handling.

A much better choice would be a rebuilt (key word) S4 LSD, or if it's an NA, then a Miata Torsen, or if it's a TII, an FD Torsen are also good choices depending on the intended use. Any of these will bolt right into your housing (keeping in mind that you can't mix and match the different size stuff between TII and NA).

 

The spacers are available from Mazdatrix. RacingBeat has some of the same pieces but some are cheaper( side bearings for instance).