If you’re depowering or rebuilding the power steering rack in your NA Miata and want to replace the pinion bearings these are the part numbers, at least for a 1990.
- Upper bearing in the seal at the top of the pinion shaft: 6804
- Lower bearing at the bottom of the pinion shaft: 16001
- Middle bearing inside the pinion shaft: Unsure, mine felt fine after regreasing
For the upper bearing an 11⁄16 socket works great to press it out of the seal housing. You’ll likely damage the rubber seal doing this but you can find a replacement in a rack and pinon seal kit. I used a sealed bearing (6804DD) for additional protection from the elements, but it’s open from factory.
The lower bearing is not press fit and should come out with minimal effort.