# Fourth-gear clutch piston stroke (SB4A-EL 4AT)

Canonical URL: https://miatatorque.com/spec/4gr-clutch-piston-stroke-sb4a/

Applicability: NB 2001–2005 (BP-Z3, 4AT) — 2003–2005 factory references identify this component manual; 2001–2002 inferred within NB2 non-turbo family.

Confidence: fsm

Air pressure
390 kPa max.
Piston stroke
1.77—2.58 mm

Always confirm against your factory manual. Match every restriction and follow all stages and procedure notes. Disputed claims must not be automatically resolved. The complete record below preserves every printed unit, source claim and procedure.

```json
{
  "id": "4gr-clutch-piston-stroke-sb4a",
  "name": "Fourth-gear clutch piston stroke (SB4A-EL 4AT)",
  "aliases": [],
  "applies_to": [
    {
      "gen": "NB",
      "years": [
        2001,
        2005
      ],
      "engines": [
        "BP-Z3"
      ],
      "trans": [
        "4AT"
      ],
      "note": "2003–2005 factory references identify this component manual; 2001–2002 inferred within NB2 non-turbo family."
    }
  ],
  "kind": "non-torque",
  "value_text": "Air pressure\n390 kPa max.\nPiston stroke\n1.77—2.58 mm",
  "procedure": {
    "notes": "Use a dial indicator while applying and releasing compressed air through the indicated assembly passage. Maximum 390 kPa {4.0 kgf/cm²,57 psi}. Never apply compressed air longer than 3 seconds at a time; the manual warns this damages the seal. Remove 4 GR planetary gear component first (PDF 62). Pack has 1 drive/1 driven plate. Procedure and table metric agree; printed inch endpoints differ."
  },
  "confidence": "fsm",
  "sources": [
    {
      "source": "workshop-sb4a-el",
      "page": "05–13Y–51 (PDF p. 63)",
      "as_printed": "Air pressure\n390 kPa {4.0 kgf/cm², 57 psi} max.\nPiston stroke\n1.77—2.58 mm {0.07—0.101 in}",
      "verified_years": [
        2003,
        2005
      ],
      "document": {
        "id": "workshop-sb4a-el",
        "tier": 1,
        "title": "Mazda SB4A-EL Automatic Transmission Workshop Manual",
        "part_number": "9999-95-422H-99",
        "covers": [
          {
            "gen": "NB",
            "years": [
              2003,
              2005
            ],
            "engines": [
              "BP-Z3"
            ],
            "trans": [
              "4AT"
            ]
          }
        ],
        "note": "The 2003 (PDF p. 1234), 2004 (PDF p. 1254) and 2005 (PDF p. 1388) MX-5 manuals explicitly reference part 9999-95-422H-99; the supplied copies are identical to the previously audited component manual."
      }
    },
    {
      "source": "workshop-sb4a-el",
      "page": "05–50–1 (PDF p. 87)",
      "as_printed": "4GR clutch\nNumber of drive/driven plates 1/1\n4GR clutch clearance (mm {in}) 1.77—2.58 {0.07—0.10}",
      "verified_years": [
        2003,
        2005
      ],
      "document": {
        "id": "workshop-sb4a-el",
        "tier": 1,
        "title": "Mazda SB4A-EL Automatic Transmission Workshop Manual",
        "part_number": "9999-95-422H-99",
        "covers": [
          {
            "gen": "NB",
            "years": [
              2003,
              2005
            ],
            "engines": [
              "BP-Z3"
            ],
            "trans": [
              "4AT"
            ]
          }
        ],
        "note": "The 2003 (PDF p. 1234), 2004 (PDF p. 1254) and 2005 (PDF p. 1388) MX-5 manuals explicitly reference part 9999-95-422H-99; the supplied copies are identical to the previously audited component manual."
      }
    }
  ],
  "jobs": [],
  "system": "transmission",
  "component": "inventory-pass-2026-10",
  "componentName": "Service measurements and fasteners",
  "sequence_diagrams": [],
  "url": "https://miatatorque.com/spec/4gr-clutch-piston-stroke-sb4a/"
}
```