# Forward clutch piston stroke (SB4A-EL 4AT)

Canonical URL: https://miatatorque.com/spec/forward-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.
Stroke
1.40—1.60 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": "forward-clutch-piston-stroke-sb4a",
  "name": "Forward 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.\nStroke\n1.40—1.60 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. Install forward clutch to 4 GR case before measuring. Pack has 4 drive/4 driven plates. Procedure and table inch precision differs; metric agrees."
  },
  "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.\nStroke\n1.40—1.60 mm {0.056—0.062 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": "Forward clutch\nNumber of drive/driven plates 4/4\nForward clutch clearance (mm {in}) 1.40—1.60 {0.06—0.07}",
      "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/forward-clutch-piston-stroke-sb4a/"
}
```