Transmission Fluid Leaks After Replacement
Leaks after a transmission swap usually come from pan gasket, cooler lines, or seals — not porosity. Photo the leak before cleanup and verify ATF level.
Quick Answer
**Transmission fluid leaks after replacement** usually come from **pan gasket seating**, **cooler line O-rings or fittings**, **input or output seals**, or **overfill** — not random internal porosity. **Photograph the leak path and fluid level before cleanup** (INV-09), identify **ATF spec**, top off only if safe for a short test, and contact support with photos **before** removing the unit.
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What Does This Article Cover?
- **Pan vs cooler vs front seal** — how to tell them apart
- What to do **before wiping or pressure-washing**
- **Diagnosis table** by leak location
- **Before filing a claim** photo checklist
- When a leak causes **slip or no-shift** (sibling symptoms)
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Where Do Post-Install Leaks Usually Start?
| Location | What you see | Common install cause | |----------|--------------|----------------------| | **Pan** | Puddle under trans, pan wet | Gasket, bolt torque pattern, warped pan | | **Cooler lines** | Fluid at radiator or nut | Reused O-ring, cross-thread, reversed line | | **Front / converter area** | Wet between engine and trans | Converter seal, front pump gasket | | **Tail housing** | Rear drip | Output seal, yoke damage on R&R | | **Fill tube / sensors** | Top seep | Loose sensor, missing O-ring |
Early-mile leak volume: transmission leaks in the first 500 miles: /blog/transmission-leaks-first-500-miles-after-install.
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What Should You Do Before Cleanup?
1. **Photo** wide shot + close-up of wet path — **before wiping** 2. Note **dipstick level** and ATF color 3. Identify **correct ATF spec** used at install 4. Record **odometer** and miles since install 5. If active drip, capture **drip rate** on cardboard 6. Do **not** remove trans to “find leak” internally without guidance — pre-authorization: /blog/pre-authorization-before-removing-unit
Low fluid quickly causes slip and shudder: /blog/transmission-slip-and-shudder-after-replacement or no shift: /blog/reman-transmission-wont-shift-after-install.
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Quick Diagnosis Table
| Leak pattern | Likely source | First action | |--------------|---------------|--------------| | Overnight puddle, pan wet | Pan gasket | Photo, verify torque sequence | | Only when hot, at cooler | Line / O-ring | Photo hot, inspect routing | | Front after drive | Converter / input seal | Photo front area | | After 500+ mi | Heat-cycle seal | See first 3,000 mi checklist: /blog/first-3000-miles-after-reman-transmission-install |
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Before Filing a Claim
| Item | Required | |------|----------| | Leak photos (before cleanup) | Yes | | Fluid level / color note | Yes | | ATF type receipt | Yes | | Odometer photo | Yes | | Scan report (if slip/CEL) | If applicable |
> Before any unit is removed or replaced, document the symptom, save scan results or inspection notes, and contact support with the installation details so the issue can be reviewed accurately.
Full list: required documents for a warranty claim: /blog/documents-required-warranty-claim.
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FAQ
Is a leak always a bad reman transmission?
No. **Gasket, line, and seal** issues are common after R&R — many are correctable without condemning the unit.
Why photo before cleanup?
Warranty review uses **location and pattern** — cleanup destroys evidence (INV-09).
Can I keep driving with a small leak?
**Low fluid** causes slip and heat damage quickly. Level-check; contact support if level drops.
Pan leak vs converter leak?
**Pan:** bottom of trans, often overnight puddle. **Converter/front:** wet between engine and trans after driving.
--- ## WP-AC · INV verified
P1 · SC-T-LEAK · INV-05 · INV-09 · INV-10 · SME pending · P1 cleanup 2026-06-28
Related on Expedia Parts
- Warranty policy and Expedia Protection: /warranty
- Warranty activation — 14-day rule: /blog/warranty-activation-14-day-rule
- Pre-authorization before removing the unit: /blog/pre-authorization-before-removing-unit
- Documents required for a warranty claim: /blog/documents-required-warranty-claim
- Reman transmission won’t shift after install: /blog/reman-transmission-wont-shift-after-install
- Transmission fluid leaks after replacement: /blog/transmission-fluid-leaks-after-replacement