FORD FIESTA MK8 B479 2017-2023 1.0 ECOBOOST LH GEARBOX MOUNT 3820S500MC
FORD FIESTA MK8 B479 2017-2023 1.0 ECOBOOST LH GEARBOX MOUNT 3820S500MC
Part-number-led identification for buyers who want to match the component correctly the first time.
This mount supports and locates the transmission side of the powertrain while its bonded isolator helps control engine/gearbox movement, torque reaction and vibration transfer into the vehicle structure. It is a mechanical mounting component with no electronic control function.
| eBay Item Number | 147507396165 |
|---|---|
| Part Type | Gearbox / transmission mounting bracket and isolator assembly |
| Stamped / Cast Number | 3820-S500MC |
| Cross-Reference MPN | L1BG-7M121-BB |
| Service / Catalogue Ref. | 2406428 - cross-reference only; confirm against VIN / existing part |
| Vehicle Family | Ford Fiesta Mk8 / B479 generation |
| Listing Year Range | 2017-2023 as stated in the source listing title; exact fitment must still be confirmed by stamped part number, engine / gearbox specification and VIN |
| Source Donor Year | 2021 |
| Fuel / Engine Family | 1.0-litre EcoBoost petrol / mild-hybrid applications where the exact mounting number matches |
| Known Engine-Code Examples | M0JB; B7JA / B7JB / B7JC - same-number cross-reference examples, not a blanket fitment promise |
| Transmission | 6-speed manual in verified same-number applications |
| Placement | Front-left / nearside / UK passenger-side gearbox mounting position; upper transmission support |
| Material | Aluminium structural mounting body with rubber / elastomer isolation element and steel fixing hardware |
| Finish | Natural cast-alloy appearance with black isolation material; normal cosmetic storage / service marks may be present |
| Included | The mount assembly shown in the listing photographs. Additional bolts / hardware are included only where pictured. |
| Warranty | 30-day seller warranty, subject to the listing terms and statutory rights |
Why Choose a Factory-Production Component?
Designed Around the Vehicle
- Original production geometry and mounting-point layout can reduce fitment uncertainty when the stamped number matches.
- Correct mount stiffness and isolator design are important to powertrain alignment, torque reaction and cabin vibration control.
- Reusing a sound factory-production part avoids gambling on an unknown low-cost pattern alternative whose dimensions or isolator characteristics may differ.
- You receive the photographed component, so you can compare shape, casting and identifiers before purchase.
Fitment Evidence - Part Number First
| Evidence | Vehicle | Engine / Code | Gearbox | Position | Number | Status |
|---|---|---|---|---|---|---|
| Source listing | Fiesta, 2021 | Engine not stated in source | Not stated | Front left | 3820-S500MC | Directly verified |
| Same-number compatibility example | Fiesta Mk8, 2021 | 1.0 EcoBoost 125PS; B7JA / B7JB / B7JC | Manual | Front left / N/S | L1BG-7M121-BB | Verified cross-reference |
| Same-number dismantler example | Fiesta generation 2017-on, donor 2021 | 1.0 EcoBoost 95PS; M0JB | 6-speed | Front left | L1BG-7M121-BB | Verified cross-reference |
| Same-number dismantler example | Fiesta generation 2017-on, donor 2022 | 1.0 EcoBoost mHEV 125PS; B7JA / B7JB / B7JC | 6-speed | Front left | L1BG-7M121-BB | Verified cross-reference |
Year range: the source listing states 2017-2023. This range is shown for search and identification purposes, but it must not be treated as blanket compatibility across every engine, gearbox, trim or facelift. Exact-number and VIN confirmation outrank generation year alone.
3-Door Body Reference
5-Door Body Reference
Technical Mounting Position Reference
What This Part Physically Does
The aluminium mounting body provides a structural connection between the transmission-side powertrain assembly and the vehicle mounting structure. The rubber / elastomer isolator allows controlled compliance so normal engine vibration and driveline torque reaction are not transmitted directly into the body shell.
Common signs that justify inspection include excessive vibration, a knock or thud during take-up, visible rubber deterioration, abnormal powertrain movement, or harshness during gear changes. These symptoms can have other causes, so diagnosis should precede replacement.
Will Not Fit / Do Not Assume Compatibility
- Fiesta ST 1.5 EcoBoost: do not treat this as the performance ST 1.5 mount. Same-family listings show K1BY-7M121-AB for the 1.5 ST application; if that is your existing number, this is not the correct match.
- Earlier 1.0 EcoBoost applications: some earlier Mk8 cars are documented with H1BG-7M121-AC / other references rather than L1BG-7M121-BB. Generation and year alone are not enough.
- 1.1 petrol, diesel, automatic or 5-speed variants: not confirmed by the source item. Do not order unless your exact existing number / VIN catalogue confirms the same mounting.
- Facelift vs pre-facelift: exterior appearance does not prove mount compatibility. Verify the powertrain and stamped number.
- Ford Puma cross-use: L1BG-7M121-BB appears on some Puma applications, but that does not make every Puma compatible with this Fiesta listing. Match by VIN and number.
Buyer Matching Checklist
- Stamped / cast number: 3820-S500MC and/or catalogue cross-reference L1BG-7M121-BB.
- Left / nearside / passenger-side mounting position on a UK right-hand-drive vehicle.
- All fixing holes, slotted holes, studs, casting ribs and isolator orientation against the photographs.
- 1.0 EcoBoost engine and 6-speed manual transmission details where applicable.
- VIN-based parts catalogue confirmation if your number is obscured, superseded or different.
Important: buyers are strongly urged to verify fitment against the high-resolution photographs and exact stamped part numbers rather than relying solely on automated compatibility dropdowns or generic model-year assumptions.
Fitting Guide, Tools & Estimated Time
Required Tools / Workshop Equipment
- Vehicle-specific workshop data
- Socket and spanner set
- Ratchet and extensions
- Breaker bar where required
- Calibrated torque wrench
- Trim / battery-tray tools as required
- Engine support bar or suitable powertrain support
- Workshop jack with protective wood block where approved
- Axle stands / approved lift
- Wheel chocks
- Penetrating fluid for corroded fasteners
- PPE: gloves and eye protection
General Replacement Sequence
- Confirm the stamped number, mounting position and replacement geometry before dismantling anything.
- Park on a level surface, secure the vehicle, isolate the ignition and follow the vehicle manufacturer's battery / safety procedure where necessary.
- Raise and support the vehicle only if required for access. Use approved lifting points and stands / a professional lift.
- Remove only the access components required for the mount area, such as intake ducting, battery or battery tray where the specific vehicle procedure calls for it.
- Support the engine / transmission assembly at an approved point using an engine support bar or suitable workshop method. Do not load fragile casings or sumps incorrectly.
- Note the original mount position and fastener locations, then relieve load from the mount before loosening its fixings.
- Remove the old mount and compare it directly with this replacement: number, hole spacing, studs, offset, height and rubber-isolator orientation must agree.
- Install the replacement initially finger-tight, align the powertrain naturally without forcing it, then tighten fasteners in the correct sequence to the vehicle-specific torque specification.
- Refit removed access components, remove the support equipment, inspect nearby wiring / hoses / shift cables and perform a controlled start-up check for abnormal movement or vibration.
- Road-test only after all fasteners and safety items have been checked. If abnormal vibration remains, inspect the remaining mounts and related drivetrain components.
Estimated Labour Planning Matrix
Planning allowance used below: 1.5 labour hours. This is an estimate for budgeting only; seized fixings, access differences and diagnostic work can increase time.
| Estimated Time | £40 / hr | £60 / hr | £80 / hr | £100 / hr |
|---|---|---|---|---|
| 1.5 hours | £60 | £90 | £120 | £150 |
Illustrative labour only; excludes the part, consumables, diagnostics, VAT where applicable and any additional repair work.
Professional Fitting Service
Professional fitting may be available at our repair facility, subject to workshop availability. Please use eBay Messages for pre-sale questions and to ask what fitting option can be offered through the applicable eBay transaction.
Shipping, Address & Worldwide Delivery
Calculated Shipping - No Free-Postage Promise
Buyers pay the shipping fee calculated / displayed at checkout for the selected delivery service. Shipping cost depends on destination, parcel specification and eBay's checkout calculation.
For eligible international destinations, secure tracked delivery is available through eBay's Global Shipping Programme. Eligible markets include many European destinations plus the USA, Australia, Canada and other supported regions. Final availability and charges are shown by eBay at checkout.
VAT Margin Scheme / Global Accounting
Where this item is sold under the VAT Margin Scheme / Global Accounting method for second-hand goods, VAT is accounted for within the dealer's margin and is not shown separately on the sales invoice. There is therefore no separately itemised VAT amount for the buyer to reclaim.
This wording describes the invoice treatment; it does not mean that the seller has no VAT accounting obligation.
Returns - Correct Part Selection Matters
Please verify before ordering. Incorrectly ordered or change-of-mind returns remain subject to the listing's eBay return settings and the buyer's statutory rights.
A deduction is not automatic simply because the wrong variant was ordered. Where an eligible return comes back in a materially different condition - for example fitted, used beyond reasonable inspection, damaged, contaminated, incomplete or missing parts - an eligible seller may make an evidence-based deduction of up to 50% to reflect the actual loss of value under the applicable eBay seller-protection process. Statutory rights remain unaffected.
Avoid unnecessary returns by matching the stamped number and photographs before installation.
Secure Packing & Dispatch
Prepared for the Journey
Components are packed for transport with suitable protective materials and secure outer packaging appropriate to the part. Our aim is simple: the component you selected should arrive protected, identifiable and ready for your final pre-fitment comparison.
With more than 25,000 parts in stock on the shelves, THEPARTPILOT focuses on organised identification, careful handling and efficient dispatch.
How to Find Us / Customer Support
WhatsApp QR for Fitment Help / Appointment Enquiries
Scan the QR code to contact ThePartPilot on WhatsApp for fitment checks, appointments or fitting service availability.
For faster fitment help, send your vehicle registration, VIN if available, and clear photos of your existing part, connector and part number.
WhatsApp QR for Fitment Help / Appointment Enquiries
Scan the QR code to contact ThePartPilot on WhatsApp for fitment checks, appointments or fitting service availability.For faster fitment help, send your vehicle registration, VIN if available, and clear photos of your existing part, connector and part number.
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Reusing serviceable automotive parts helps extend the useful life of components already manufactured, reduces demand for replacement production, avoids unnecessary material waste and supports a more circular automotive economy. Every correctly matched reused part is a practical step toward reducing manufacturing and disposal impacts while supporting a local UK small business. Thank you for giving a quality component another working life. 💚♻️🇬🇧