Mercedes A Class Rear Cover Tray Undertray A1776900303

Part number A1776900303. We take parts off vehicles every week, and this page is updated with a link straight to the part as soon as another one arrives.

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About part number A1776900303

A rear cover tray, also known as a rear undertray, is a protective panel fitted beneath the underside of the vehicle. It forms part of the bodywork and underbody protection system, mounting directly to the chassis and surrounding floorpan area. This panel shields mechanical and structural components from water, stone impacts, mud, and road salt, while helping to smooth airflow under the car to reduce drag and road noise when driving.

To confirm that this part is correct for your vehicle, you must check that your existing panel displays the part number A1776900303. On plastic underbody trays, this number is typically stamped or moulded directly into the plastic on the upper or lower surface. Matching the part number exactly is the only way to ensure the part will fit correctly, as physical dimensions and mounting points vary across different versions.

Undertrays are usually replaced because they have become cracked, scraped, or torn from hitting high kerbs, speed ramps, or road debris. When replacing this panel, you will often need new fixings such as plastic trim clips, screws, or speed nuts, as the original fasteners frequently break, rust, or go missing when the old tray is removed.

About this kind of part: wheel arch liners

A wheel arch liner is the moulded plastic or felted shell inside a wheel arch that keeps water, salt and stones off the inner wing, the suspension and the wiring. It is hidden and it is not structural, but it is the part that decides whether the metal behind it rusts, so a missing or torn liner is a slow problem rather than a cosmetic one. Mudflaps, undertrays and the air ducts that feed the brakes are the same kind of part doing the same job elsewhere under the car.

Why people replace one

  • The liner has torn away from its clips, usually after a wheel has picked it up at speed, and it now rubs the tyre.
  • Road debris or a kerb has split the liner along an edge.
  • The clips and screws have rusted away or pulled through, so the liner hangs down and catches.
  • The liner was removed for a repair and never refitted, which leaves the inner wing exposed.
  • A felted liner has become waterlogged and heavy and has pulled itself off its fixings.

Fitting it

  • The wheel normally has to come off, and the car must be supported properly on axle stands rather than a jack alone.
  • A liner is held by a mixture of plastic screws, clips and expanding rivets around its edge, and most of them break on removal, so a set of fixings is worth having before starting.
  • Fit the fixings loosely around the whole edge first and tighten them afterwards, otherwise the last few holes will not line up.
  • With the liner out, it is worth looking at the metal behind it. A liner that has been missing for a while has usually exposed something worth seeing.

Making sure it is the right one

  • Match the part number moulded into the liner. Front and rear differ, the two sides differ, and a model with wider arches takes a different part again.
  • Count the fixing holes and compare their positions with the old liner. This is the quickest way to tell two similar liners apart.
  • Check whether yours has cut-outs or ducts for brake cooling, a sensor or a washer line. These vary by specification.
  • Compare the material. The same position is made as hard plastic on one version and as a felted shell on another, and they use different fixings.

What to look for in the photographs

A Part number — Moulded into the inner face. It is often the only difference between two liners that look the same.
B Fixing holes — The holes, slots and rivet points around the edge. Count them and compare the spacing with your own liner.
C Cut-outs and ducts — Any opening for brake cooling, a sensor or a washer line. These vary by specification and are part of the match.
D Edge condition — Look along the whole rim, particularly where the fixings pass through. This is where a liner tears out.
E Material — Hard plastic or a felted shell. They are not interchangeable and they take different fixings.

This section describes wheel arch liners parts in general. The numbers and the photographs above are this part.

Free next-day delivery in the United Kingdom Sent with DPD on a tracked, next-day service. Most mainland addresses are next day; the Highlands and Islands, Northern Ireland, the Channel Islands and the Isle of Man can take a day longer.

Returns Thirty days to change your mind, and we pay the return postage in the United Kingdom and Germany.

Trade and VAT C.E.J Haime Group Limited is VAT registered in England and Wales, and every order comes with a full VAT invoice.

Not sure it is the right part? Send us your registration or VIN and we will check this part number against your own vehicle before you buy.

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