Genuine Mazda Rear Differential Adjustment Shim – Various Sizes

Genuine Mazda Selectable Rear Differential Adjustment Shim

Replacement Genuine Mazda rear differential adjustment shim for Mazda MX-5 Mk3, Mk3.5 and Mk3.75 NC models and Mazda RX-8 models listed in the compatibility table.

This is a multi-variant listing containing 19 different shim thicknesses from 5.50mm to 6.50mm. Select the exact thickness required from the product options before ordering. One shim in the selected size is supplied.

The shim is fitted within the rear differential assembly and is used when establishing the specified bearing preload, component position and internal clearance. Its precise thickness allows the differential assembly to be adjusted during inspection, rebuilding or component replacement.

The correct shim cannot be selected from the vehicle model alone. The differential must be dismantled and measured using the applicable Mazda workshop procedure. The required thickness depends on the individual differential casing, bearings, gears and components being assembled.

An incorrect shim thickness can create excessive or insufficient bearing preload, incorrect internal clearance or unsuitable gear positioning. This may result in differential whine, rumbling, overheating, premature bearing wear or damage to the crown wheel and pinion.

• Part type: Rear differential adjustment shim
• Mazda catalogue description: Shim, Adjust
• Primary use: Establishes the specified differential bearing preload and internal component position
• Location: Inside the rear differential assembly
• Product format: One Shopify listing with 19 selectable thickness variants
• Available thicknesses: 5.50mm to 6.50mm
• Quantity required: Depends on the differential specification and measurements taken during assembly
• Quantity supplied: 1 shim in the selected thickness
• Brand: Genuine Mazda
• Variant references: R001-27-355 through R001-27-375, as individually listed in the product options
• Fitment note: Select the required thickness by accurate differential measurement, not by vehicle model alone

Available sizes:

• 5.50mm – R001-27-355
• 5.60mm – R001-27-356
• 5.65mm – R001-27-357
• 5.70mm – R001-27-358
• 5.75mm – R001-27-359
• 5.80mm – R001-27-361
• 5.85mm – R001-27-362
• 5.90mm – R001-27-363
• 5.95mm – R001-27-364
• 6.00mm – R001-27-365
• 6.05mm – R001-27-366
• 6.10mm – R001-27-367
• 6.15mm – R001-27-368
• 6.20mm – R001-27-369
• 6.25mm – R001-27-371
• 6.30mm – R001-27-372
• 6.35mm – R001-27-373
• 6.40mm – R001-27-374
• 6.50mm – R001-27-375

Size selection: Select the exact shim thickness determined during differential measurement and setup. Do not assume that the existing shim size should automatically be reused when bearings, gears, casing components or other internal parts have been replaced.

Fitment advice: These shims are confirmed for the Mazda MX-5 NC and RX-8 rear differential assemblies. Different final-drive ratios, limited-slip differential types and internal component combinations may require different shim arrangements. Confirm the differential specification and calculated thickness before ordering.

Other items to consider: When rebuilding the differential, consider inspecting or replacing the carrier bearings, pinion bearings, oil seals, collapsible spacer where applicable, bearing races, retaining nuts, differential mounting bushes and differential oil.

Useful tools / consumables: Bearing pullers, workshop press, differential case spreader where specified, dial indicator, magnetic stand, micrometer, depth gauge, inch-pound torque wrench, bearing marking compound, assembly lubricant, casing sealant and manufacturer-specified differential oil.

Difficulty guide: DIY Difficulty: Advanced. Correct installation requires removal and dismantling of the differential, accurate measurement of bearing preload and internal clearances, and specialist knowledge of differential setup. Installation by an experienced transmission or differential specialist is recommended.

Why Genuine Mazda? Genuine Mazda differential shims are manufactured in accurately controlled thicknesses to match the original differential casing, bearings and gear assembly. Correct dimensional accuracy and material specification are essential for achieving the required preload, alignment and reliable differential operation.

What’s in the box: One Genuine Mazda rear differential adjustment shim in the thickness selected from the product options.

Installation notes: Measure the differential assembly using the applicable Mazda workshop procedure before selecting the shim. Install new bearing races fully into their seats, keep all mating surfaces clean and verify bearing preload, backlash and gear-tooth contact after assembly. Do not operate the differential until all measurements are within specification and the unit has been filled with the correct differential oil.