Mini 4WD Gear Set Compatibility Guide
"Will this gear set fit my chassis?" is a physical question, separate from "which ratio should I run?" This article answers only the first one: which gearbox cover and gear-set part number actually closes cleanly on which Tamiya Mini 4WD chassis code. If you already know your chassis and want help choosing between the ratios a set offers, see the gears guide and gear ratio chart instead; for pairing a ratio to a specific motor's power band, see motor and gear matching. Here, the only question is fitment.
Two gear families that do not cross over
Tamiya's current Mini 4WD range splits into two drivetrain families, and a gear set from one family will not close into the other's gearbox. Double-shaft (Mini 4WD PRO) chassis — MS, MA and ME — carry the motor at midship and drive all four wheels directly through a two-piece gear case with no separate propeller shaft. Single-shaft (standard) chassis — the rear-motor family (AR, VZ, VS, Super-II, Super X, Super XX, Super TZ, Super TZ-X, Zero, Type 2/4/5) and the front-motor family (FM, FM-A, Super FM) — drive through a separate prop shaft to a rear or front gearbox. A PRO gear set is stamped "for MA & MS Chassis" (and covers ME) on the box; a standard gear set names the rear- or front-motor chassis it fits. Buying by ratio number alone, without checking this split first, is the single most common fitment mistake.
Gear sets by chassis code
The table below lists official Tamiya gear-set part numbers and exactly which chassis codes each one is sold for, based on the product listings and the official chassis compatibility catalogue.
| Gear set | Item # | Ratio(s) | Fits |
|---|---|---|---|
| Mini 4WD PRO High Speed Gear Set | 15355 | 4:1 | MS, MA, ME (PRO double-shaft only) |
| Mini 4WD PRO Super Speed Gear Set | 15349 | 3.5:1 | MS, MA, ME — small-diameter tyres recommended |
| Mini 4WD PRO High Speed EX Gear Set | 15429 | 3.7:1 | MS, MA, ME |
| Mini 4WD PRO Gear Bearing Set | 15347 | — | MS, MA, ME (bearing upgrade, not a ratio change) |
| Setting Gear Set (for AR Chassis) | 15456 | 3.5:1 / 3.7:1 / 4:1 / 4.2:1 / 5:1 | AR, Super-II, VS, VZ — includes a 1.4mm hollow prop shaft and 620 bearing |
| High Speed Counter Gear Set | 15236 | 4:1 / 4.2:1 | AR, VS, Super-1, Super-II, Super X, Super XX, Super TZ, Super TZ-X, Zero, Type 2/4/5, FM, FM-A, Super FM — not VZ |
| High Speed EX Counter Gear Set | 15434 | 3.7:1 | AR, VZ, FM-A |
Two things stand out for fitment specifically. First, VZ appears in the AR-branded 15456 set and is also listed on Tamiya's product page for the 15434 High Speed EX Counter Gear Set, but it is absent from the older 15236 set — a VZ-chassis car built with the 15236 will not seat correctly. Second, 15236 spans both rear-motor and front-motor chassis codes despite their different motor positions, because it is the counter-gear stage of the drivetrain, not the prop-shaft length, that the set replaces; Tamiya supplies "two types of counter gear shaft" in that box specifically so it can serve chassis with different shaft geometry under one part number.
Why the gearbox cover itself is the real fit check
A gear set's teeth can be the correct pitch and still not close, because the gearbox cover — the plastic case the gears sit inside — is chassis-specific. MS splits into three separate units (nose, centre and tail), each with its own small gear cover, so a gear swap on MS means reseating three covers squarely, not one. AR, VZ and the other single-shaft chassis instead use one rear (or front, for FM-A/FM/Super FM) gearbox case that the whole counter-gear-and-spur-gear stack drops into before the cover snaps shut. If the cover does not sit flush without being forced, the fit is wrong — a strained cover on a spinning gear train is a durability problem before it is anything else. Confirm your exact chassis code against the official chassis and compatible parts catalogue before ordering, since a kit's box art alone does not always make the chassis code obvious.
Chassis that do not take a swappable gear set at all
Not every current Tamiya chassis accepts an aftermarket gear set. The FUN-VROOM EZ Chassis (item 19024) is a snap-assembly, single-AA-cell platform built for young or first-time builders: its gears sit directly in the chassis frame under a snap-fit cover at a fixed 50:1 ratio, and it is not designed around the interchangeable gear-set system described above. Treat EZ Chassis kits as a separate product line for fitment purposes, not as a variant of AR, VZ or MS.
Frequently asked questions
Can I put a PRO gear set (15355, 15349, 15429) into a VZ or AR chassis?
No. PRO gear sets are cut for the double-shaft MS/MA/ME gear case and driveline, which has no propeller shaft. VZ and AR are single-shaft chassis that need 15456 or 15434 instead (15236 also fits AR but is not listed for VZ) — the tooth pitch and case shape are different, not just the ratio.
My VZ car's gearbox cover won't close with a counter gear set I already own — why?
Check the part number against the table above. The older 15236 counter gear set is not listed for VZ — the 15434 High Speed EX set is — but the safest pick is the AR-branded 15456 Setting Gear Set, which was specifically extended to cover VZ, Super-II, VS and AR.
Does a compatible gear set guarantee it's race-legal?
No — fitment and rule legality are separate checks. Confirm ratio, dimension and modification limits against the official Mini 4WD race regulations and Stock Class rules; on-day technical inspection and the organiser's decision take precedence over any chart, including this one.
Checklist before you buy a gear set
- Identify your exact chassis code (MS/MA/ME vs AR/VZ/VS/Super-series vs FM/FM-A/Super FM) from the instruction sheet, not the body name.
- Match that code against the "Fits" column above, or the current listing at the official chassis compatibility list guide, before ordering by ratio alone.
- For MS specifically, remember three separate covers (nose/centre/tail) need reseating — see the MS chassis compatibility notes.
- For VZ builds, double-check you have 15456 — or the 15434 EX set — and not an older 15236 counter gear set — see the VZ chassis compatibility notes.
- After fitting, spin the wheels by hand before adding a motor: a cover that needed force to close is a fitment failure, not a break-in issue.
- Confirm ratio and modification legality separately against current event rules before race day.