4WD Modification Rules
A 4WD modified to the legal maximum in one state can be non-compliant the moment it crosses a border. Here's how tyre size, suspension lift, roof height and GVM/GCM upgrade rules actually differ across Australia.
What's legal where
Every Australian state and territory modification rule sits on top of the same national baseline — the National Code of Practice (NCOP) and its technical standard VSB14, which covers 16 sections from engines and brakes to suspension, steering, body and fuel systems. Heavy vehicles (over 4.5 tonnes GVM) fall under a separate standard, VSB6.
But states layer their own additional requirements and certification schemes on top — VASS in Victoria, VSCCS in NSW, AVCAIS in Tasmania — and the technical limits themselves differ too. The table below compares them side by side; full detail on each state follows.
A quick summary
Australian Capital Territory - read our full guide →
Applies the National Code of Practice directly without its own separate scheme, generally making it more straightforward. Confirm directly with us or Access Canberra before relying on figures for the ACT.
Northern Territory
NT and WA are the only two jurisdictions where locally certified modifications aren’t automatically recognised nationally under mutual recognition — check before moving a vehicle interstate. Roof height increase is capped at 50mm combined across tyres, suspension and body lift together; GCM upgrades apply to pre-registered vehicles only.
Queensland
Runs its own QCOP framework; modifications are classed Minor/Basic/Complex/Specific, with only complex changes requiring certification by a TMR-Approved Person. Interstate certifications aren’t automatically recognised in Queensland. Roof height allows a 75mm split (50mm suspension + 25mm tyre); GCM upgrades apply to pre-registered vehicles only.
Western Australia
Requires approval in principle before work starts on complex modifications — a more front-loaded process than most states. WA and NT sit outside mutual recognition, so a WA-certified upgrade only holds while the vehicle stays registered there. GCM upgrades apply to pre-registered vehicles only.
South Australia
One of the more flexible states — both GVM and GCM upgrades are approved for already-registered vehicles, not just pre-registered ones. Roof height is capped at 50mm combined, using any mix of tyre, suspension and body lift.
New South Wales
Certification runs through the VSCCS scheme, with a second tier (VSCCS J&P) for heavy vehicle body-fit and towing work. NSW also publishes its own supplementary suspension/ride-height manual on top of VSB14. Roof height allows a 75mm split; GVM/GCM upgrades apply to both pre- and already-registered 300 series vehicles.
Victoria
Uses the VASS scheme — light vehicle approval certificates expire 30 days from issue, so timing between certification and registration matters. Only Victorian-based engineers can hold VASS signatory status. Roof height allows a 75mm split; GVM/GCM upgrades apply to 300 series vehicles, pre- and already-registered.
Tasmania
Runs the AVCAIS scheme plus its own supplementary VMCM manual on top of VSB14. Roof height is capped at 50mm combined; GVM and GCM upgrades are both approved for pre-registered and already-registered vehicles.
Before you modify - checklist
Confirm your vehicle's state of registration — that state's rules apply, not where you live or drive.
Check whether your modification is Minor, Basic or Complex under your state's scheme — this decides if certification is even required.
For Western Australia: get approval in principle before starting any complex modification, not after.
Use an engineer or examiner authorised in your specific state (VASS, VSCCS, RES, AVCAIS etc.) — out-of-state sign-off may not be accepted.
Don't assume an interstate-certified modification transfers automatically — confirm with the destination state first.
Keep all certification paperwork and mod plates — you'll need them at registration, roadworthy, and any insurance claim.
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From the blog
Vehicle modifications by State & Territory - a quick guide
Here is a very quick comparison guide as to what is allowed for some simple and common vehicle modifications around Australia. Note if your vehicle is >4.5 tonnes you have a heavy vehicle and different standards (VSB6) apply.
Northern Territory
Max tyre size increase without engineering
50mm
Max suspension lift without engineering
50mm
Body lift permissible
Yes with engineering
Max roof height increase without engineering
50mm total (tyres+suspension+body lift)
GVM upgrade possible
Yes - pre registered and already registered vehicles
GCM upgrade possible
Yes pre-registered, no for already registered vehicles
Queensland
Max tyre size increase without engineering
50mm
Max suspension lift without engineering
50mm
Body lift permissible
Yes
Max roof height increase without engineering
75mm total (25mm tyres+50mm suspension)
GVM upgrade possible
Yes - pre registered and already registered vehicles
GCM upgrade possible
Yes pre-registered, no for already registered vehicles
Western Australia
Max tyre size increase without engineering
50mm above the largest tyre in your model range
Max suspension lift without engineering
50mm
Body lift permissible
Yes with engineering
Max roof height increase without engineering
50mm total (tyres+suspension+body lift)
GVM upgrade possible
Yes - pre registered and already registered vehicles
GCM upgrade possible
Yes pre-registered, no for already registered vehicles
South Australia
Max tyre size increase without engineering
50mm
Max suspension lift without engineering
50mm
Body lift permissible
Yes with engineering
Max roof height increase without engineering
50mm total (tyres+suspension+body lift)
GVM upgrade possible
Yes - pre registered and already registered vehicles
GCM upgrade possible
Yes pre-registered, and already registered vehicles
Victoria
Max tyre size increase without engineering
50mm
Max suspension lift without engineering
50mm
Body lift permissible
Yes
Max roof height increase without engineering
75mm total (25mm tyres+50mm suspension)
GVM upgrade possible
Yes - pre registered and already registered vehicles
GCM upgrade possible
Yes pre-registered, and already registered vehicles
New South Wales
Max tyre size increase without engineering
50mm
Max suspension lift without engineering
50mm
Body lift permissible
Yes with engineering
Max roof height increase without engineering
75mm total (tyres+suspension+body lift)
GVM upgrade possible
Yes - pre registered and already registered vehicles
GCM upgrade possible
Yes pre-registered, and already registered vehicles
Tasmania
Max tyre size increase without engineering
50mm
Max suspension lift without engineering
50mm
Body lift permissible
Yes
Max roof height increase without engineering
50mm total
GVM upgrade possible
Yes - pre registered and already registered vehicles
GCM upgrade possible
Yes pre-registered, and already registered vehicles
ACT
Max tyre size increase without engineering
50mm
Max suspension lift without engineering
50mm
Body lift permissible
Yes with engineering
Max roof height increase without engineering
75mm total (tyres+suspension+body lift)
GVM upgrade possible
Yes - pre registered and already registered vehicles
GCM upgrade possible
Yes pre-registered, and already registered vehicles