19 Sep
Every 4WD owner has gone through this situation: When you load up the ute tray to organise your stuff but face a mess instead. On every turn your gear is sliding, tools clinking around, & straps buried under a mountain of heavy gear.
If you can relate to it then hear out. An under tray tool box can solve your problem. It keeps your essential tools safe, organised, weather-proof, and out of the way.
But there is another thing too, a bit of technical detail. You need to get the under tray tool box measurement and fitment right. Otherwise, it can end up scraping on speed bumps, blocking your suspension travel, & risking your safety.
At Perth 4WD, we’ve fitted more trays and tool boxes than we can count.
From tough Glennic steel trays built in Perth to Paramount tool boxes, we’ve dealt with it all. So, we know how a professional install differs from an ordinary one. Hence, we prepared under tray tool box installation guide for you.
Let’s get started.
Importance of Under Tray Tool Box Measurement
An under tray toolbox is a storage box mounted beneath the tray or well of your ute. It gives you extra secure space for tools, recovery gear, straps, etc., without using up tray floor space.
Proper under tray tool box fitment is required to:
- Avoid contact & damage to exhaust pipes, mufflers, catalytic converters, shocks, sway bars, wiring, brake lines, fuel tanks, chassis rails.
- Maintain proper ground clearance even when fully loaded & avoid scraping & dents when going up steep driveways, over speed-bumps, or off-road.
- Helps in weight distribution and prevent shifts in centre of gravity so your ute doesn’t overload any part of chassis & reduce the load of springs.
- Improve durability and prevent rattling, fatigue, & corrosion of vehicle.
So, let’s guide you in ute under tray toolbox fitting.
What Tools & Data You’ll Need?
To get your measuring for underbody tool box accurate, gather these:
| Tool | Purpose |
| Measuring Tape / Ruler | For checking width, height, and depth |
| Spirit Level | To level the toolbox |
| Screwdriver or Drill with Bits | For drilling pilot holes and securing bolts |
| Wrench or Socket Set | To tighten bolts, nuts, and hardware |
| Pencil / Marker / Chalk | To mark bracket positions |
| Safety Gloves and Goggles | Protects hands and eyes during process |
| Vehicle Manual | For payload & specs of vehicle |
You should also have a know-how of vehicle data, existing component info and other conditions, e.g.
- Position of exhaust, heat shields, wiring looms, fuel lines
- Bracket mounting points already present
- Tray height
- Chassis dimensions, rail width & distance between rails
- Ground clearance
- Suspension travel
- knowledge of local roads (how rough)
- Load expectancy and off-roading frequency
Key Dimensions to Measure
Once you’ve gathered all the tools and noted all the required data, it’s time for action. Find the following precise dimensions for proper under tray tool box measurement.
| Dimension | What to Measure | Values / Margins to Leave | Why It’s Important |
| Height under tray | From underside of tray (or bottom of existing tray floor) to lowest point of chassis/exhaust and to ground when loaded | Leave at least 150 mm (more if you’re off-road) clearance to ground under load.
Also allow extra for brackets + box base thickness. |
Prevents scraping, enables clearance over obstacles. |
| Width available | Distance between chassis rails
Distance from outer rail to tray edge Width of space under tray not obstructed by brackets |
Allow for some margin so box doesn’t catch on tray edges or protrusions
Leave 10-20 mm clearance on each side |
Fit it without modifying rails or tray. |
| Depth / Length of box (front-to-rear) | From front mounting bracket/back of tray to wheel arch, exhaust or other obstruction | Box must not impede suspension or exhaust movement
Leave some space for movement and heat |
Avoid damage and facilitate installation & maintenance. |
| Bracket height and mounting allowance | Height and space for under tray toolbox mount brackets
Space for lid opening |
Consider bracket thickness
Leave extra so bolts and nuts clear frameLid swing shouldn’t hit ground or tray sides |
For safe mount and functionality. |
Not just rely on your memory. Note down all these values and keep them along when selecting your tool box.
Choosing the Right Under Tray Toolbox Size & Style
Okay, now it’s time to apply those dimensions you’ve taken and choose an under tool box. However, you’ll need to make several other choices too. E.g.
-
Full-length vs half-length under tray boxes:
Full boxes give maximum capacity but can interfere with spare tyre or access to underside. While half-length leave more room for jack/tow access.
-
Single lid / dual door designs:
Single lid takes less space & is easier to manage. Dual lids or doors can increase access but may need more clearance. Hence, set the hinge positions wisely.
-
Material choice (Steel vs Aluminium):
Steel is heavier and thicker welded, which means more bracket strength and more clearance underneath. Aluminium is lighter and thinner but flex more under load.
-
Locking, sealing & weatherproofing:
Get seal designs, locks, and lids that shed water, prevent corrosion and keep tools dry. But keep in mind that sealing, gasketing, lip dims add to overall size. Also, proper finish and galvanising or powder coating is also required to cope up with Aussie conditions.
Now, if you’ve selected a tool box, move ahead.
Fitting / Mounting Considerations
Remember the following to get the tool box fit under tray clearance and maximum functionality out of it.
| Consideration | Details |
| Choice of Bracket types | Choose between welded brackets, bolt-on sub frames, and channel mounts. |
| Measuring height under tray | Keep it high enough to maintain ground clearance, but low enough for accessibility. |
| Level mounting an under tray tool box | Avoid front-to-back slope (causes water pooling) and side tilt (makes lid harder to operate). |
| Bolts, spacers, washers, lock nuts | Use stainless hardware. Washers spread load, lock nuts or thread lock prevent vibration loosening. |
| Avoid weak/dangerous zones | Never drill near wiring, fuel, or brake lines. Avoid structural stress points. Always check behind the frame before drilling. |
| Load Capacity of Frame/Rails | Rails must handle box weight + tools + vibrations. Reinforce if rails are light or already stressed. |
Keeping all of them in mind, start the actual process.
How to Measure for Under Tray Toolbox: 8 Steps
Let’s suggest you the precise & correct way to fit under tray tool box. So, it can stay secure and save you regrets later.
1. Measure all required dimensions
Use tape to measure height under tray (with load), width between rails and from tray edges, depth front-to-rear, and bracket mounting space.
2. Select a toolbox that fits within those measurements with some margin
Pick box size slightly less than maximum space (allow margin for fit and vibration).
3. Position the toolbox under the tray to test fit before drilling
Rack it in with brackets (un-bolted or loosely held) to check lid opening, ground clearance, and distance from exhaust/suspension.
4. Mark mounting holes on frame/tray
Use the toolbox bracket as template and mark accordingly. Double check the marks and make sure holes don’t hit wiring etc.
5. Drill pilot holes carefully & protect wiring/fuel lines
Use smaller pilot for a safe process and check alignment. Then use rust-inhibitor after drilling to soften the edges.
6. Attach brackets and then the toolbox
Use the correct bolts, hardware, lock nuts and apply torque as needed. Distribute the load evenly and double check the connections.
7. Check alignment, level, proper clearance
With the box installed, open lid, test full range of motion. Then check clearance over road bumps or off-road to make sure nothing rubs.
8. Secure all bolts, test lid/opening, test for movement
Do the shake test, drive around, and hear for rattling sounds or scrapping marks. Also perform waterproof test if possible.
Common Mistakes & How to Avoid Them
Now, let’s talk about the common pits that trap most of the people during fitting.
| Mistake | Why to Avoid it |
| Not checking exhaust or suspension | A box too close to moving parts will hit on bumpy roads |
| Measuring only the tray floor | bracket/base thickness or lid hinge space will miss out |
| Using weak brackets or bolts | cheap hardware will fail under load or vibration |
| Poor alignment | lid hits other parts or water pools, leading to rust or leaks |
| Overloading beyond design capacity | box + tools + gear plus hitting bumps will exceed what rails or box base can take |
| Assuming all trucks are the same | Every tray differs in height, width, exhaust routing and ground clearance |
So, you’ve installed your tool box? The work is not done yet.
Safety & Maintenance Post Fit
Once fitted, arrange the timely maintenance of your toolbox. It will keep it working well and stay safe. Make sure to:
- Check bolts & brackets regularly after few thousand km or off-road trips.
- Inspect for rust / corrosion especially around holes, base, hinge areas if using steel.
- Clean debris or mud around seals and lids to keep them weather-proof.
- Watch for rattling or shifting as it indicates loose hardware or fatigue.
- Clean inside & outside regularly to prevent buildup of moisture or road grime.
Want to get expert toolbox installation Perth?
Let Perth 4WD Fit Your Toolbox Like a Pro
We supply quality Glennic trays and offer safe installation under tray toolbox. Our team measures, mounts, and seals everything properly so, it well works for long time and keep your gear organised.
If you need expert fitment or help picking the right under tray toolbox sizes for your ute
FAQs
1. Can I fit any under tray toolbox to any vehicle?
No. Each vehicle is different. You must check measuring width for tool box under tray, height, exhaust/suspension layout, and frame strength of your vehicle.
2. How much clearance do I need from the ground?
Rule of thumb: at least 150 mm under load. If you drive off-road, more clearance will protect the tool box and its contents.
3. What size bolt should I use to mount the box?
Stainless steel bolts, of size M8 to M10, with washers and lock nuts. Its thickness depends on bracket and material you’re dealing with.
4. Will fitting a toolbox affect my vehicle warranty?
Usually, no, if the box, bracket, and hardware do not damage or modify structural or safety critical components. You can also confirm it from your vehicle’s manufacturer.
5. How to avoid water entering the box during rain?
Make sure the lid is level (front-to-rear), use quality weather seals / gaskets, have lid lips that deflect water out, and avoid low mounting to avoid water splashes.