2025 GMC Sierra 3500 HD Crossover Toolboxes
A crossover toolbox (Weather Guard® calls theirs a saddle box) spans the bed rails right behind the cab, so your tools stay locked up while the bed floor stays open for cargo. This page shows the crossover and saddle boxes from Weather Guard® and TrailFX that are listed to fit the 2025 GMC Sierra 3500 HD.
Fitment notes for the 2025 Sierra 3500 HD
- Generation: the 2025 Sierra 3500 HD belongs to the current GM heavy-duty generation (2020 and newer), which was refreshed for 2024.
- Beds: manufacturer fitment data for this truck covers the standard (6 ft. 10.2 in.) and long (8 ft. 2.2 in.) beds. A crossover box sits on the bed rails, so bed width matters more than length, but not every box is listed for every bed. Each product page lists the beds it is made for.
- Style Side beds: these boxes are made for pickup beds, not cab and chassis trucks. Always measure your bed to confirm fit.
How to choose
- Profile: low profile boxes sit closer to the bed rails and keep more of your rear view; standard boxes hold more; deep boxes drop farther into the bed for the most room (for example 15 cu. ft. on the Weather Guard® 123 series).
- Size: extra wide boxes (such as the 15.5 cu. ft. Weather Guard® 117 series) hold more than standard boxes (11 cu. ft. on the Weather Guard® 127 series).
- Aluminum or steel: aluminum is lighter and won't rust; steel boxes are heavier and very tough. Both come in several finishes.
- Lid and lock: check each listing for the lid style and lock. For example, the Weather Guard® 123 series has a single lid and the 1KEY ULTRALOCK, so one key can work across your Weather Guard® boxes.
Shop all GMC Sierra 3500 HD parts, all 2025 GMC Sierra 3500 HD parts, all GMC Sierra 3500 HD toolboxes, all crossover toolboxes or every truck toolbox we carry. Not sure which style you need? Read Crossover toolbox vs side mount toolbox and What size truck toolbox do I need? For more ideas, read our Silverado HD and Sierra HD accessories guide.
2025 Sierra 3500 HD Crossover Toolbox FAQ
Can I use a crossover toolbox with a tonneau cover on my 2025 Sierra 3500 HD?
Most standard tonneau covers need the front of the bed rails, where a crossover box sits. A tool box tonneau cover is made to work with a crossover box, so check that page and the cover's fitment notes.
How does a crossover box install?
Mounting hardware and method vary by box and truck, so read each product's installation and fitment notes before you buy.
Will a crossover box block my rear window?
A low profile box sits lowest on the rails, so it blocks the least of your rear view. Compare each box's height in its listing.