SJ Transfer Case Conversion for Suzuki Jimny Gen 3 & Gen 4

If you spend most of your time on technical trails, rock gardens, or towing heavy loads at low speed, you’ve probably found the stock Jimny transfer case… a bit underwhelming.

That’s where the SJ transfer case conversion comes in. Originally fitted to the older SJ413, this transfer case offers massively lower crawl ratios, more torque to the wheels, and a bulletproof chain-free design — making it one of the most sought-after upgrades for hardcore Jimny builds.

1. Gearing Benefits – How the SJ Case Changes Your Jimny

The stock Jimny Gen 3 & Gen 4 transfer case uses a chain-driven 1:4 high range and a mild low range of 2.268:1. This works fine for stock tyres and light off-roading, but once you add 31–35-inch tyres, you’ll feel the gearing strain both on- and off-road.

Key Benefits:

• Huge torque increase in low range – perfect for rock crawling and steep climbs.
• Gear-driven = no chain stretch, stronger under big tyres.
• Ability to tailor high range for on-road drivability or full rock-crawler spec.

2. Installation Overview – Not a Bolt-On Job

The SJ case isn’t a direct fit in a Jimny. You’ll need:

• Adapter Kit – Companies like Protrack.gr, Offroad Armoury, or HM4x4 sell adapter plates and mounts for Gen 3 & Gen 4.
• Custom Propshafts – Different output flanges and lengths require either modified or new shafts.
• Shifter Linkage – Some kits include a new lever, others require custom work.
• Mounting Brackets – The SJ case sits differently in the chassis.

Fitting Steps (Simplified):

1. Remove the stock Jimny transfer case.
2. Install adapter plate/mount kit.
3. Fit SJ case and secure mounts.
4. Connect custom/modified propshafts.
5. Install shifter assembly and check clearance.
6. Fill with oil, test for leaks, and road-test.

Skill Level: High – not recommended for first-time DIY mechanics unless you have fabrication tools. Most people get a 4×4 workshop to handle the swap.

3. Pros & Cons of the SJ Conversion

Pros:

• Massive low range torque increase.
• Stronger than stock chain-driven case.
• Flexible gearing options for different builds.
• Better drivability with big tyres.

Cons:

• More complex install with custom parts.
• Can make highway driving rev-happy if high range is reduced too much.
• Heavier than the stock case.

4. Who Should Do This Conversion?

• Rock crawlers running 33”–35” tyres.
• Overlanders towing heavy trailers who need more control off-road.
• Jimny owners who have maxed out internal reduction gears and still want lower ratios.

Conclusion – The “Next Level” Jimny Mod

For serious off-roaders, the SJ transfer case conversion is one of the most transformative upgrades you can make to a Jimny. It’s not a budget mod and requires proper installation, but the reward is a rock-solid drivetrain that laughs at big tyres, steep climbs, and technical crawling.

If you’re still on 29s or 30s and just want a bit more control, internal reduction gears are the cheaper route. But if you’re building a trail weapon or overland workhorse, the SJ swap turns the Jimny into a whole new machine.