The GDP 4" Portal Gear Lift gives a Polaris RZR XP Turbo S a lift and a gear reduction in one box. The clearance comes from the hub itself, so you can run bigger tires, and the gear reduction gives you the torque to turn them. Because the lift happens at the hub, suspension geometry stays factory and the whole drivetrain sees less stress. Choose a 15% or 30% reduction, cast or billet housings, and single or patented Dual Idler gearing for the most strength available.
Highlights
- 4" of lift at the hubs
- 15% or 30% gear reduction
- Single or Dual Idler gear configuration
- Cast or billet aluminum housings
- Precision-ground 9310 alloy billet steel gears, cool and quiet
- 1.5" diameter 4340 hardened steel drive shaft
- 5/16" advanced steel alloy backing plates, stronger than chromoly
- Universal hubs for 4/156, 4/137, 4/115 and 4/110 bolt patterns
- Dual Idler adds 3/4" front and rear offset (1.5" total extension)
- Optional frame stiffener
- Limited lifetime warranty from the manufacturer
Lift and Gearing in the Hub
A portal box sits at each wheel and drops the axle's output down to a lower hub through a set of gears. That raises the whole machine by 4 inches without changing the A-arm angles, and the gear set reduces the final drive ratio. Since the reduction happens at the very end of the drivetrain, the axles, differential, prop shaft and transmission all carry less load than stock, which helps them last longer even with bigger tires.
What Is a Dual Idler?
A standard portal uses one idler gear between the input and output. The Dual Idler adds a second idler, spreading the load over twice the gear surface for more reliable torque transfer and the strongest gear set you can get. Two idlers only help if they're perfectly matched, so the gears are CNC precision-ground from tough 9310 steel alloy. The Dual Idler setup also adds 3/4 inch of offset front and rear.
Pick Your Gear Reduction
| Reduction | Best for |
|---|---|
| 15% | Trail riders on moderately larger tires who want to keep more top speed |
| 30% | Deep mud and rock gardens, or larger tires that need more torque |
A 30% reduction gives you the extra torque to turn big tires through heavy terrain. A 15% reduction still adds plenty of grunt while saving more of your top end. The manufacturer's guidelines are meant to keep factory top speed; going with a larger reduction than recommended adds torque and lowers top speed.
Tire Size Guide
| Tire size | Required setup with 4" portals |
|---|---|
| 36" | Stock suspension |
| 39" | 1.5" forward front A-arms |
| 39" | 3" lift kit |
| 41" | 1.5" forward front A-arms and 3" lift kit |
Maximum sizes are measured at full compression and full turn and are the largest that fit without rubbing. With minor trimming or a little rub, larger tires can be used.
Housings and Backing Plates
Cast and billet aluminum housings are both reinforced for gear retention and designed for good oil flow. They're paired with 5/16-inch backing plates made from an advanced steel alloy that's stronger than chromoly. There are no vents on the housings; testing showed vents do more harm than good. GDP's Portal Blood gear oil is formulated specifically for these boxes.
Sealing and Bearings
- Advanced gaskets and O-rings with excellent oil resistance and low deterioration
- Sealed input gear and double-lipped output seal
- Full sealing coverage to prevent oil leaks
- Double-angular contact output bearings resist premature wear
- Roller idler and drive bearings keep gear mesh precise
Frame Stiffener
Portals and monster tires add stress to the frame. Add the optional frame stiffener at checkout to reinforce the chassis, or choose "No" if you already run one.
Is a 4" Portal Right for You?
The 4-inch portal is the most trail-friendly of the GDP heights. It keeps the machine lower than the 6- and 8-inch versions, so it stays more stable in off-camber sections and at speed, while still giving you a big jump in clearance and the gearing to turn 36-inch tires on otherwise stock suspension. It's also the only height here offered with a 15% reduction, which makes it a good choice for riders who want bigger tires without giving up much top speed.
If you plan to build toward 39-41 inch tires, the 4-inch portals work with 1.5-inch forward A-arms and a 3-inch lift to get there, so you can grow the build in stages. If you already know you want 40-plus inch mud tires, compare the 6-inch and 8-inch versions.
Planning Wheels and Tires
Portals change what wheels you can use, so plan the wheel and tire package before you order. Check that your wheels are at least 14 inches, have 5 inches of backspacing or less, aren't dual beadlocks, and have a center bore of at least 3.25 inches; otherwise you'll need a 1-inch spacer. The universal hubs accept the common 4/156, 4/137, 4/115 and 4/110 patterns, so many popular UTV wheels will bolt right on.
Living With Portals
Expect the speedometer to read differently after changing tire size and gearing, and expect a slightly different feel under braking with heavier tires. Check the portal oil level and look for seepage around the seals during regular service, especially after deep water or mud. Re-torque hub and backing plate hardware after the first few rides as everything settles in.
Need Help Choosing?
Between the reduction, housing, idler and frame stiffener options, there are 24 ways to set up this kit. Send us your tire size, wheel specs and how you ride, and we'll help you land on the right combination before you order.
Fitment Notes
- 14" or larger wheel required
- Wheels cannot exceed 5" backspacing
- Not compatible with dual beadlock wheels
- Wheels need a center hole of at least 3.25" (82.55 mm), or a 1" wheel spacer is required
What's in the Box
- (4) Assembled portal hub boxes with 9310 gears, seals, output shaft, gaskets and thrust bearings
- (4) Universal hubs and precision-ground stainless steel slotted rotors with lugs
- (4) Specialized steel alloy backing plates
- (4) Steel caliper mounting plates
- (4) Caliper mounting plate shims (Dual Idler only)
- (4) Caliper adapters
- (4) Brake pad retainer clips (specific models only)
- (2) Steel steering arms
- (2) Aluminum hub adapters
- Extended brake lines
- All required hardware, including a recessed castle nut socket
- Frame stiffener, if selected
Who It's For and What Pairs Well
For Turbo S owners stepping up to 36-41 inch tires for mud, rocks or technical trails. Reach the bigger sizes with RZR Turbo S A-arms and a lift from RZR Turbo S lift kits, and add steering assist from RZR Turbo S steering parts. Compare taller options in RZR Turbo S portal gear lifts.
Fitment
| Year | Make | Model |
|---|---|---|
| 2018-2021 | Polaris | RZR XP Turbo S |
| 2019-2021 | Polaris | RZR XP Turbo S Velocity |
| 2019-2021 | Polaris | RZR XP 4 Turbo S |
Wheel Requirements
- 14” or larger wheel required
- Wheels cannot exceed 5” backspacing
- Not compatible with dual beadlock wheels
- Wheels need to have a center hole of at least 3.25" (82.55mm) or require a 1” wheel spacer
Installation Notes
This is an advanced install. The portal boxes replace the factory hub assemblies at all four corners, with new caliper mounting plates, steering arms and extended brake lines. Bleed the brakes, fill the portal boxes with gear oil and get an alignment when finished. Separate instructions cover single and Dual Idler kits.
- source:
- superatv
- satv_url:
- https://www.superatv.com/polaris-rzr-xp-turbo-s-4-inch-portal-gear-lift-g3
- fitment_raw:
- Polaris RZR XP Turbo S 2018-2021; Polaris RZR XP Turbo S Velocity 2019-2021; Polaris RZR XP 4 Turbo S 2019-2021
- install_pdf:
- https://madmin.superatv.com/amfile/file/download/file/3897/product/14227/
- desc_status:
- rewritten_2026-10-26
- sub_brand:
- GDP
