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  • Black PSC steering gear assembly displayed with pitman arm and mounting hardware on a white background.
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BIG BORE XD® Steering Gear - Jeep Wrangler JK / JKU (2007-2018)

BIG BORE XD® Steering Gear - Jeep Wrangler JK / JKU (2007-2018)

$1,450.00
$1,450.00
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Part Number: SG688R

Do you want Cylinder Assist® Now for Future Plan?

The stock JK steering box? It’s fine for stock tires and errands. But throw on 37s, a locker, and a weekend in Moab, and that thing’s begging for mercy. The BIG BORE XD is the fix—built with a beefy 45 mm sector shaft and a reinforced case so it won’t twist, crack, or cry when you crank it hard. Pair it with a PSC High-Flow Pump Kit and you’ll feel the difference the first time you turn the wheel—smooth, strong, and no more arm wrestling at the trailhead.

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PSC TRAIL SCORE

3/5

Weekend Warrior

Balanced for street and moderate trails—think mild rock and mud.

About:About:

Why you’ll love it

  • 45mm sector shaft – nearly 30% bigger than stock for serious strength
  • 16:1 ratio with 80mm piston – more torque, better road feel
  • Includes PSC proprietary Pitman arm – no guessing, no mismatched splines
  • Bolt-on upgrade – fits JK/JKU with factory mounts
  • Handles 35s without assist – and Cylinder Assist® makes it unstoppable

Tech InfoTech Info

Heads‑up for installers

  • Weight warning: This gear tips the scale at ~57 lbs. Use a jack or a buddy.
  • Track bar brace caution: If you’re running a Synergy MFG
  • Front Track Bar Brace (or similar), you must add PSC HWK-688-PP Bolt Kit (110mm). Using factory or PSC 100mm bolts can crack the case.
  • Pump matters: This gear needs a pump that can deliver ~1650 PSI and 50% more flow than stock. PSC pump kits are tuned for it.
  • Bleed it right: Front tires off the ground, engine off, cycle lock-to-lock, then recheck fluid.
  • Pitman arm note: Supplied arm has no extra drop. Some setups may need a drag link flip kit for proper geometry.
  • Recommended Tools:

    46mm Pitman Arm Nut Socket
    Pitman Arm Puller
    Tie Rod End Puller
    Axle Caster Gauge
    Pneumatic Anaerobic Thread Sealant

Fitment

  • 2007–2018 Jeep Wrangler JK & JKU
  • Direct bolt-on for factory steering gear location
  • Works with most aftermarket track bar braces (see bolt note above)

Use it with

  • PK38JP1 – High-Flow Pump Kit for 3.8L JK
  • PK36JP1 – High-Flow Pump Kit for 3.6L JK
  • PSC Cooler and Inline Filter (always a good idea on big steering systems)
  • PSC Cylinder Assist® Kit for JK (if you’re stepping up to 40s or hardcore trails)

Ideal for

  • JKs on 35s–40s
  • Rigs with front lockers or heavy bumpers/winch setups
  • Daily drivers that double as weekend trail rigs
  • Builders planning for Cylinder Assist® down the road

Specs

  • Sector Shaft: 45mm (stock is 35mm)
  • Gear Ratio: 16:1
  • Piston Size: 80mm
  • Ports: Metric O-ring (PSC includes adapters in kits if needed)
  • Case: Reinforced mounting pad and housing
  • Weight: ~57 lbs
  • Includes: PSC proprietary Pitman arm

What’s included

  • BIG BORE XD® Steering Gear (SG688)
  • PSC proprietary Pitman arm

Overall rating: 5.0 / 5 from 1 reviews.

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Reviews

⭐⭐⭐⭐⭐ PSC Big Bore Review (For the “You Don’t Need

"Installed a PSC Big Bore on my JK with one-tons and 40s. According to the internet, I should’ve just aired my tires down, adjusted my toe, rebuilt my track bar, changed my caster, rotated the tires, replaced every steering component twice, sacrificed a goat under a full moon, and accepted that “it’s a Jeep thing. ” Instead… I installed the PSC. Now it steers like a normal vehicle. Imagine that. No more sawing the wheel around like I’m trying to land a shrimp boat in Galveston. The front tires actually listen instead of holding a committee meeting every time I turn. If you’re still running 40s on a stock steering box because “mine’s been fine for years,” congratulations. Some people also say 35s are the biggest tire you need. The PSC Big Bore doesn’t magically fix bad geometry, bent links, or junk parts. But if your suspension is dialed in, this thing is worth every penny. Would recommend."

— C K. (5/5)

Q&A

California Prop 65 Warning

California Prop 65 Warning

This product can expose you to chemicals including lead and di (2-ethylhexyl) phthalate, which are known to the State of California to cause cancer, birth defects or other reproductive harm.

For more information, go to www.P65Warnings.ca.gov