BIG BORE XD® Cylinder Assist® Steering Gear – Jeep Wrangler JK/JKU (2007–2018)
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BIG BORE XD® Cylinder Assist® Steering Gear – Jeep Wrangler JK/JKU (2007–2018)

$1,450.00 In Stock Pre-Order Sold out
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  • Description
  • Shipping and Refund
  • Reviews

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 45mm 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.

  • 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

Head's 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

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

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)

What's Included

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

🧾 Rock Rig Supply Return Policy

At Rock Rig Supply, we get it — sometimes a part just doesn’t fit the build, or a project takes a left turn halfway up the hill. We’ve been there. That’s why our return policy keeps things simple, fair, and flexible (because real-world wrenching isn’t always perfect).

🕒 1. Return Window

  • Returns are accepted within 30 days of delivery.

  • Items must be unused, uninstalled, and in original condition with all packaging.

  • Every return gets inspected before we process it — we don’t cut corners, and we don’t want you to either.

🔧 2. Custom & Built-to-Order Parts

  • Custom, one-off, or built-to-order parts carry a 50% restocking fee.

  • They’ve been made just for you, so we can only take them back if they’re unused and still in sellable shape.

💰 3. Refunds & Store Credit

  • You can choose between a refund or store credit after your return is approved.

  • Some items may have an additional restocking fee depending on condition.

  • Refunds typically appear 7–10 business days after approval, depending on your bank.

🚚 4. Return Shipping

  • If we messed up (wrong item, damaged, or defective), we’ll cover return shipping and send you a replacement on our dime.

  • If it’s a “changed my mind” or “wrong fit” situation, you’ll cover return shipping.

  • Not sure which way it goes? Shoot us an email at rockrigsupply@gmail.com and we’ll help you sort it out.

⚙️ 5. Used or Installed Products

We know how it goes — sometimes you bolt something up and realize it’s not gonna work.
If the part’s been used or installed, email us first at rockrigsupply@gmail.com.
Returns for used parts are handled case-by-case at our discretion because we understand that not every project goes as planned.

🧰 6. Garage Sale Items

Our Garage Sale section is full of awesome deals — open-box, blemished, and used parts that still have plenty of life left.

  • All Garage Sale items are sold “as-is.”

  • No returns, refunds, or warranties on these.

  • We do our best to describe the condition, but little quirks or wear come with the territory.
    You’re scoring a deal, and we’re clearing the shop — win-win.

🔄 7. Exchanges & Buy-Backs

  • Unused, uninstalled items qualify for free exchanges or store credit.

  • If a part’s been installed or opened, we may offer a buy-back depending on its condition and resale potential.

🚫 8. Non-Returnable Items

  • Gift cards, Garage Sale items, and consumables (fluids, sealants, etc.) are non-returnable.

  • Items missing packaging or showing heavy use may be denied or refunded at a reduced rate.

📬 9. How to Start a Return

  1. Email rockrigsupply@gmail.com with:

    • Your order number

    • Photos (if damaged or defective)

    • A short note about what’s going on

  2. We’ll reply with return instructions or a prepaid label (if applicable).

  3. Once inspected, we’ll issue your refund, store credit, or exchange.

💪 10. The Rock Rig Guarantee

We actually run the parts we sell — they’ve been hammered, flexed, and tested on real trails. If something doesn’t hold up or doesn’t meet your expectations, reach out. We’ll make it right, because that’s how we’d want to be treated.

Contact: rockrigsupply@gmail.com