Yukon Gear Replacement 27 Spline Standard Open Spider Gear Kit For Jeep JK Dana 30 Front

A click every wheel turn in a tight parking lot, a clunk when you hit the throttle mid-turn in 4WD, or chunks of gear tooth on the front diff magnet all point at the spider gears in a Jeep Wrangler JK front axle. The Yukon YPKD30-S-27-JK is a complete replacement spider gear kit for the open differential in the 2007-2018 JK Dana 30 front axle, the non-Rubicon front end, with 27-spline side gears to match the stock front shafts.

What the spider gears do in a JK Dana 30

Inside the front carrier, two side gears are splined to the inner axle shafts and two pinion gears ride on a cross shaft between them. Driving straight in 4WD the whole pack turns as one piece. In a turn, or when one front tire lifts or slips, the pinion gears spin on the cross shaft so the two wheels can turn at different speeds. On an open front diff that is also how torque escapes to the tire with the least grip: the spinning side runs the spiders flat out, and when that tire bites again the shock load lands on these small gears. That is why oversized tires, wheel hop on climbs and bouncing a lifted tire in the rocks are what usually break JK front spiders. The JK front is a high-pinion, reverse-rotation Dana 30, but the spider gears only care about the carrier and spline count.

Symptoms of failing front spider gears

• Clicking or ratcheting from the front in slow, tight turns with 4WD engaged
• A bang or clunk from the front when power goes down mid-turn
• Noise that shows up only in turns while straight-line driving is quiet
• Steel slivers or a broken tooth on the cover magnet, not just fine grey paste
• Slop you can feel rocking one raised front tire while the other is held

How to confirm before you buy

Drain the front diff and look at the oil and magnet first. Then pull the cover, rotate the carrier slowly and look at every spider and side gear tooth, and check the cross shaft for a polished step where the pinion gears ride. Make sure the cross shaft lock bolt is present and tight. Our spider gear failure guide covers the inspection. If the noise follows road speed in a straight line instead of only in turns, suspect the ring and pinion or bearings; a Yukon JK Dana 30 master overhaul kit addresses that.

Fitment

This kit fits the Dana 30 front axle under 2007-2018 Jeep Wrangler JK models with the standard open front differential, which means every JK that is not a Rubicon. It needs 27-spline inner axle shafts, which is what the stock JK front uses. It does not fit the Rubicon, whose front axle is a Dana 44 with an electric locker, and it does not fit the 2018-and-later JL, which uses a different front axle. If your JK has an aftermarket locker, limited slip or 30-spline shafts, this open-carrier kit is not for you. When in doubt, read the axle tag, count the shaft splines, or send us your year and VIN before ordering. Shop more JK and Wrangler parts in our JK Dana 30 bearing kit listing as well.

Install notes

• The kit includes two side gears, two pinion gears, a new cross pin shaft and lock bolt, and the spider gear thrust washers, with conical side gear thrust washers, so nothing old goes back in.
• With the front inner shafts pulled back to clear the side gears, the lock bolt and cross shaft come out and the pinion gears roll out through the carrier windows. Many shops pull the carrier anyway so they can check the carrier bearings while they are in there.
• Coat all thrust washers and gears with gear oil before assembly, and use thread locker on the new cross pin bolt.
• Pull and reinstall the inner shafts carefully so the splines do not cut the inner axle seals. The Dana 30, 44 and 60 inner axle seal installer lets you seat new seals square if they leak.
• If the carrier case itself is cracked or the cross shaft bore is egg-shaped, replace it with the Yukon JK Dana 30 open carrier case, 3.73 and up.
• Refill with 75W-90 gear oil. An open front diff does not need friction modifier.

Plan on most of a day for the job; the inner shafts on a JK can fight you coming out of the knuckles.

Does this fit a JK Rubicon?

No. The Rubicon front axle is a Dana 44 with a factory electric locker. This kit is for the non-Rubicon JK Dana 30 with the standard open front differential.

What comes in the kit?

Two side gears, two pinion (spider) gears, a cross pin shaft and bolt, and the spider gear thrust washers, including conical side gear thrust washers.

Do I have to remove the ring gear or reset the gear pattern?

Usually not. Spider gears live inside the carrier, so replacing them does not change the ring and pinion setup as long as the carrier goes back on its original bearings and shims. Check backlash if the carrier came out.

Will it fit a 2018-and-later Wrangler JL?

No. It is listed for the 2007-2018 JK only. The JL uses a different front axle and needs its own parts.

What oil goes in afterward?

Use 75W-90 gear oil. The stock JK front diff is open, so friction modifier is not needed.