TJ Skid Plates — What the Factory Already Covers, What It Doesn't, and the Tummy Tuck

Start by getting under the Jeep with a flashlight. From the front: the 4.0's oil pan hangs behind the front axle with nothing under it. The steering box sits on the frame rail at the driver's front corner, with its sector shaft pointed down and exposed. Behind those, the transmission is covered by the factory belly pan, which is both the crossmember carrying the transmission mount and the skid — stamped steel, a hair under 1/8 in, and hanging about an inch below the bottom of the frame. It works: a stock TJ can grind that pan over rock for years without hurting the NP231. What it costs is breakover angle, because everything behind the front axle pivots on that low point. Further back, the gas tank sits in a stamped-steel skid bolted to the frame — again, thin but real. On 03–06 Jeeps, the evap canister moved from the engine bay to a bracket near the rear frame and hangs low enough to get torn off. At the very back, the rear differential's stamped cover is the lowest point aft of the axle.

That inventory sets the priority. A bolt-on transfer case skid that mounts under the factory pan — the $100–$150 "heavy-duty TC skid" sold by several brands — adds a half inch of steel below the lowest point on the Jeep. It protects something the factory already protected and gives up clearance to do it. Skip it.

1. Steering box skid ($60–$90, 30 minutes). The sector shaft and the box's lower cover take direct hits on a drop-off; a cracked box is a tow home and $300–$500 for a replacement. Rugged Ridge's bolts to the existing frame holes with no drilling. This is the first skid on any TJ that leaves pavement.

2. Engine/oil pan skid ($250–$320, 1–2 hours). Skid Row Offroad's is the standard and it's year-split (97–02 and 03–06 differ at the front crossmember). It bolts between the frame rails under the pan and front of the transmission. The 4.0 pan is stamped steel and a rock through it empties the engine in under a minute; it also protects the pan from the bump-stop-to-axle contact on a hard front hit. Some designs need two holes drilled in the frame.

3. Rear differential cover ($100–$160, 1 hour plus fluid). Dana 35 or Dana 44, a heavy cast cover (Solid Axle, Riddler, ARB) replaces the stamped one that dents inward into the ring gear. Do it with the next differential fluid change and it's a fluid change plus twenty minutes.

4. Evap canister skid, 03–06 only ($70–$110, 30 minutes). The plastic canister behind the tank is the most commonly destroyed part on a late TJ that wheels; a torn hose sets a check-engine light and an evap code that never clears. Rugged Ridge and Poison Spyder both make a bolt-on cage.

5. Gas tank skid upgrade ($150–$250, 2–3 hours, tank drop required). The factory tray is adequate at stock height. A heavier 3/16 in replacement is worth it on a rig that regularly drags the rear over ledges — dents in the factory skid transfer to the plastic tank and eventually crease it. Most owners do this one only after the factory tray is already deformed.

6. The tummy tuck. Covered below. It replaces the factory belly pan, so it also is your transfer case and transmission skid when you're done.

Rocker protection is armor too, and on a TJ it comes before most of this list; it's a separate guide because it's a separate job — see TJ rock sliders.

A belly-up skid is a flat plate, ¼ in steel or ⅜ in aluminum, that bolts to the frame rails where the factory pan did and carries the transmission mount 1–2 in higher, with a flat bottom that's flush with or above the frame rails. The result is 1.5–2.5 in more clearance at the lowest point and a breakover angle that lets a 33-in-tire TJ go where 35s went before. It is also the job that turns into a project, because raising the transmission and transfer case moves everything attached to them:

• The driveline angle changes. Raising the transfer case tips the rear output down toward the pinion less — good if you have an SYE and CV driveshaft (the belly-up makes the geometry better); bad if you still have the factory slip-yoke driveshaft, which is already marginal on a lifted TJ and will vibrate. Plan on the SYE first. Adjustable rear upper arms or shims to reset pinion angle afterward.
• The engine has to come up with the transmission. A 1 in motor mount lift ($60–$120, Brown Dog or M.O.R.E.) is required with most belly-up skids so the drivetrain rises as one unit; a 1 in body lift ($80–$150) is required with some designs to keep the transfer case out of the tub and the fan out of the shroud. Skids labeled "no body lift required" (UCF's No-BL, Savvy) get their clearance with less rise, and they're the right choice for most owners.
• The exhaust hits the tub. Every tummy tuck needs the exhaust re-routed where it crosses under the transmission — a muffler shop bend, a tuck kit ($80–$150), or a grinder and a flap wheel on the tub seam.
• The shifter linkage binds. The factory transfer case shift linkage doesn't tolerate the case moving up; a cable shifter ($120–$200, Novak or the skid maker's) fixes it and most kits assume you'll add one.
• Year and model split. 97–02 and 03–06 pans differ, and the Rubicon's NV241OR is physically larger than the NP231 — buy the skid for your year and case. It will not swap.

Cost, honestly: skid $350–$600, MML $100, body lift $100 if needed, cable shifter $150, exhaust $100–$200, and if you don't already have one, an SYE and CV driveshaft at $500–$800. Call it $900 with the SYE already done, $1,300–$1,500 without. A weekend of work, most of it under the Jeep on a creeper.

Procedure outline: support the transmission with a jack, unbolt the transmission mount from the factory pan, remove the six pan-to-frame bolts (15 mm and 18 mm heads, two sizes on most years), drop the pan, raise the drivetrain with the MML installed, bolt the new skid to the frame (start every bolt before torquing; the kit's hardware, typically 35–50 ft-lb depending on bolt size), lower the transmission onto the new mount location, then set the exhaust, shifter, and pinion angle. Then check the fan-to-shroud gap, the transfer case-to-tub gap at full articulation, and the front driveshaft at full droop.

1. Lift the Jeep and support the frame on stands; ramps work for the steering box and engine skids.
2. Hold the skid up with a floor jack or a helper — the engine skid is 40–60 lb and awkward.
3. Start every bolt by hand before tightening any; multi-point skids need all the holes lined up at once.
4. Torque to the kit spec with blue thread locker on anything going into a nut plate — vibration backs skid bolts out, and a skid hanging by two bolts is a plow.
5. Check clearance to the exhaust, driveshafts, and steering at ride height and with the axle drooped. A skid that touches the exhaust rattles forever.

• The under-the-pan "TC skid" trap described above. Protection you already have, clearance you lose.
• Aluminum vs. steel belly-up. Aluminum saves 20–30 lb and doesn't rust; it gouges and can crack at the mount tabs under repeated point loads. Steel at ¼ in is the crawler answer; aluminum at ⅜ in is the overland answer.
• Drainage. A flat belly skid without a drain slot holds water and mud against the transmission. Good designs have slots; drill two ¼ in holes at the low points if yours doesn't.
• Steering box skid interference with some aftermarket front bumpers and with hydro-assist ram mounts. Test fit before painting.
• Heat. An engine skid boxes in the oil pan; the 4.0 doesn't care in normal use, but verify the skid isn't touching the exhaust downpipe, which will glow.
• Lifting the Jeep by the skids with a floor jack is fine on a belly-up skid with a jacking pad and a bad idea on a stamped factory pan.

Skid Row, UCF, Savvy, and Poison Spyder sell direct; Rugged Ridge is at every Jeep retailer. Bolt-on TC skids that hang under the factory pan are the one thing on this list to leave on the shelf.

Tools required

• floor jack and jack stands (or a transmission jack for the belly skid)
• socket set with 15mm and 18mm deep sockets
• torque wrench
• drill and step bit (some engine skids)
• angle grinder (belly-up exhaust clearance)
• blue thread locker

Parts

Sources

• The Official Tummy Tuck FAQ Thread (WranglerTJForum)
• UCF transfer case skid for 97-02 TJ, no body lift required
• Skid Row Offroad engine/transmission skid, 03-06 TJ 4.0L
• Transfer case skid plate opinions — factory pan vs. belly-up (WranglerTJForum)

Related

• SYE Kit for the NP231 Transfer Case — Eliminating Driveshaft Vibration
• Rock Sliders and Rocker Guards for the TJ
• TJ Steel Front Bumper — Which Style to Buy and Why
• NP231 Transfer Case — Service and Weak Points
• All Jeep Wrangler TJ guides & tools
• Browse the full DIY database

Written and maintained by an AZ wheeler and driveway wrencher. How we source guides. Always cross-reference your factory service manual — modifications affect vehicle safety and warranty. Work at your own risk.