Dana Trac-Lok
Limited Slip Chatter Fix

A Trac-Lok that chatters in a parking lot is almost never broken. Nine times out of ten it is starved of friction modifier or running the wrong gear oil, and a $60 drain-and-fill makes it quiet again. The other times the clutch packs are glazed or worn flat, and no bottle of additive is going to save them. The trick is doing the cheap fix properly before you spend money on the expensive one.

Which Axles Have a Trac-Lok

• Jeep Dana 35 rear. Optional on XJ Cherokee, TJ Wrangler, ZJ Grand Cherokee and KJ Liberty-era vehicles. Small clutch packs and 27-spline C-clip axles. The weakest of the bunch.
• Jeep Dana 44 rear. TJ, JK non-Rubicon, WJ Grand Cherokee and some XJ and ZJ. Rubicons got lockers instead. TJ-era is 30-spline, JK is 32-spline.
• Chrysler 8.25. Dakota, Durango, Ram 1500 and later XJ and KJ rears with a 10-bolt cover. Same clutch-type design, 27 or 29 splines depending on year.
• Chrysler 9.25. Ram 1500 and 2500 rears and 2500/3500 front axles. Uses the same clutch kit as the Dana 44.

Check the axle tag on a cover bolt or the build sheet; many limited slip axles also carry an additive warning tag near the fill plug.

What Chatter and Clunk Actually Are

Inside a Trac-Lok, a clutch pack sits behind each side gear. A preload spring, an S-shaped spring between two plates, pushes both packs outward so the side gears are always lightly locked to the case. In a turn the outside wheel has to overrun the inside one, so the clutches must slip.

When the plates slip smoothly, you feel nothing. When the oil lacks friction modifier, the plates grab, release, grab again. That stick-slip is the shudder, chatter or ratchet you feel through the floor at walking speed in a tight turn, usually worst when the oil is cold. A single heavy clunk or a bang mid-turn is the same thing, the packs holding too long and then letting go all at once.

Rule out the stuff that sounds similar. U-joints and a loose pinion yoke clunk on throttle changes, not just in turns. A worn cross shaft clicks on direction changes, so look for a wear step on it when the cover is off.

Step 1: Drain and Fill With Friction Modifier

Do this first, every time. Pull the cover rather than just the drain plug, because most of these axles have no drain plug and a suction pump leaves old oil in the bottom of the housing. Clean the magnet, scrape the gasket faces and reseal with RTV.

Fill with GL-5 gear oil to the bottom of the fill hole, then add 4 oz of limited-slip friction modifier. A quart-bottle fluid transfer pump ($19.99) makes the job clean, because the fill holes on all four axles are awkward to reach. Gear oil and additive are in our fluids section.

Capacities vary by year and tube length, so always fill to the hole rather than to a number. Some synthetic gear oils are sold as limited-slip ready with modifier already blended in. With those, add 2 oz, drive it, and add the other 2 only if it still chatters. Overdosing has a cost: too much modifier makes the clutches slip so easily the axle behaves like an open diff.

Step 2: Drive the Figure-Eights

Fresh modifier has to get between the plates. In an empty lot, drive 10 to 20 slow, full-lock figure-eights, in 2WD if it is a 4x4. You will often feel the chatter fade halfway through. Glazed but healthy plates can take a few hundred miles to fully settle.

If the chatter is gone and the axle still pulls both wheels on a wet or gravel launch, you are done. Change that oil every 30,000 miles or so, sooner if you tow or wade water. Our differential fluid change interval guide has the schedule.

Step 3: Test the Clutches

If it still chatters, or it never seems to lock anything, check breakaway torque. In 2WD, transmission in neutral, parking brake off, raise one rear wheel and leave the other on the ground. Put a torque wrench on a lug nut and turn the raised wheel. A healthy Trac-Lok takes real effort and turns smoothly. If it turns with roughly under 35 ft-lb, or breaks loose in jerky steps, the packs are flat or glazed.

Step 4: Rebuild the Clutch Packs

On a Dana 44 or Chrysler 9.25, a clutch rebuild is the value move. The Yukon Trac-Lok clutch kit for Dana 44 and 9.25 ($146.82) replaces the friction discs, steels and shims. You pull the axles, take out the cross shaft, then rotate the pinion mates out of the case against the preload spring with a step plate and forcing screw. A flat-blade screwdriver and a prayer is how people launch S-springs across the shop.

Budget about 3 to 5 hours of shop labor with the carrier staying in the housing. Soak the new frictions in oil and modifier first. Replace the cross shaft if it has a visible wear step, and replace the side gears or pinion mates if the teeth are chipped. If the carrier bearings are rough while you are in there, see our Dana 44 rebuild cost guide.

The Dana 35 and Chrysler 8.25 are a different call. Their packs are smaller and the C-clip axles and housings are weaker, so a full replacement carrier often makes more sense than chasing a rebuild. We carry the Yukon Dura Grip posi for Dana 35, 27-spline, 3.54 and up ($807.50) and the Yukon Dura Grip for 1997-up Chrysler 8.25, 29-spline ($804.42). Pulling the carrier means setting backlash and carrier preload again, so do the bearings at the same time with a Dana 35 master bearing kit ($212.99).

When to Quit the Clutches Entirely

If you have rebuilt it once, still fight chatter every oil change, or you run big tires off-road, stop paying for clutches. A gear-type Truetrac has no clutch packs, never needs friction modifier, and never chatters. It is smooth on the street and lasts the life of the axle. Its one weakness: with a wheel completely in the air it acts open, so tap the brakes lightly to load it. For a JK Dana 44 rear, the Eaton Detroit Truetrac for Dana 44, 32-spline ($1,044.99) drops in where the Trac-Lok was.

A full locker is the answer for rock crawling but it is loud and pushy in turns on the street,. Our open vs limited slip vs locker guide covers which fits how you drive.

What It Costs

Carrier swaps assume new carrier bearings and a reset of backlash with a dial indicator. If the noise turns out to come from the transfer case or transmission instead, CoreTransmissionParts.com carries the rebuild parts.

FAQ

How much friction modifier does a Trac-Lok need?

The factory call is 4 oz of limited-slip friction modifier added to the gear oil on a drain-and-fill. If the gear oil is already labeled limited-slip ready, start with 2 oz and add the rest only if it still chatters after figure-eights. Too much modifier lets the clutches slip and the axle acts close to open.

Why does my Trac-Lok still chatter after I added friction modifier?

Either the old oil was never fully drained, the modifier was not worked into the clutch packs, or the clutches are glazed. Drive 10 to 20 slow, tight figure-eights in each direction to soak the plates. If the chatter is still there after a few hundred miles on fresh oil and modifier, the clutch packs are glazed or worn and need replacing.

How do I test if my Trac-Lok clutches are worn out?

With the vehicle in 2WD and the transmission in neutral, raise one rear wheel and turn it with a torque wrench on a lug nut while the other wheel stays on the ground. If it turns with very little effort, roughly under 35 ft-lb, the clutch packs are flat. A healthy unit takes noticeably more torque to break loose and turns smoothly.

Should I rebuild my Trac-Lok or replace it with a Truetrac?

On a Dana 44 or Chrysler 9.25 a clutch kit is cheap and brings it back for another 60,000 to 100,000 miles if the cross shaft and side gears are clean. On a Dana 35 or Chrysler 8.25 that needs a full carrier anyway, or if you are tired of friction modifier and chatter, a gear-type Truetrac or a new clutch-type carrier is the better use of the labor.