Rear differential rebuild: how a Patrol H233B or H260 is done properly

A rear diff rebuild is one of those jobs where the parts cost $400 and the skill costs the rest. The bearings are the same whoever fits them. Whether the diff is quiet in 100,000 km comes down to three measurements most people skip. This is how we do a Patrol rear diff in Burleigh Heads, and why we don't do it cheap.

The symptoms, and what each one means

A whine that rises with speed and changes on and off throttle is the pinion. On throttle noise is the drive side of the gear; off throttle is the coast side. If it's both, the pinion bearings are gone and the gear faces are probably marked.

A rumble or growl on corners is the carrier (side) bearings; it loads up on the outside wheel.

A clunk on take-off or when you lift off is backlash. Either the crownwheel bolts have stretched, the carrier bearings have collapsed and let the crownwheel move, or on a factory LSD the clutch pack has worn.

Oil on the handbrake is the pinion seal, and on an H260 the preload is nearly always gone soft by the time it leaks.

Milky oil at the fill plug is water from a crossing. Don't drive it far.

What a rebuild actually involves

We pull the centre from the housing, strip it on the bench and measure everything before ordering parts.

Pinion depth. The pinion has to sit at exactly the right height relative to the crownwheel, set with a shim behind the inner pinion bearing. Get it a few thou out and the gear teeth mesh on the wrong part of the face; it'll be quiet for a month and then whine forever. On the Patrol diffs this is set with a depth gauge and confirmed with a marking compound pattern. There's no shortcut.

Pinion preload. The two pinion bearings are squeezed together to a set rolling torque. The H233B and H260 use a crush sleeve from the factory. We replace the crush sleeve on every rebuild and set preload with a torque wrench on the pinion nut and an inch-pound gauge on the rotation. Reusing a crush sleeve, which some workshops do, is why the seal leaks again in a year.

Carrier bearing preload and backlash. The carrier sits between two side bearings with shims (or adjuster nuts on some units) that set both how tight the carrier is and how much backlash there is between crownwheel and pinion. Patrol spec is roughly 0.13 to 0.18 mm. Too little and it heats and whines; too much and it clunks and the teeth hammer.

Pattern check. Marking compound on the crownwheel, turn it through, read the contact patch on both drive and coast sides. If the pattern isn't centred we go back to pinion depth. This step is the difference between a diff that lasts and one that doesn't.

Crownwheel bolts, seals and the rest. New crownwheel bolts with thread locker, new pinion seal and flange nut, new axle seals if there's any weep, cover gasket, and a fresh fill of GL-5 85W-140 (with friction modifier if it's a factory LSD).

Rebuild in place or exchange centre

If your diff is a plain open H233B or H260 with a damaged gear set, an exchange centre is quicker and often cheaper: we have rebuilt centres ready in 3.9, 4.11, 4.375 and 4.625, so the Patrol is off the road for a day rather than a week. Your old centre comes back to us as the core.

If you've got a factory LSD you want to keep, a locker already fitted, or a ratio we don't have on the shelf that week, we rebuild your centre.

If you're changing ratio for bigger tyres, you need both ends done at once. We do front and rear as a pair; a Patrol with mismatched ratios will destroy its transfer case in 4WD.

The honest cost picture

Parts for a bearing-and-seal rebuild on an H260 are a few hundred dollars. Labour is most of a day, because the setting-up is the job. A full centre with a new crownwheel and pinion is considerably more, and at that point an exchange centre is usually the better value. We'll quote both after we've had the cover off. What we won't do is a seal-and-bearings job without setting preload and backlash, because that's the one that comes back.

If your Patrol has started to whine, or you've got oil on the back of the housing, ring 07 3924 3317 or book online. We can usually have a look the same week.