Every GQ and GU Patrol that rolls into our Burleigh workshop has one of two rear diffs under it, and most owners don't know which. It matters. It decides what ratio you can run, what locker fits, what bearings we order, and whether the whine you're hearing is a $600 fix or a $2,500 one.
Which diff is in your Patrol
The front diff on a GQ (Y60) and GU (Y61) is the H233B. Same unit for twenty-odd years, so parts are cheap and we keep them on the shelf.
The rear is where it splits. Lighter models got the H233B at the back too. The heavier models, the 4.2 TD42 and TD42T, the TB45 and TB48 petrols and most of the ZD30 utes and cab-chassis, got the bigger H260. The H260 has a larger crownwheel and bigger pinion bearings, which is why it shrugs off 35-inch tyres and towing in a way the H233B doesn't.
Quickest way to tell: look at the back of the rear housing. The H260 has a noticeably larger, rounder cover and a cover-plate bolt pattern you won't mistake once you've seen both. If you're not sure, send us a photo of the housing and the compliance plate and we'll tell you.
Ratios, and why you shouldn't mix them
Factory Patrol ratios run 3.9, 4.11, 4.375 and 4.625 depending on engine and gearbox. Rule one: front and rear must match. We see Patrols every month where someone has swapped a rear diff from a wrecker without checking the ratio, and the first sign is the transfer case binding on bitumen in 4WD, then a very expensive noise.
Rule two: if you've gone up in tyre size, your ratio is now wrong for the engine. A TD42 on 35s with the stock 4.11 is lugging; it feels like you've lost a gear. Going to 4.625 or 4.375 brings the revs back to where the engine makes torque, and fuel economy usually improves rather than worsens because the engine isn't being flogged off boost.
We build exchange diff centres for every factory ratio: 3.9, 4.11, 4.375 and 4.625. A centre swap is a one-day job per axle and you keep your housing, axles and brakes.
Open, LSD and lockers
GQ (Y60) and GU (Y61) Patrols have a factory rear limited-slip differential (LSD), with a vacuum-operated rear locker fitted to some models instead. The factory LSD uses clutch packs that wear over time, reducing its ability to transfer drive between the rear wheels. If traction has dropped off, have the LSD checked rather than assuming it is an open diff.
Only some GQ and GU models have the factory vacuum-operated rear locker. If it will not engage, check the vacuum supply, hoses and actuator before condemning the diff. Y62 Patrols have a rear LSD; check the fitted differential and model specification before ordering parts or planning a locker upgrade.
For aftermarket, an air locker in the rear of an H260 is about the best money you can spend on a touring Patrol. Front lockers on the H233B are common too, but the front CVs and swivel hubs become the next weak point once you can put all the torque through one front wheel. We fit ARB and Harrop, and we'll tell you honestly which suits the way you drive.
What fails, in the order we see it
Pinion seal leak. The classic Patrol diff leak. Oil down the back of the housing and onto the handbrake. Often the seal, sometimes a worn pinion flange, and on the H260 the pinion preload has usually gone soft by the time the seal lets go. Replacing just the seal without checking preload is why so many come back.
Pinion bearing whine. A drone that rises with road speed, in and out of throttle. Usually the rear pinion bearing after years of towing or a low oil event. Caught early it's a bearing and reset; left, the crownwheel and pinion are scored and it's a full centre.
Carrier bearing noise. A rumble on cornering, worse one direction than the other. These are the side bearings on the diff carrier. Cheap parts, but the job needs the backlash set properly, which is where backyard rebuilds go wrong.
Chipped teeth. Almost always from a locker being engaged on bitumen or a ratio mismatch. The metal goes through the bearings, so it's a full rebuild, not a gear set.
Breathers. The factory diff breather on a GQ sits low enough to suck water on a creek crossing. Water in the oil kills bearings inside a few thousand kilometres. Extended breathers are a $60 job that saves a diff.
Maintenance that actually matters
Change the diff oil every 40,000 km, or every 20,000 km if you tow or hit the beach. Use a proper GL-5 85W-140 in the H260; it runs hot under load and the thinner oils thin further. If you've got a factory LSD, it needs the friction modifier or the clutches chatter.
After a hard trip, pull the fill plug and look at the oil. Milky means water. Metallic means bearings. Either one means ring us before you drive it far.
When to ring us
If you've got a whine, a leak, or you've gone up in tyre size and the Patrol feels gutless, we can diagnose it in the workshop in Burleigh Heads in under an hour. We rebuild H233B and H260 centres in-house, keep exchange centres on the shelf in every ratio, and fit lockers with the breathers, oil and wiring done properly the first time. Call 07 3924 3317 or book through the site.
