The Common Fault in Holden Colorado RG Rear Diffs (and Why You Need to Catch It Early)

The Holden Colorado RG rear diff has one fault we see more than any other. It comes across our benches in Sydenham week after week, and it follows the same pattern nearly every time. The good news is that you can catch it early. The bad news is that the Colorado hides the noise well, and leaving it too late can easily double the repair bill.

Here is what goes wrong, how to spot it, and what to do about it.

The Holden Colorado RG diff fault: carrier bearings too tight from the factory

The most common failure in a Holden Colorado RG rear diff is the carrier bearings. These are the two bearings that support the diff carrier, which holds the crownwheel, inside the housing.

Every bearing in a diff needs a certain amount of preload. That is the clamping force that holds the bearing snug so nothing moves around under load. Too little preload and things flop about. Too much and the bearing runs hot, struggles to hold an oil film, and wears out well before its time.

In our experience, RG Colorado carrier bearings come over-preloaded from the factory. They are too tight from day one. They run hot and wear fast, and eventually one of them lets go.

Most often, it is the crownwheel side carrier bearing that fails first. Because of the way force is transferred through the diff under drive, that bearing takes the most punishment.

What happens when a carrier bearing lets go

This is where a cheap problem turns into an expensive one.

When a carrier bearing fails, it no longer holds the carrier in the right position. The bearing chews out the carrier where it sits. As a result, the crownwheel and pinion lose their correct mesh, and bearing debris circulates through the oil and the gear teeth. That damages the gearset very quickly.

At that point, the diff cannot be rebuilt with bearings and seals alone. It needs a new gearset AND a new carrier. That is far more expensive than a standard diff rebuild, and it is completely avoidable if you catch the bearings early.

In some extreme cases, the damage goes further still. The failed bearing can damage the crownwheel side of the diff carrier itself, and then that needs replacing too.

Caught early, it is a routine job: strip the diff, fit quality bearings, set the preload correctly, and reuse your good gearset and carrier. Caught late, you are paying for the hard parts as well.

Either way, we keep rebuilt exchange diffs for the RG Colorado on the shelf. The difference is the core. If you catch it early, your old diff comes back to us with a good gearset and carrier, and you avoid any core charges. Leave it too late and the core is damaged, so those charges apply.

Warning signs of a failing Holden Colorado RG diff

These are the most common ways people pick up a fault in a diff:

• A whine or hum that changes with road speed. It rises and falls with how fast you are travelling, not with engine revs. If the pitch follows the speedo, suspect the diff. We cover this in more detail in our guide to what causes diff whine.
• A droning noise under load. It often gets louder when towing, carrying weight, or accelerating up a hill, and may ease off when you coast.
• Play in the diff. A clunk when you take up drive or shift between forward and reverse, or movement a workshop can feel when checking the diff on a hoist.

There is a catch with the Colorado, though. These utes do not transmit noise into the cab as well as other vehicles. Normally that is a positive, but not when there is a failing diff. By the time you can hear noise from a Holden Colorado RG rear diff, it is usually extremely bad. Any one of these signs means the diff needs an inspection now.

The best early warning: routine diff oil changes

The best way to catch a failing diff early in a Holden Colorado is to keep up to date with routine oil changes. The condition of the oil that comes out tells you what is happening inside. Metal fragments or contamination in the old oil show up long before the noise does, so you can repair the diff before it costs you more.

If you are a workshop servicing an RG Colorado, take a good look at the diff oil as it drains. Anything that glitters is worth a phone call.

Suspect it? Here is what to do

Stop driving it hard. No towing, no heavy loads, no long highway runs if you can avoid them. Every kilometre on a failing bearing brings it closer to letting go, and heat and load speed that up.

Get it inspected. A diff specialist can confirm carrier bearing wear quickly. If you are a workshop and a customer’s RG Colorado comes in with a speed-related whine from the rear, give us a call before it goes back out the door.

Do not wait for it to get louder. In a Colorado, noise you can hear from the cab means the damage to the carrier and gearset has usually started. Every day you wait adds to the bill.

We keep rebuilt Holden Colorado RG diffs on the shelf

Here in Christchurch, we rebuild Holden Colorado RG rear diffs, with the bearing preload set correctly so the factory fault does not come back. We also keep rebuilt exchange units ready to swap, so your ute is off the road for hours, not weeks. For workshops, that means no hoist tied up waiting on a repair.

We supply exchange diffs NZ-wide, so it does not matter where in the country you are. Not sure which way to go? Read our guide to repair or exchange.

Think your Colorado’s diff is making noise? Call George on 03 381 0320.