Holden Commodore Gearbox & Transmission Problems

This could be the result of a worn or poorly adjusted transmission, a worn torque converter or even something simple like a low transmission-fluid level. So that’s job one: Check the level of fluid on the dipstick. If that’s okay, you really need to see a transmission specialist who has probably seen these exact symptoms before. What I can tell you for sure is that the automatic gearboxes fitted to Holdens of this era did have a finite lifespan before they needed either an overhaul or outright replacement.

But make sure your mechanic checks that the cause of the vibration is not a worn universal joint or bent axle or an out-of-balance drive-shaft. Even a sticking brake or a worn engine mount can induce vibrations into a moving or accelerating car, so rule all that stuff out first.

All the V6 Commodores from this era used much the same automatic transmission, a four-speed unit. While most of these units were identical, there were some detail differences across the years, so make sure you get the transmission with the correct number of electrical pins to be compatible with the wiring loom in your car.

It shouldn’t matter whether the replacement transmission came from a car with a floor-shift; it should still hook up to your column shift mechanism with no problems. You might have to swap a few bits and pieces involved in the shifter mechanism to mate it all, but you’ll be able to make it work.

We have seen this problem before in at least one other ZB Commodore, so you’re definitely not on your own. The problem is very possibly caused by a misalignment of the micro-switch that detects the car is, indeed, in Park, and allows it to be powered down. If the computer can’t see the correct signal from this micro-switch or sensor, it assumes the car is not ready to be locked and left.

Given that yours is not the only example of this, perhaps your auto electrician has seen this before and will know what the fix is. Even if they’re not familiar with the problem, a good auto sparky should be able to sort this. If not, a transmission specialist would be your next port of call.

The biggest problem with this model of Commodore was it’s V6 engine and that unit’s propensity to suffer stretched timing chains. Cars without a full service history will be the worst offenders, but even a car with a perfect maintenance track record can still require new timing chains. However, this usually occurs long before 200,000kmk have been clocked up, so it would be very interesting to see if the car you’re looking at has, indeed, had this repair made by a previous owner. Of course, even if the timing chain has been replaced, that’s no guarantee that the problem won’t occur again. There’s also a suspicion that the three-litre version of the Holden V6 was a bit underpowered and needed to be driven hard everywhere; a situation that didn’t help timing-chain wear at all.

Other problems with the VE Commodore generally include some electrical problems that are surfacing with age, particularly camshaft-position sensors, a build-up of carbon on the intake valves which can cause rough running and poor economy, oil leaks and leaks from the cooling system. That said, if you can find a good one with an engine that has had new timing chains, the VE wagon represents a lot of car for not much money these days.
 

It all depends on what engine is fitted to your car, Karen, as Holden used a range of gearboxes in this series of Commodores. If your car is the base-model version (the Omega) it will be fitted with a four-speed automatic (code-named the 4L60E). If your car is an SV6, it will have either a five-speed automatic (5L40E) or a six-speed manual (the Aisin D173/AY6 unit). If your car is a V8 Commodore, it will have either the six-speed automatic (6L80) or a six-speed manual (Tremec T56) fitted.

Of all those transmission options, the five-speed automatic was the odd one out as it was only used from the launch of the VE until the first facelift in 2008 when it was replaced by a six-speed automatic.

Before you do either of those things (replace the engine or the whole car) find out where the coolant is leaking from. You might find that it’s a simple case of a leaking hose or a worn out water pump that is causing the leak. If that’s the case, it could be fixed for a few hundred dollars or perhaps even less. Even if the problem is a rotted welch plug or a blown head gasket, the cost to fix it won’t be anywhere near as high as replacing the engine.

On top of that, you know the history of the engine you have, while a second-hand engine can be a bit of a lucky-dip: You might get a good one, you might not.

This is not an unknown problem with Holden’s Alloytech V6 engine and can often be traced back to a damaged gasket for the thermostat housing which is located at the rear of the engine block. And you’re right, to change this gasket which costs just a few dollars, involves removing the exhaust and transmission. The best advice is to have the thermostat itself changed while all this work is being done, as it will save you going through it all again if the thermostat ever fails (and they have been known to).

But definitely have it checked out as coolant leaks never fix themselves and a small leak today could easily be a big leak tomorrow, leaving you stranded with an overheating engine. Meantime, you might be lucky and discover that the leak is not from the thermostat housing at all. These engines are also prone to coolant leaks from a pair of O-rings at the front of the cylinder heads which can allow coolant to leak through the valley and out the back over the transmission tunnel, making you think the leak is from the rear of the V6. Don’t rule out the water pump as a source of leaks, either. The trade seems to think about 100,000km is the lifespan for an Alloytech V6’s water pump.

I can’t see why not, Peter. The 1996 and 1999 are more or less identical cars so there should be a high degree of interchangeability. While manual versions of the Commodore Ute form this era did, indeed, change gearbox types as the years progressed, the automatic version stuck with the same unit, so the gearbox and all its ancillary bits and pieces should be a straight swap.

And how good is a ute with a bench seat for three and a column-shift? Car makers should revisit this layout as it makes so much sense.

The answer is probably a pretty simple one in terms of what’s causing it. The warning light is to remind you to leave the car with Park engaged. So, the gear selector will have a tiny sensor or micro-switch that detects the selector in the Park position which is then conveyed to the car’s body computer. But if the sensor or switch is faulty or not adjusted correctly, the computer will think the car is not in Park and will light up the warning to alert you. The intermittent nature of the fault is what makes us think this is the case, combined with the fact that a quick flick of the T-bar button is enough to make the warning disappear.

So much for the cause, because the fix might be a bit more complicated. Depending on where the sensors and switches live, you may need to disassemble more of the car than would seem necessary to fix such a seemingly small problem. An auto electrician should be able to make sense of it.

You need to go back to basics here. Check that the battery is connected firmly and that all the connections and low-voltage leads that power and trigger the starter motor are in their correct places and receiving power. Don’t forget to check for earth straps and cables that might have been left off in the reassembly process, too.

If the car is getting power (and the dashboard lights suggest it is) then there’s a problem between the ignition key and the starter motor. Tackle it methodically, checking for power (a test lead or multimeter will be invaluable for this) as you work your way towards the starter motor and you’ll probably find it’s something really simple and basic. Make sure the fuse or relay for the starter motor hasn’t been fried during the gearbox swap, too.