QOTW #96 – 6 speed V8/ V12 gearbox whine, is it normal?!

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This week, it’s the six-speed Graziano gearbox fitted into V8 and V12. You may remember from previous videos; we’ve talked about the crunch into second gear when cold. With a stiff bulking on the synchromesh, that first time going into second when the gearbox is cold is fairly normal. Some owners double declutch drive around that problem, some go from first into third. And then after a few shifts on the move going into second is then fine no problem at all. We said in that video that the gearbox was often described as being agricultural. You know it makes a few harsh noises. It’s a bit clunky. It’s not the ultimate precision gearbox but it’s durable.

Arising from that video, some people also commented that they’ve got a bit of gearbox whine. Now whether that was gear whine or diff whine. Who knows until we can assess the car? Whining in fifth and six and diff whine is another common feature of those gearboxes. The factory must have lost count how many they’ve changed during the original three-year maker warranty period. Because obviously during that period of time if you’re upset if it’s niggling you if the noise is annoying it doesn’t have to mechanically fail. Then you can say, look this is outside of specification and I’d like a new gearbox.

Please if the new owner of the car back in the day wasn’t that critical and it never got changed and now maybe owner two owner three, you are very critical and you’re picking up quite an annoying intrusive gearbox whine. Unfortunately, the approved used timeless warranty is unlikely to take care of you. Because that is just going to fix a mechanical breakdown and not a niggle of a certain problem. Perhaps if you complained enough, you’d get a goodwill gesture out of the factory and they would replace the gearbox, but it wouldn’t be the approved timeless. Third-party insurance policy that pays for that, because they only pay for outright breakdowns.

The Graziano 6-speed gearbox has been plagued since production of DB9 manual with diff whining. No rhyme or reason to it doesn’t appear to be linked to service you know if the diff oil was stretched out a bit too far anything like that. It’s just individual components that cause the problem. So, if we just remind ourselves of the gearbox layout, here’s a picture of the gearbox in its entirety. At the bottom of the picture, we’ve got the differential housing and towards the top of the picture is the actual gearbox. This is the top of the gearbox and this shaft locates into the talk tube. This is a close-up of the differential unit, and inside the differential unit you’ve got the crown wheel and pinion.

Surface isn’t perfect, maybe there’s some imperfections causing a whine. Maybe the setup of the preload isn’t quite right and meshing is incorrect out of tolerance. So, incorrect build can cause the whine. In both cases, a diff whine like that is going to run forever in reality and rather than there being a problem that is going to cause a failure down the road. Sometimes it’s just a very intrusive annoying noise to put up with in the cabin. Similarly, if it was a gear whine, this is gonna be a meshing problem between gears. Setup isn’t quite right and the type of bearing used can create a noise.

You know we’re not talking about this gearbox using the very best metal bearings. The plastic case bearings in these gearboxes are going to run louder than more precision bearings. So, we’re going to listen to a video that I took in a car where the customer brought it to me to assess the diff whine. And he also brought his sheet from the dealer, where he raised the diff whine with the dealer. And here the dealer writes, “Customer has mentioned whining present in sixth gear. Whine can be heard in fourth, fifth and sixth. These gearboxes can be louder than other conventional manual gearbox. Due to smaller tolerances within the construction of gearbox, it’s recommended to oil change frequently. Because oil can deteriorate over time.”

I don’t know if it’s a case of believing their own VS or they just cannot state what the truth is. You know this gearbox has not got tighter manufacturing tolerances, because it’s a performance or luxury car gearbox. Actually, the reason that any gear set makes a noise is because of the opposite of that. The tolerances are bigger than what they’re supposed to be. In this particular case with the diff Whine is because the surface finish isn’t perfect and because the preload setup on the crown wheel and pinion isn’t perfect. One particular customer that was very critical of gearbox noise here, we took the gearbox apart, we shot pinned and super polished finished every gear surface.

When that gearbox was rebuilt and put in the car, it drove the car down the road and it’s as if someone had chopped the back end of the car. The noise that you can normally hear in these cars in the rear environment had just completely gone. Because the gearbox was running so smooth, up specked bearing carriers and metal finishes that have been shopping and super polished finish. That is the way you build a gearbox with such precision that you get no noise from. It’s quite funny how this dealer thinks it’s the opposite of that in that the precision build causes noise. So, this is sixth gear at about 65 mile an hour. We’re just very lightly resting our foot on the throttle and just going for a gradual acceleration. And you can hear this noise quite intrusively in the cabin.

If you apply more throttle and put more torque and more load through the drivetrain, the noise actually disappears. Just happens at the onset of torque being delivered. So, you know this is absolutely no problem whatsoever. It’s not going to result in a failure down the road. I doubt it’s ever going to get any worse than this. It’s just extremely annoying to live with this whine inside the cabin at what is typically a regular cruise condition. So, another one of those things to check for a point of purchase, just get it on cruise, lightly go on and off the throttle. Just check that you haven’t got any diff whine, at the same time you know a little bit turn to the left a little bit turn to the right rule out any wheel bearing noise. There are two checks to do on the go pretty much at the same time.

If you didn’t spot that noise at a point of purchase because you’re too wrapped up in the novelty of being in the Aston and it’s something you noticed now that you’re getting used to the car. Oh, it’s extremely annoying. Probably the original owner should have been more critical and that problem would have got fixed under warranty. Unfortunately, the extended warranty isn’t going to take care of this, because it’s not breakdown, it’s just something you’d have to live with unfortunately. But at least be reassured that it’s unlikely to develop into any more serious problems.

Really like to hear your comments on the six-speed gearbox fitted in the V8 and V12. Hope you like that question of the week.

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