348 - How much gearbox noise

I would personally be concerned, my 348 has no discernible noise in any gear. If it is the same for every gear I'd suspect rear end though, or I suppose it could be a bearing, or even a CV joint. I would check the latter first, are the CV joint boots intact? Look for grease being ejected surround the joints or obvious torn boots. It might also be wheel bearings.

Is the noise still present coasting in neutral? If so you can be sure it's not a problem with a specific gear obviously.

 

You should not have any noise coming from the gearbox.

The 348 gearbox is know to have a few issues though.

1) the bearing, on the transmission oil pump side of the the layshaft, is know to go bad, and the ring nut may not have been secured properly.

2) the ring nut for the drop gear (accessed from the clutch bell housing) has been know not to have been secured properly. Meaning it did not get staked properly to help prevent it from backing off.

I would first drain the gearbox oil to check for bits of metal in the oil. Also run a search of the archives, as this topic has been discussed in the past.

 

It's not you, the search feature on this site blows.

Can you get us a better and closer pic of that ring nut?

 

Make sure there is no lateral play in the layshaft, or the main shaft for that matter. When my gearbox bit the dust what happened was, the bearing cage failed. That allowed the shaft to move back and forth, further wearing out the cage until it broke. Once it broke it sent bits of broken cage through the gears and destroyed my ring and pinion gear, as well and doing damage to one of the gear (4th iirc), and wearing the the sychros out on the gear also. This thread has some of the play by play from fatbillybob and I digging into mine. http://www.ferrarichat.com/forum/technical-q-sponsored-algar-ferrari/77427-tranny-done-blowd-up.html

Using a mechanics stethoscope, see if you can pin point where the noise is coming from. The oil pump bearing is on the left side of the gearbox, the side that the speedometer sensor is mounted on. I would start listening to that area of the tranny.

You know what, where is fatboy? Someone get fatbillybob to chime in on this.

 

have you thought about the differential?
backlash might be off

 

There can still be a bad bearing in there somewhere. I have overhauled a number of gearboxes and it is not always obvious. Problem is that when not under load it will be difficult to find.
Was the noise present in all gears?
Perhaps you already found it, I think you will find this thread useful: http://www.ferrarichat.com/forum/348-355-sponsored-bradan/234915-348-ratio.html

 

WDA, there are always clues in when the sound appears. For instance, in most conventional gearboxes (not the 348) there is one gear that is direct-drive, meaning it goes in-out the box and does not load up the layshaft. If a box is noisy in all gears but quiet in that gear, it is very likely that there is a layshaft bearing problem.
If the sound is there mainly under acceleration, then look at how the gears are toothed, they are always slanted which loads up one bearing more than the other, providing more clues as to where the noise emanates.
I do agree with others here, a good gearbox is a quiet gearbox. If there is more noise than you think should be there, grinding, growling or whining, you have an issue; and it never goes away by itself. But do "write down" in your memory or otherwise when you have the most audible noises - what gear, what load, what rpm. Making videos rowing through the gears can do that trick too.
One thing, do check out the engine/transmission rubbers. Having a failed rubber insulator can transmit a lot of noise into the cabin leading you to think there is an issue.

 

Well it does look as if it has bearings with brass cages. These are very good and durable but can be noisier than bearings with pressed steel cages, let alone plastic.
If you study the drawings of the box, understand how the forces work and combine that with the noises you are hearing you can often make a good assumption as to what is going on. Layshaft bearing problems are the most common in gearboxes because those usually get the most forces on them.

I am not sure Ferrari will be able to help apart from sell you a new gearbox, some mechanics of such garages have never seen the inside of one. I'd ask them whether they also have experience fixing them - if not what would the added value be?

 

They really are quite simple. Very ingenuous, but simple in principle. Depending on the access you have now with the cover off, you can try to evaluate the axial play of the shafts, best done with a measuring clock to the side of one of the (integral or fixed) gears of the shaft. You can rock the shafts left and right with a screwdriver or similar. That action should give you an idea of play - there should be none or only very little. Unfortunately it depends on the gearbox design how little - but as a rule of thumb, more than one, maybe two tenths of a millimeter is a problem.

And yes if the Ferrari guys are of the "thinking along" variety, then by all means ask for their opinion. I am a bit biased against garages as in my experience a lot of them are a waste of time and money when things become more difficult, it showed in my opinion.
They know these cars and may even say "they all do that, don't worry about it".

 

OOOOHHH!!!!

That's not good.

Well at least you caught it before it got worse.

 

wow great catch, how many miles on that trans?

 

*1

And did you find any bits in the trans oil or on the drain plug?

 

That's nasty! Any damage to the driven gear on the diff?

 

Ouch. Expensive. It looks like that gear chewed on something. Could be on its own metal bits or possibly the same issue Ernie mentioned in this thread he had with his box, failed bearing cage.