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Altezza Club Of NZ/Australia > Driveline - Clutch | Gearbox | Differentials > An Answer To The Gearbox Noises Mystery?


Title: An Answer To The Gearbox Noises Mystery?


roman - June 15, 2009 01:17 PM (GMT)
The Altezza 6 speed box is a unit made by AISN called the AZ6.

This same design is used for the Altezza, S2K, S15, MX5, and RX8.

So, doing a quick search for noisy S15 gearboxes, turns out that they exibit the same symptoms as the Altezza boxes, noisy in 5th/6th, noisy at 3000rpm, etc.

Which is no surprise, but it seems as though someone has figured out why!

QUOTE

There is nothing wrong with the 6 speed as myself and fergo mentioned way back in this thread.

The common issue with them is the circlip/snap ring breaks out of the groove and causes all sorts of shift problems. The fix there is to machine the groove deeper and provide the ring more surface area to but up against.
Syncro failures are not common nor are gear set failures.

The noise you hear through an S15 box is very common and was acknoledged by nissan in the early stages however few were fixed as the noise was at the time demed to be acceptable for a sports car.
The problem has been identified as the front two constant mesh gears. The input shaft and the lay shaft's both have a fixed gear that like to become noisy in the teeth over time. The biggest cause seems to be poor lubrication/oil quality.
I have seen dealers replacing bearings, thrust bearings, spigot bushes etc etc however of all the boxes I have seen pulled down they all display the same or very similar wear markings on the gear faces.
Replacing the gears and using a good quality oil will fix the noisy box issue. Its not nessisary to overhaul the box just to replace the gears. You can get away with just replacing the parts that are worn. Typically syncro's and majority of the bearings are re-usable.

Leiden - June 16, 2009 05:45 AM (GMT)
Gears probably aren't cheap though, I bet this is whats happened to my box, stupid Castrol VMX.

E910 - June 16, 2009 06:54 AM (GMT)

turbo tezza - June 16, 2009 09:46 PM (GMT)
QUOTE (E910 @ Jun 16 2009, 06:54 PM)
RedLine MT-90 FTW!!

Thats what I have been running in my gearbox for about 5 years - and it seems to be holding up fine behind the turbo power ^_^

Corey

Outlander - June 24, 2009 10:23 AM (GMT)
I knew there was a reason other than me simply being pedantic about the noise haha! And also confirms my suspicions that the Gearbox is the same as the S15's.

I though Borg-Werner made the Gearbox though?

Leiden - June 24, 2009 11:54 AM (GMT)
The 6 speed is built by Aisin, I think Borg-Warner did the T50 series box found behind rwd 4AGE's




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