[ApoelAlex]

The gearbox seems to humming a bit from 1st to 3rd gear so am asking...

Car has 84k miles...

What's the maximum torque the 320d manual gearbox can handle? Been running a map for 3 years now and I think the problem is because of the mod...

Keep in mind am changing gearbox oil every year

[bmwak]

You'll need to give some indication on what map/power and torque output your running. What engine M47 or N47?

[ApoelAlex]

it's the N47 engine... No timing chain issues here...

The map is a custom one.... power is 217 hp with 450 torque

[ApoelAlex]

I have just checked with zf website, says max torque is 370... wtf?

[PaddyMcGrath]

Sounds right but you should be able to confirm it from the part number. For example mine is: GS6-37DZ - THES

GS6 (Manual 6 Speed) - 37 (370Nm) D (Diesel) Z (ZF)

It basically means that the gearbox should survive its lifetime with 370Nm and anything over that will shorten its life span.

[ApoelAlex]

the map is off then.... just to be on the safe side...

even though the gearbox could already be damaged.....

[bmwak]

Yep you need to establish what gearbox you have exactly.

The N47 Engine has several variants. The 184ps has 380nm of torque, so would be capable of more.

Also worth seeing the torque output of the official BMW performance map. Edit: the Performance map torque output is 390nm (for 177ps). If yours is 177ps too, I think your torque output is probably too much for your GB to handle. Maybe worth downtuning but as you say, damage might be already done.

[dj219957]

seems odd then that the emaps and end tune maps advertise 425nm. there must be lots of "happy" (for now) customers running these tunes.

[PaddyMcGrath]

Just because a gearbox is rated at 370Nm, doesn't mean it's going to catastrophically explode with anything over that. Although, the further you go above the recommended torque, the more likely you are to find yourself in trouble in the future. If your 'box is already dead, why not keep your map and source a 330D box? They're rated for around 600Nm

[Digitalize]

Would a 330D box even fit? Completely different engine.

[E91-Gaz]

Are the 1 series boxes interchangeable? If so 123d box must be a good option as the 123d is still an n47 engine with about 400Nm as standard IRC?

[PaddyMcGrath]

123D uses the same gearbox as the 330D (GS6-53DZ) so should be a direct fit, but would probably need a custom prop shaft (along with a new clutch & DMF).