Banging sound on acceleration in 4th gear up

[hnnrs]

Hi,

Newbie to forum here, please bear with me... I have a 2004 roadster which has served me well with just under 130,000 miles so far. Unfortunately the other day I heard a knocking sound (bang,bang,bang etc) on going into 4th gear, made worse on acceleration, to the point I couldn't accelerate. Reverse, 1st, 2nd & 3rd gear were OK. Horrible journey home from work - over an hour. I've read that the gearbox never gives trouble but I was wondering if the gearbox has gone or some other factor might be causing the banging noise. Any advice would be appreciated before I look for a second hand gearbox replacement.
Many thanks.

[Thrumbleux]

Boxes are tough - wiring is weak.
The shift to 4th requires more work from the gearchange selector motor as it has to shift the final drive as well as selecting the lowest of the ratios within the box. Frayed wiring/poor connections have identified themselves before now by being awkward to make the shift into 4th.

[hnnrs]

Thank you. I will look into the wiring & gear change motor.

[Thrumbleux]

Typically, the wiring gets chaffed rubbing against the intercooler air scoop.

[10:45PM]

Search for 'chafed' on fq101.co.uk

[137699]

I seriously doubt this is chaffed wiring. Whilst an electrical fault would cause the gears to be difficult/impossible to select, they won't cause a knocking/banging problem.
The gearbox *could* be at fault. It's incredibly rare but you would not be the first.
The clutch actuator could also be another cause - especially if it's not had a re-teach for a while.
My personal opinion is that it may well be the spiders-web drive plate that connects the clutch has sheared in the centre. Becoming a fairly common issue and if you buy a new one from smart you will see it's a new stronger design now.

Gearbox out to replace it though.

[Thrumbleux]

I seriously doubt this is chaffed wiring. Whilst an electrical fault would cause the gears to be difficult/impossible to select, they won't cause a knocking/banging problem.

It will bang and clang trying to select 1st gear at standstill if the clutch actuator is goosed - had that happen on mine.
.

I The clutch actuator could also be another cause - especially if it's not had a re-teach for a while.

If the CA isn't up to snuff - then it appears it is only affecting the OP on selecting 4th gear. Hard to imagine the extra electrical load of the shift to 4th knocking the CA out, but it is a smart...

I My personal opinion is that it may well be the spiders-web drive plate that connects the clutch has sheared in the centre. Becoming a fairly common issue and if you buy a new one from smart you will see it's a new stronger design now.

Gearbox out to replace it though.

Sounds the most plausible explanation.

[janseb88]

Were you able to confirm that the wiring is the problem?