Knocking sound when revving in gear 2/3

[ccmengs]

Hey guys i've got a eg5 vti, i had a gearbox rebuilt to replace the bearings a couple of months ago because it was making noises, i can only hear the noise if i wind down the passenger window, sometimes i can hear it from the driver side window too.
recently when ive been driving theres this weird 'knocking' or 'clunking' sound (can't really explain it), especially when the car is travelling at like 5-10km/h and i chuck it into gear two and rev it (sounds like it's struggling).
i've notice that it only happens when im over revving in high gears, but sometimes even in gear 1 i can hear it, could it possibly be the gearbox bearings again?
i can't remember what it sounded like the first time, just wanted your guys opinions before i take it out the the mechanics again incase they might make up some problems lol coz ive still got 12months warranty on the gearbox rebuild.

oh i forgot to mention, i recently downgraded from 17" to 15" rims, maybe this could be the problem?

cheers

[quangsuke]

if you have a aftermarket filter it could be from that. just putting ideas out for ya

[bennjamin]

sounds like you are lugging / over loading the engine for the gear selected , and the noise is pinging ( pre ignition)

[Chriskoss]

Sounds to me like ignition/spark. If car is struggling to get power from low speed + rpm you may have weak spark, car will struggle to accelerate rapidly and or die. Check spark plugs, distributor, ignition coil, igniter, spark leads.. then you can go from there
The engine will make a knocking sort of sound if its not getting a good spark or something is interferring with the spark, maybe your timing is out?

[chowdaa]

what exactly is occurring within the engine due low spark to make a knock? im with bennjamin on this one for sure. from what you are describing because you are using a high gear you are loading up the engine causing pinging. Only aspect of ignition that is relevant to pinging is the ignition timing which would correct your problem simply by retarding your timing and having a more controlled burn time in your combustion process. google "detonation" or "pre-ignition". The noise didn't happen straight after the build right? retard your ignition timing and if the noise is gone you are on the right track

[ccmengs]

ah ok but sometimes i can hear it in gear one when im accelerating from rest and sometimes the noise is not even there. perhaps i should replace the spark plugs? my eg has done 223xxx km :P can anyone give me an idea of how much would it be to replace timing belt and spark plugs etc?

[chowdaa]

It is easy enough to reset timing but its your car. For a gates around 130 for the belt, plugs are 4.50 each for copper NGK. plugs i am sure you can do, the timing belt has a few hours involved.

[ccmengs]

thanks for the replies guys :) very much appreciate it

[CTR_EK9]

try using higher octane and see if thats works first