cster

MY06 STI
When I am on full boost 2500 to 4000 RPM, I am getting severe juddering/tramping from the rear end.
It is worst in 6th gear as it seems to spend longer on boost in this gear.
In fifth it is less of a problem and even less so in fourth.
In second and third gear, it seems to accelerate through this rev band too quickly to cause the juddering.
These symptoms lead me to believe there is a harmonic aspect to the juddering, but I basically am perplexed.
Any ideas?
The engine has recently been taken out for head gaskets and some mods were made to the exhaust system that have increased torque out put.
Coincidentally there has been an increase in NVH between 1500 and 2000 RPM since the work was carried out.

c_maguire

Have you considered it may be rear diff or bush/strut/linkage related?

Kevin

cster

I have thinking along those lines. Might have to get under-eath with a cro-bar or something.
I don't want to throw money at the problem as I spent a fair bit on the Gaskets.
If I can get a clear diagnosis, I don't mind coughing up - for the moment I can drive around the problem by staying above 4,000 when on full throttle.
Fuel economy has gone to **** though.
Cheers for your help.

prodriverules

iTrader: (52)

Rear end judder on full boost.
yeah thats your bum twiching

f4la k

iTrader: (1)

What mods were made to the exhaust system when the engine was out. Was the car remapped for the mods. Was the correct thickness of headgasket used to keep the comp ratio the same.

Does the car still select gears easy as it might be a flywheel or clutch vibration.

cster

Decat, ported headers and larger cross section up-pipe were the mods.
Then mapped by JGM.
I think I have gone about that in more or less the right order (hopefully).
I had the clutch replaced with an Exceedy pink 240 mm jobby and the gearbox remains as sweet as the proverbial nut.
The heads were skimmed with an increased thickness HG, and it pulls like f*ck.
I have always been a little bit suspicious about the rear end, as it has been a little bit "knocky" under full throttle in first gear when turning. It may well be that the torque increasing mods have served to highlight a previously inherent Achilles heel if you take my meaning.
Again, thanks for your inputs and I will definitely be having a closer look at the rear assembly.