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rpm related vibration issue

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cudadrt

15+ Year Contributor
110
16
May 9, 2008
Maryville, Tennessee
I've searched constantly on this site and many others with no luck. I just rebuilt and installed a 6 bolt engine into my 2g. Everything was good and fine until last week when I started to get an awful vibration around 3k rpms. Motor has just under 1k makes on it. Everything I've found on this matter has been related to the balance shafts. I've eliminated that possibility since I installed a bs elimination kit on the rebuild. It'll start around 3k rpms and go away above about 4500rpms. Out does this in all gears and sitting still in neutral. I've checked the motor mounts, transfer case and transmission for looseness, and I have run out of ideas. I read one response from someone who claimed to have had this problem and they said they redlined it to 7500 through 1st and 2nd and it went away. That'll be my last resort as I'd rather fix it correctly and not chance something catastrophic. Thanks inn advance for any and all help. Below is a little info about the build.

95 tsi awd
Full 6 bolt swap
Hks 272 cams
2g pistons on 1g rods
ACT 2600 with sprung 6 puck on stock flywheel
Gm maf
Dsmlink
18psi boost
 
Hard to determine what excessive vibration is over the internet. Removing the balance shafts will cause vibration at about the RPM range you mentioned. Whether it is the normal vibration those of us without balance shafts have or if its more than what we're used to is the question. Do you have anyone with a car that has had the balance shafts removed that you can compare your vibration against. If you aren't used to not running balance shafts it can be a little annoying until you get used to it.
 
I did not remove the front bs...... just the rear but left the front bs belt off it. Have several friends running their car like this with the bs and no issues like I'm experiencing.



This is not normal vibration as I did a bs elimination on my previous 7 bolt and vibration was almost unnoticeable...... unless the 6 bolt has a bit more vibration. It's harsh enough you can feel it through the seats......... like when you run over the cut outs that are in the emergency lane of the highways....... sounds the same as well when it does it. If nothing elsel I'll put another motor together and try it to possibly rule that out.Going to drop the tranny this weekend just to make sure it isn't something clutch related. Thanks for the replies.
 
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