Due to unforturnate circumstances I have to make my boo my daily driver. Well after picking it up from the muffler shop today I noticed it would start vibrating when I get above 3k rpms. Now when I did the swap I did use the fly wheel from the 2.8 on the 3.4. Would this cause issue? It wasn't doing it before I took it to the shop ( but it didn't have much power either because of the bad leak it had). Now the reason for using that flywheel was I had just got it turned and trued so it seemed like a good idea.

I don't have a clue what it could be but as long as I don't hurt nothing till next weekend so I can really get into it.

Thanks for the feed back in advance!

 

well i had the same problem i really cant remeber wut year they chand from external to internal balance but you probably have a externaly balance flywheel on the 3.4 switch it and it should fix ur problem to check pull off ur inspection cover and see if it has weghts on the back if not then u got me stumped

 

Hopefully thats not the case. I found this site that states the 2.8- 3.4 are nutrally balanced.

http://www.s-series.org/htm/tech/GMP...ts/144-148.pdf

I hope this is the case and its something more simple.

 

OK I may have answered my own question by reading a lil further. This is what I found:

The 3.4L is an internally balanced engine and comes with a standard 3-hole flexplate. The problem for me arose when I realized my 904 transmission required a 4-hole flexplate, but the 3.4L required a balanced flexplate.

Some points:



The 2.8L is an externally balanced engine, requiring the flexplate to be heavy weighted to one side.
The spacing between the engine and the bell housing will be increased up to 1/2" if the new flexplate is used. (I drilled four holes in the new flexplate and tried to assemble it without luck.)
They DON'T make a flexplate for the 904 transmission that is neutrally balanced.

So I guess I have some work ahead of me.

 

Mine does the same thing, but I know my engine is pretty much stock except for my intake. Things have been replaced like alternator, starter, dist. cap, plugs and all basic stuff, but ever since I've had it when it gets right around 3000rpm it starts to vibrate. I noticed if I'm accelerating faster though it seems to sort of 'power through it'. It just does it if it sits around 3000 for a second or two