I got the new trans installed the other weekend and went for a drive and...the vibrations are still there.
I guess we've eliminated one more possibility= the trans. So, it seems the issue is somewhere between the front of the engine and forward of the trans.
I've been reading various vibration threads and I'm wondering if the vibration is a result of a physical imbalance (i.e.- internal rotating assembly out of balance, flywheel counterweight incorrect) or an imbalance related to tuning (i.e.- misfire, incorrect timing, etc)?
Wouldn't a physical imbalance begin to vibrate at a certain RPM and continue to increase in severity through the RPM range?
In an effort to be concise, I'm going throw out some facts from what I know at this point:
-Vibration is not speed related.
-Vibration occurs around 1900-2100 RPM's, then goes away and returns around 4000 plus.
-Vibration decreases when I push the clutch in and engine speed begins to drop.
-Vibration seems load dependent.
-Vibration isn't noticeable/present when engine rev'd in neutral at a standstill.
-Engine seems to have normal water temp, oil PSI, power.
-Engine DOES have run-on/dieseling when I shut off the ignition. Usually around 3 seconds of continued rough idle before finally dying.
Regarding physical imbalance- I ordered a few different flywheel counterweights and was planning on trying to find a counterweight "sweet spot" via trial and error. Someone mentioned that the rotating assembly could have originally been balanced with the flexplate that came with the engine and now that I've installed a flywheel, it could be out of balance.
On a positive note, I did get around to making some valance opening inserts to match my grill...