you are right sir. i apologize for the miss use of terminology. i have experienced u-joint angle vibrations with around 4 degrees of operating angle difference. different cars and trucks seem to have different sensitivity. you measure the operating angles with an angle finder. there are free apps on smart phones for angle finders. you need to measure the angle that the center line of the motor and trans points and the angle the differential points. the differential should be pointed 2 degrees lower than the motor/trans. this allows for it to walk up the 2 degrees under power to bring the u joints into phase. check this page out http://www.hotrodhotline.com/md/html/drive_shaft_harmonics.php
That really doesn't mean squat! I've had brand new tires that couldn't be balanced, or that would change balance after a few hundred miles! Also, I've had brand new rims that were off center and had to be replaced! The main difference ( IMO ) between tire, wheel balance and a drivetrain balance, is that tire, wheel balance is more of a thumping imbalance as compared to drivetrain, which is more of a " buzzing " kind of vibration.
I would say you're on the right track if it is only present at a given ground speed it's drive train related. If it were an engine balance issue it would be relative to engine speed and happen in every gear if you reach the magical RPM.
I discovered today the flywheel has an extrange counterweight. We put a new flywheel and the car vibrate a lot. I need to check the u joints angles but something make me things they have problems. Thanks for the info is very usefull for me.
sounds like you mixed up the 28 ounce crank of the early motors with the 50 oz external weight of the later 80's motors. The harmonic balancers are weighted different as well.. so check that first if you swapped that too. PS.. do NOT run that motor like that as you will take out the bearings fairly quickly.
