Post by
amc49 »
https://forums.nicoclub.com/amc49-u275146.html
Wed Aug 02, 2017 9:05 pm
If talking about a vibration that seems to increase to hit a high then drop back off over and over look at your mounts, may be engine instead. A harmonic that lines up just right in the unibody to show up at a very tight speed and spread. If you can drop a gear for just a few seconds and check same speed it might tell you something, tires still going same speed but engine not then. Would then point at engine.
Start seeing if any different throttle inputs can affect it too.
Often aftermarket mounts can make things like that worse, the aftermarket in no way makes the diverse numbers of rubber compounds they used to like the OEMs, commonly they are rock hard now and new mounts can be as bad or even worse than old original ones. What we got with things Chinese. Like the utterly crap alternators and starters we get now. The companies have a stranglehold on things like that now and crap is all you can get period.
Look at tire trueness by spinning them, out-of-round can do it too and no balancing on the planet can touch that. A slightly bent wheel could do it.
If anyone has used like Fix-a-Flat in the tires that can do it too, the extra fluid moves around to balance then unbalance the tires in a recurring harmonic and I've seen it be very speed related in a tight pattern before.