Inadvertently exceeded driveshaft "Critical Speed" at Willow Springs.

jos51700 said
I was thinking about this on the way to work this morning. I've had my Dakota to 120, and it's wore the hell out, with overdrive and 3.55's. No shake.
How are you certain that isn't a tire issue?
NOT doubting, just wondering if you've somehow eliminated these as the source of the problem. Remember, is almost impossible to get something perfectly balanced, we just balance tires and wheels to be in balance below certain thresholds. It's easy to spit a weight at that speed.
Additionally, are you sure your tires are speed rated? Tires do funny funny stuff when pushed up too those speeds and the drive shaft sure sounds straight and balanced. (It is straight, right? It can be bent and still be balanced at certain speeds)
Forgive me if you covered that and I missed it.

I appreciate the input. No apologies necessary. Tires can always get knocked out of balance or throw a weight. My rear tires are rated at 186 mph, the fronts are rated to 146 mph; so they should take it. I had them rebalanced just before the trip down to LA and they were smooth as silk the whole trip.

A few months earlier, I had a rear wheel bearing go bad on the passenger side. That vibration seemed like a drive line vibration at normal freeway speeds. That's when I had the driveshaft double checked. Strange built the driveshaft and stated this morning that it has a critical speed of 7000 rpm, but take away 20% as a safety margin. That's only 5600 rpm.

What is the overdrive ratio on your overdrive, and what rpm were you spinning at 120 mph?

The sensation of the vibration is