I have a Formula 350 with about 50k miles on it and i noticed that if i break 75mph on the highway in OD suddenly the ride gets oddly "rough". Like, there is some sort of slight shutter/shake that i can feel through the front end. What's strange is that if i drop it down into regular Drive and maintain the same speed everything smooths right out. Any thoughts?

 

You've probably got a fuel-delivery or ignition problem.

 

really? those types of things could cause issues with just overdrive? Thanks for the tip.

 

I'm not an expert, but I think the idea is that in OD at 75MPH, the engine isn't turning all that many RPM's. If your rear is 2.73 and the transmission is in OD (I seem to remember that is a 0.7:1 ratio), the engine could be "lugging".

Although it should run efficiently at this setup (assuming vehicle in perfect working order), it isn't making a whole lot of torque. Therefore, if the fuel delivery or ignition components aren't up to snuff, you can experience similar problems as you describe. For instance, even a slight grade increase in the roadway, or a sudden headwind can cause stuttering.