Any thoughts?

[Bryan]

Hey guys! I picked up my bus from the shop right as they closed last night. Had to get s new alternator. Anyway, they are closed for the weekend, and it seems I will be taking it back to them, because of something new I'm noticing on the way home.

There is a shaking/vibration type situation going on. It almost feels like hitting little bumps on the road consistently. For example like the bumps they put on the side of the interstate to alert you if you run off, except not near as loud or severe, but same feeling. I want to clarify the shaking isn't huge, but definitely noticeable and something I've never felt before.

As long as my foot is even slightly pressing the gas pedal, the shaking goes away. The shaking only happens when you are coasting, but even the slightest little press on the gas pedal and it goes back to running smooth. As this process happened, I watched all of my gauges to look for unusual activity.

I want to talk about the turbo boost PSI gauge. What I'm about to describe may be totally normal, but maybe it will help explain the situation. If I'm cruising with my foot barely pressing the gas pedal (smooth ride) and the Turbo is at 0psi, as soon as I let off the gas pedal, it will increase to 5psi (and shake), then when I slightly press the gas pedal it returns on 0psi(back to smooth)... seems backwards to me, but maybe it's not... Now of course if I press the gas pedal harder, the PSI increases more and more a lot higher than 5psi.

Now I want to talk about the transmission panel in this matter. There seems to be a shift that happens in the middle of second gear, it's almost like 2nd gear has 2 gears with in it just by the way it feels so I'm going to call the gears 2 and 2.5 for the sake of this conversation. If I'm coasting with no gas pedal, feeling the shake, while boost is at 5psi and I let it coast all the way to a stop, it will shake all the way down from gear 6 to 5 to 4 to 3 to 2.5... but in the middle of 2, it will stop shaking and at this time the boost also returns to 0psi.

One last thing to note... when I got home, the person following me said that she heard some unusual noises in which she described as sounding similar to jake brake type noise. Of course my bus does not have jake brakes, but she described the sound to be similar to a truck slowing down with jake brakes.

Any thoughts?

[robertglines1]

which bus?

[Bryan]

Oooops the Prevost

[Timkar]

From your first few lines, I would check driveshaft and U joints

[niles500]

The 'extra' gear in 2nd is the torque converter lockup, boost gauge could be wiring, sender, sensor ...

[eagle19952]

sounds u-jointy/diffy to me too 

[DoubleEagle]

Looks like everybody has nailed it, end of thread? 

[luvrbus]

I forgot what transmission is in the bus the B500 is a total different animal than the 700 series

[Bryan]

It's a b500