2001 deville shifting problems

Almost a sure bet you've lost one of your shift solenoids (2nd and 4th). Common problem, not too bad to fix but you do have to drop the pan and the valve body. GM sells a kit with the updated solenoids and improved bracket.

Here's a how-to with pictures: http://www.cadillacforums.com/forum...85-code-p094-shift-solenoid-speed-sensor.html

It should have set a code, have you looked at what codes were stored?

P1845 - 2-3 Shift Solenoid Circuit Low Voltage

I don't know with it being a history code, but your problem of missing 2nd and 4th does not sound anything like a VSS problem. Does your speedometer still indicate correctly? It sounds like the textbook definition of the shift solenoid failure. I don't know about the solenoid interchange between years, but I'd just get 2 of the updated ones from GM and replace them both. I can't find the info at the moment, but I know those 2 solenoids control all gears. The different on/off combination of solenoids A and B give you 4 forward gears.

I hope that's all it is, sure sounds like the shift solenoids. Not sure about the rpm drop--900 rpm is awfully low (more like the trans is going into neutral... ). Could simply be because the trans is not locking the TCC, it won't do that in 3rd gear, and probably also won't when there are other issues with the transmission.