Volvo: 850 transmission probem, volvo 850, gear shift

Question
First gear in my '93 Volvo 850 sometimes doesn't engage, especially when slowing down quickly from a freeway off- ramp. The gear shift is in D but it acts like it is in neutral. Sometimes it will SLAM into gear by itself after a few seconds, or if I rev the engine a little. But if I pull the gear shift lever down into first gear when it is slipping, the transmission will ALWAYS go into first gear and not slip. Do you think the problem is electrical, not mechanical? Could it be the PNP switch or speed sensor? Thanks for any advise. Jim.

Answer
Jim,
There have been quite a few failures with the PNP sensor, and that will cause your problem. Have the codes for the trans control unit read and see if anything indicates the PNP switch. You may also want to just have the PNP replaced.
Since the vehicle does go into first gear manually I would say your problem is elcetrical.