Report "I have an Isuzu Trooper, 1996, manual tranny. I have the axel (vacuum) engaged 4 wheel drive system (not the hub auto lockers) and shifter lever to engage 4 wheel drive. My 4 wheel drive is getting slower and slower to engage. I drive sometimes 5 miles or more before the light comes on showing engaged (switch on axle was replaced, wiring & switch appear correct). I have also noticed that if I switch off the car for 15 mins or more, like going for a lunch, when i start and drive away, the 4 wheel engages about immidiately if left in 4 wheel drive. Drive around in 2 wheel mode for a while and the thing gets doggone slow engaging again. I can tell it is not engaged as I have no problems making sharp turns in a parking lot, yet the whine increase makes me believe that at least the shifter lever engages the forward drive shaft"