Jack position 1988 - 1989 Buick Park Avenue

try this ... make sure the switch is in the 4X4 position ... drive a few feet (20-50) while moving slip the truck into neutral then flip the switch to 2 wheel. if does not work try the same trick in reverse..
The pressure on the drive train must be relaxed for the truck to shift...
you can try jacking on side up as well (two wheels)

Stand in front of the car,open the hood and at the 2 o'clock position look down between the rad and the engine.You will see it better from under the car.

Either Jack up the engine off the block or sump BOLTS block of wood between Jack and sump or lift it with an overhead crane, block and tackle ext, be careful with fan clearence when moving engine...

There's an easy way and a hard way. You can drop the tank (one bolt on each of two straps). Make sure you support the tank with a floor jack and let it down easy so you don't break the fuel lines. Or, you can disconnect the fuel line at the fuel filter, put a pail under the line, and turn the ignition to the on position. You'd have to do it a few times as the pump will only turn on for a little while. If you're draining it because there's liquid in there that shouldn't be (i.e. diesel), you can do it with the pump. If there's rust or foreign obecjts in there, drop the tank.

put a jack under the front of the motor, take off the motor mount and lower the jack to rock the motor forward to allow for extra room, be sure not to jack up the oil pan and put a board on the jack to protect the motor from damage

For 1988, there you have several sub-model:
Volvo 240
Volvo 740
Volvo 760

Generally, the tool kit and jack are under the carpet in the cargo space floor, next to the spare wheel.

This LINK is just for reference, but if you can register for acces, maybe can find the owners manual in there.

Hope helps with this (remember rated) Good luck.

First unhook pos. battery cable at battery, next unhook cable on starter selonoid and small wire on selonoid, next craw under car (you may have to jack up car and support it with jack stands) remove inspection cover on flywheel then the 2 bolts that hold starter in and thats it starter will come out.

Normally you put a floor jack under the engine front or flywheel with a 2x6 cushion board attached and jack it up an inch or so to releave the pressure on the motor mount. Then with mechanic tools and wrenchs remove and replace the motor mount.

I usually jack up the car and use a pair of jumper cables. Connect the red cable to the starter lead that the battery cable attaches to and the black cable to any good body ground. Connect the other ends of the jumper cables to a good hot battery. Use jack stands for saftey reasons. Be careful and good luck. It always works for me.

Look under the vehicle, between the engine & the transmission. You can't see it from on top.