Differential Noise ?

My wife was in a nasty accident recently with our trusty 1990 Burb and it saved her life, but it had to give it's life in return. Now it's sleeping with the angles. We just bought a nice 1999 4WD LT Burb with 96K to replace it, but it has a couple of problem areas that I thought you guys may know something about.

Three of the electric door locks no longer work. The PO gave me new actuators to install, but it seems odd to me that 3 of them would go out. Are these a common failure item ?

When I idle the car I hear a high pitch whine on the outside/rear of the car that the PO says is the fuel pump in the tank. Is it common for these to make a rather loud whine ?

When driving along in 2WD I notice that there is a gear messing sound (gear whine) coming from somewhere behind the front seats, (hard to tell exactly where). On flat payment it seems to be there while gas is applied, but when I let off I hear it pulsate on and off more like the sound a large standard transmission makes, not an automatic. I haven't checked the fluid levels in the rear end or transfer case yet, but wondered if this noise is normal, or if it is an indication of a problem.

Thanks for any help.

Just bought a '99 LT 1500 4wd as well, mine has 48k miles, (lucky find), but the same symptons as follows:

1 door lock actuator will only lock not unlock, the rest are working normal for now - have heard this come up quite a bit.

Fuel pump is a lot louder compared to my new body style pickup - I changed my fuel filter and feel it is operating normally, this is also a hot topic on this forum, they do tend to go out more frequently than other's from what I've read here, but usually if the person isn't staying on top of the fuel filter changes.

I can hear gear noise - I just stay on top of fluid changes and check things regularly (u-joints, driveline play, etc.)

So not that I had any real useful info for you; just thought I would give you the comfort that the same vehicle with less miles has similar "traits". If you haven't already just change all your fluids and keep your ears open for any changes down the road. (In my opnion)

door lock actuators go out all the time in these things. as for locking but not unlocking either the switch is bad (if the pass switch will unlock) or the relay is bad( if it has keyless entry). i wouldn't worry too much about the fuel pump just change the filter regularly. gear whine / diff howl is fairly common on subs. if the whine is excessive the pinion bearings might be worn(try moving the yoke up & down).

amac: I can see my one bad door lock try to unlock but it is like it doesn't have enough umph. Relay or is there something in there I can fiddle with that might bring it back to life. It hasn't bothered me enough to try anything yet because it is the driver side passenger door and just as easy to reach in and unlock myself.

Thanks.

you have to remove the door pannel and replace the actuator. not too big of a job. to remove the door pannel remove the 2 screws in the handle, pop out the trim around the door locks then the pannel will need to be pried straight out. there are a bunch of pull out fasteners in the pannel. you will need a good prying tool, keep prying around the pannel untill it is free. there is a sheet metal plate screwed to the door which holds the actuator linkage. remove the screws around the plate so it can be pried out enough to get your hands behind it. the actuator is held in by pop rivets.
have fun!