Legacy question!!

Doesn't matter what gauge. But I would use #18 or so. It carries a low current 455KHz signal to the track...about 6 volts peak to peak. Just connect it to the U terminal of your transformer which goes to the outside rails of the Fastrack.

Just get a the piece of wire, twist the ends, and secure under the Legacy base binding post and the transformer "U" binding post.  Your done.

Yes. Just connect the terminal track black wire and the Legacy Base black wire both to the same GW-180 U terminal.

Lionel should have included the black wire to connect the Legacy base to the track. What would it cost them? 99 cents?

I used the black wire from a spare Fastrack terminal track.

Connecting the Legacy base to the track is perhaps the simplest and easiest aspect of setting up the Legacy system. 

It works either way. As as long as the Legacy wire goes to the common (U post) and that common wire connects to the outside rail, the signal will reach the track

It is electrically the same point.

Is anything in addition to the 990 and connector wire needed to operate conventional locomotives?

What is your power source?

CW-80 or PWC ZW with two 135w bricks.

If you use the PWC ZW you should be good. You might want to pull out that manual. 

Also so there was an issue with some ZWCs that Legacy exposed. You can read about it here.  It doesn't affect all. 

Please note that most folks can change the chip without disassembly. 

Thanks for the informative reply, MartyE.

Just take the cover off of your ZW-C. You can then see the chip and check the lettering for ZWPC S01.HEX. If it's labeled with that, it's been changed and you are good to go.

I have an older ZW It will be hooked up to 4 separate blocks on the track, Question? do I have to hook the command base to each U post or will one connect to all the commons?

They are bussed internally.

Andrew;

From the Legacy manual page 12.

Address Your Engine
First, you must address the engine. This “tells” your CAB-2 which locomotive you want to control. This is important when you have more than one engine on your layout.
NOTE: CAB-2 will revert to CAB-1 mode for any engine, train or accessory UNLESS you enter the options for that addressed unit either manually or with a memory module. (See page 46 or page 74 respectively)

Andrew look on the other thread you asked this same question for an answer I posted

Please try to limit your questions to one thread instead of posting the same question to several , it makes it easier to help