I used to know a family that owned a cabin at Tabor Lake. I had heard from them many, many times about a RR car in the lake. They say you can see the wheels under the water along the tracks from a boat. I heard this from them all through the time I knew them from the late 70's into the 90's. Other people I know also swear there is a RR car in the lake also. We drank and partied at Tabor Lake quite a bit back in the day. I once knew several of the people who spend summers there and they all said it's true.
Weather this is in fact true or not, I don't know. There was once an Ice house along the lake so it may be an old Ice reefer. There is also trolley ROW remains near the road crossing at Tabor Lake, and it goes all the way down to Rt 10.
Tabor Lake is not by Mt. Tabor station. It is 2 miles or so from it. There is another lake between Mt. Tabor and Tabor Lake. This one we used call "Chettles Pond" while we were growing up. The real name was Lake Lenoir. I have no idea where these two names came from. Some maps get these two confused while others call one or the other Powder Mill Pond. There was once a Powder Mill built along the outlet of Tabor Lake. The water leaving the lake ran the mill. This is where that part of Parsippany got it's name from.
There is a web site about Tabor Lake here:
It doesn't say anything about a RR car in the water though. I just E Mailed the site admin asking about this rumor. I'll let you know if I get a reply.