We want to go from CDG to Nancy via train. A good option is RER from CDG to Paris Nord and TGV from Paris Est to Nancy. Issue: the connect time is 30 minutes but there is an 800 meter walk between Nord and Est which the site says takes 37 min. Usually we could walk 800 m in much less than 30 min, but this will be after an all-night flight with awkward wheelies and unfamiliarity with the place. Do experts think it would really take 37 min? Would a taxi even consider such a short trip? is there a bus or shuttle? Thanks in advance.

You can go direct from CDG to Lorraine on the TGV and connect with a bus to Nancy. Takes about 2 hours.

You should be able to do the walk in 10-12 minutes or less. You walk down Rue de Saint-Quentin, and left of Blvd de Magenta. You'll see the station once you reach rue Faubourg-St Dennis. Or you can walk straight down Rue de Dunkerque and right on d'Alsace. It's hard to miss.

I agree. But there's no need to spend the money or time to go into Paris at all.

I'm not clear on where you saw that 37 minutes time, but on ratp.fr they say it takes 46 minutes for the total trip (RER from CDG to Gare du Nord, plus the walk, for the time of day I picked), so that wouldn't make sense for the walk alone to take 37 minutes on their website. So, no, I wouldn't expect it.

A taxi is not going to want to do that route, absolutely not. I had one refuse me once at Montparnasse for a trip longer than that, even though in theory they are not allowed to do that.

Thanks to all for good advice/info.

The 37 minutes sounds more like a total trip time to me. It is a 25 to 30 minute train ride to CDG and about a 10 minute walk for most people station to station or about a 5 minute metro ride on lines 4 or 5.