Sorry for the bad tip. All the digital Tascams I've used had MIDI.
I have other solutions for you. Go ahead and record on both machines using four inputs. Since you have to start recording manually, they won't be synched. Export the tracks from both machines onto a computer, and use editing software to match them up. Don't move one of the machine's tracks and make the other one's match up. Then import them onto the machine you didn't move the tracks from and they will match. (By "move" I mean editing, moving the track in time, not exporting the track, which is "moving" it from one machine to the other.
This can be made really easy by having some kind of count before the song starts, such as four stick hits.
I use Audacity, which is free, to edit tracks like that.
An update on synching my DP-01 and 2488neo--it didn't work. I'm really sure I had all the settings correct, and Tascam support told me that I could indeed get the transport of one machine to control the other, but no luck at all. It would've been neat to do. perhaps the MIDI doesn't work on my DP-01; it's older and I bought it used and I've never used MIDI before on it.
I'll let everyone know if I ever get it to work.