I haven't seen the "axle lock" (actually a half shaft disconnect) used on FWD vehicles for quite awhile. REMCO had them and presumably others.
The Frontier, as an RWD truck, is a different animal. Only manual shift versions are towable. What? You say. Put the 4WD transfer case in N and go. Nope: No Neutral in the Frontier's TC. 2WD manuals tow in N and 4WD tow in N with the TC in 2WD-High.
We tow a 2009 4-cyl 5-speed manual Frontier. Great truck, but we want manual transmissions anyway.
An OP here on RV.net wanted a Tacoma and to be able to tow it four-down. Went Driveshaft Disconnect and hated it. Traded trucks to get out of it.
The things DO work. The problem seems to be they're temperamental about the connect/disconnect routine. I'd want a spare driveshaft as noted above.
Might be a REMCO lube pump for 2WD Frontier with automatic. Many use pumps OK. Others have had transmission failure and grief with Warranty, REMCO, etc.
I don't like the trucks but perhaps the GM Chevy Colorado/GMC Whatever would be an option. Their transfer case shifts to N electronically.
If God's Your Co-Pilot Move Over, jd
2003 Jayco Escapade 31A on 2002 Ford E450 V10 4R100 218" WB