This route is currently signed as country road J1 from Highway 25 South of Hollister to 180 in Mendota, in Fresno County. It is proposed Route 180 in the Streets and Highways code. On old maps from the 1960s you will see 180 signed along this route, and further along 25 until US101 just south of Gilroy.
If 180 was finished it could take one of two routes. The current route of J1 is longer than Little Panoche Road, which takes a more direct course. Little Panoche Road is a dirt road from the tiny town of Panoche to Interstate 5. I actually tried to do it once, and that was a mistake. Not only is it dirt, it has streams several feet deep crossing the road bed.
The area between 25 and Interstate 5 has several tracts of BLM land, where you can go camping, target shooting, or sight seeing. Virtually no one will be on the BLM tracts of land, in fact, so deserted is this area that even on a holiday weekend you will see virtually no one out this way. The tracts of BLM land are off very rough dirt roads (the kind that can mess up the suspension in your car!) but also extremely scenic. If you want to explore these tracts of land, get maps and regulations from the Hollister office of the Bureau of Land Management. Not following the rules can wind you in trouble.
J1 leaves 25 as a wide fast route. It gets narrower and slower
(25 mph or so) as you enter the hills near Panoche Pass (2800' up or
Then it becomes one lane wide for a while going down the Pass. It has
bad curves and poorly banked sections that can throw your car airborne
if you're not careful. It straightens out in the Panoche Valley and
the hills near the Fresno County line. Near the Fresno County line it
over Shotgun Pass (1650' up). From there to Interstate 5 it is
40-45 MPH and two lanes wide. It passes near a reservoir a few miles
of Interstate 5. If you continue on to Mendota, you will rejoin the
route 180, go through Fresno on some new sections of freeway, and then
go into Kings Canyon National Park.
Now headed west. This set starts just west of I5.
Looking at several peaks that are located on BLM land. The set of
antennas is on top of Panoche Mountain (Elevation 2095')
is in an area where you can camp on BLM owned land.
Several miles west of I5. This is near Little Panoche Detention
You can see the back of the pointy shaped peak to the right from
Gilroy. This is looking up a dirt road that meets J1.