I've seen a lot of similar threads to my issue but every single one has mentioned something about their front axle not spinning, which isn't my case.

I've had my ranger for just about a year and it's always been super reliable and the 4x4 has worked beautifully. Recently, I decided to test my luck by heading up an off-road mountain, only for the 4x4 to go out half way up and leave me stuck in the snow.... embarrassing. Today i was able to get the truck lifted to confirm what my issue is with the 4x4 and I quickly found out that the front axle is indeed spinning on 4HI-4LO but the wheels were not. I've read that if that is the issue, it is a vacuum line problem. I checked both sides, and the line is intact to where it connects behind the wheel. I checked the fuse to the PVH solenoid and it's fine. I'd like to fix it the correct way, not by modifying the hubs if possible. If anyone can help, it would be greatly appreciated.

 

Welcome to the forum

First, locking front hubs, manual or automatic, work by having a splined drive axle and a splined hub
Picture here, not Ranger: https://i.ytimg.com/vi/F441XfFCPN0/hqdefault.jpg
You can see the splines on the outside of axle and inside of hub, and there is no connection between them of course, so 2WD

If I were to insert something like this between axle and hub: https://cdn.shopify.com/s/files/1/14...g?v=1625668826
Then they would be Locked together, 4WD
So the manual or automatic hubs slide that in between gear in and out to lock and unlock a front wheels hub, simple

PVH(pulse vacuum hubs) were used in 1998 to 2000 Ranger 4x4s
Its a pretty basic system with lots that can go wrong, lol
But it will work, just has to be repaired more often than manual hubs

This will be an odd question, but does the Vent select control work in the cab, i.e. can you change from defrost to panel and to floor?
The cab vents are vacuum controlled and use the Vacuum reservoir in engine bay....................and so does PVH
So if cab panel or floor vents can't be selected neither can PVH

When you select 4WD on the dash switch the GEM module(4x4 controller) activates Shift Motor to change transfer case to 4WD and also activates the PVH Solenoid, 12volt valve

The PVH solenoid is on passenger side frame rail about mid-engine, has a 2 wire connector and 2 vacuum hoses
1 vacuum hose goes to the Vacuum reservoirs hose, vacuum source
Other vacuum line runs to a splitter on the front axle and then one vacuum line to each wheel
Diagram here: https://www.justanswer.com/uploads/m...5_030200_1.png

For the system to work all hoses need to be air tight, of course
You can use a 9v battery to test solenoid, no polarity, should "click" when it has + and -, or you can pull it out and test it
Also good to try and blow thru it, shouldn't pass air until its activated

When PVH solenoid opens vacuum is applied to both front hubs which Sucks in the in between gear(as seen above) to engage axle and hub for 4WD
This means the hub also has to be air tight, and this is one of the failure points, there is an inner seal that will leak at some point
You can remove front hubs vacuum line from the splitter or use you own vacuum line and suck on the hose to see if that hub holds vacuum
Also test for vacuum on hub hoses with engine running and 4WD selected

The front differential is an OPEN type, which means if either hub doesn't lock then no 4WD, BOTH hubs need to lock or no 4WD

Some good pictures here of PVH hubs: https://www.therangerstation.com/tec...y-replacement/

A vacuum gauge and hand pump is handy to have for PVH diagnosis