PVH stuck in 4wd

[Blake0000]

I have a 1999 ford ranger 4wd. It has the PVH (pulse vacuum hubs) system for locking the front hubs in 4wd. My hubs seems to be stuck locked in 4wd and I can’t find anything on how to fix it. When you switch it back to 2wd the transfer case disengages but the cv axles stay connected to the wheel hub assemblies. It wasn’t that big of a deal at first because I know in 2000 they switched to a live axle system where the cv axle and hub assembly were locked together all the time. Now though I’ve started noticing a constant scrap/squeal as my front driver wheel rotates and my gas mileage has went down. So I removed the tire and all brake components and checked the noise it was there while spinning the hub assembly but when I removed the PVH hubs and just the hub assembly was spinning without the cv axle connected the noise wouldn’t happen. Also because they are staying locked together my front drive shaft spins as the truck moves and around 60mph I hear a random pop sometimes. I’ve checked the vacuum lines and the solenoid I have 20 in hg of vacuum everywhere in the system in 4wd and 0 in hg in 2wd. So does anyone know if if I am correct on my diagnosis and if so does anyone know how to fix it without buying new parts.

 

[RonD]

Welcome to TRS

The propeller joint on the front drive shaft at the transfer case is failing, thats the popping noise, for sure

As for the PVH hubs, they were only used for 3 years(1998-2000) so not alot of parts or info available on them, most problems require replacing with AVM Manual hubs

PVH Guide here: https://therangerstation.com/tech_library/ford_ranger_pvh_hub_operation_and_troubleshooting.shtml
And here: https://therangerstation.com/tech_library/troubleshoot-fix_pvh_hubs.shtml
But reads like you have tested it already

MPG shouldn't be effected that much, .3MPG lower is expected with live axle
You may have a Hub issue, not the 4WD part, but they should unlock

AVM hub swap info here: https://therangerstation.com/tech_library/AVM_hub_swap.shtml

 

[Blake0000]

Thanks for the info. I was already thinking of the avm hubs if I couldn’t figure anything else out. I just can’t find anywhere to purchase them besides eBay. I’ll also look into the propeller joint I was just really hoping it hadn’t started to affect my transfer case

 

[RonD]

The propeller joint was a weak point(known issue) on all 1998 and up Rangers and Explorers, not a transfer case issue, just a design issue

Not unlike the PVH Hubs

 

[Blake0000]

Well I finally got the wheels back in 2wd. I took the PVHs apart and got the spring inside it to lock back into place where it wasn’t putting pressure on the ring that locked the splines together. It’s holding for now but i don’t know how long it will last. I did realize though from the links you sent that I need 6-7 hg of vacuum when I switch the truck back to 2wd and I was reading zero on my gauge so maybe my vacuum solenoid is bad after all. I’m going to re test everything tomorrow. Also is there any way to check the propeller joint besides check for leaking grease and the condition of the rubber around it? When I checked mine it was dry and the rubber showed no signs of deterioration.

 

[RonD]

No I don't think there are outward signs unless it fails completely

In 2WD, with hubs unlocked, you should be able to spin the front drive shaft and listen for the popping, it was generally heard on AWD or Live Axle at lower speeds

Look here: https://www.amazon.com/APDTY-Driveshaft-Mountaineer-1L2Z-4A376-AA-XL2Z-4A376-AA/dp/B00C8EA9DE

The ball bearings allow the drive shaft to change angles and they get loose, and cause the popping, the factory units are sealed so no way to add lube, but if there is popping then its probably too late in any case

 

[Blake0000]

Alright thanks that’ll be my next project figuring those out. Back to the hubs though if you don’t mind. I learned more than I thought I had found when going through your previous links. Today I had a buddy help me so I could watch the vacuum and time it. When switching to 4wd it held 20 in hg of vacuum for 60 seconds. Then when switching to 2wd it climbed to 15 in hg in about 6-7 seconds and dropped to zero. Could I be getting to much vacuum when switching to 2wd and it’s compressing that spring past the 2wd locking point in the hub. Ultimately letting the spring extend back out to its 4wd state. I done my testing from the vacuum solenoid out port by the way.