I had this problem last winter and thought that maybe it was just the cold that was causing 4H not to disengaging properly when pushing the 4H button. However the problems seems to still be there. I press the button and the 4H engages no problem. I press is to disengage it and the light stays on. After repeated pressing of the button the 4WD light finally turns off. What could be causing this? If I do happen to get stuck in 4WD, can I simply unlock one of the hubs to avoid any kind of binding while driving on paved roads?
4H Not Disengaging Properly on BJ74
- Thread starter Canuck
- Start date
This site may earn a commission from merchant affiliate
links, including eBay, Amazon, Skimlinks, and others.
Follow the vac hoses from the solenoid,they are on the RH side on the firewall ,above the brake booster. One pulls it into 4H and the other pulls it out.
It sounds as if one has a leak or is loose at the junction.
To prove its a hose ,swap one over and the problem should be reversed eg it wont go into 4H easily.
Swapping hoses is the way you get home when it gets stuck in 4H out on the trail
If neither hose will work you can try getting vac from somewhere else.
You could also remove the diaphagm and shift it by sliding the shaft one way or another.
Maybe obvious, but: Do you make sure there is no strain on the drivetrain?
When disengaging and the light doesn't go "OFF" drive a few meters backwards and forward.
Especially when you are in even a slight turn the gears tend to bind because of the diffence in distance covered by the front and rear wheels.
Moving in opposite direction from last helps to free the gears.
So, if you have moving forward, move a few meters backwards after pressing the button. Have you moving backwards, move forward.
When disengaging and the light doesn't go "OFF" drive a few meters backwards and forward.
Especially when you are in even a slight turn the gears tend to bind because of the diffence in distance covered by the front and rear wheels.
Moving in opposite direction from last helps to free the gears.
So, if you have moving forward, move a few meters backwards after pressing the button. Have you moving backwards, move forward.
Yes! that is a good solution. But make sure you only disengage ONE of the two hubs as long as it is in '4WD'.
- Thread starter
- #5
Is the VSV located in the spot where Rosco described? On the EPC where would I find the VSV?
Yeah I try to reverse for a few meters and the light would still stay on.
Yep Rosco is right, it's at the RH-side, except you, having LH-steer rig will not have the booster in that location.
If you look in your engine-compartment near the firewall at the passengerside you will see the solenoid. It's a contraption with two black covers, about 3 cm diameter. It has some electric wires but also has 3 hoses connected to it.
One going to the vacuumsystem, two leading to the VSV.
Check these two.
The VSV is at the front of the transfer, alongside the gearbox.
You find it in the EPC in the powertrain section, fig 36-12
It a very simple piece with a membrane and a triangulare lever.
See pics: The first one view from below, the second one looking from the front to the rear ( you can see the front output of the X-fer, the third showing a part of the inners.
Last edited:
actually that picture is not the VSV...the VSV is the valve at the firewall.
that picture is of the Diaphragm cylinder and transfer vacuum actuator...
Oh man....that english language
!!:whoops:You're right.
Sorry, about the mistake.
Should have written 'the actuator' instead of 'VSV'
- Thread starter
- #12
Finally got around to taking some pics to confirm what part I'm after. I took these 2 pics, which one would it be?
I should also probably mention that the auto idle up that is supposed to happen when I turn the AC on doesn't work either. Is that linked to one of the items in the pics?
I should also probably mention that the auto idle up that is supposed to happen when I turn the AC on doesn't work either. Is that linked to one of the items in the pics?
- Joined
- Sep 28, 2002
- Threads
- 558
- Messages
- 8,123
- Location
- Kamloops, BC Canada
- Website
- www.shopraddcruisers.ca
Top pic
Finally got around to taking some pics to confirm what part I'm after. I took these 2 pics, which one would it be?
I should also probably mention that the auto idle up that is supposed to happen when I turn the AC on doesn't work either. Is that linked to one of the items in the pics?
- Joined
- Sep 28, 2002
- Threads
- 558
- Messages
- 8,123
- Location
- Kamloops, BC Canada
- Website
- www.shopraddcruisers.ca
The vacume is in the open position with the 4W High on, the actuator on the transmission if memeorey serves me pulls into gear. The actuator is spring loaded and when vacume is off it allows the lever to pull the 4wHigh gear out.
Could be a bit gummed up, maybe take it apart and make sure everything is moving smoothly.
Also to mention, when switching to 2wd, are you letting off the throttle and taking the pressure off the driveline?
Rob
Could be a bit gummed up, maybe take it apart and make sure everything is moving smoothly.
Also to mention, when switching to 2wd, are you letting off the throttle and taking the pressure off the driveline?
Rob
Check your plumbing as mentioned, as there may be an issue with a hose. The firewall ones are your 4wd (one to engage and one to disengage) and the one by the fuel sedimenter is your AC idleup.
The vacum works both ways...moving the arm in and out of 4wd. Whichever VSV is gone...no movey that way.
rosco's idea at the beginning to isolate and confirm fault is good.
hth's
gb
The vacum works both ways...moving the arm in and out of 4wd. Whichever VSV is gone...no movey that way.
rosco's idea at the beginning to isolate and confirm fault is good.
hth's
gb
- Joined
- Sep 28, 2002
- Threads
- 558
- Messages
- 8,123
- Location
- Kamloops, BC Canada
- Website
- www.shopraddcruisers.ca
Sure about this, thought the was a spring, which pulls the four wheel drive mechanism out of 4wd high, and both vacume hoses are used to pull the lever into four wheel drive high??
The vacum works both ways...moving the arm in and out of 4wd. Whichever VSV is gone...no movey that way.
The vacum works both ways...moving the arm in and out of 4wd. Whichever VSV is gone...no movey that way.
Hi Rob
Not high tech, but if you have a vacum t-case on the shelf apply vacum to one hose and it stays where it shifts when you take the vacum away. Apply vacum to the other hose, and it moves the opposite way.
hth's
gb
Not high tech, but if you have a vacum t-case on the shelf apply vacum to one hose and it stays where it shifts when you take the vacum away. Apply vacum to the other hose, and it moves the opposite way.
hth's
gb
- Joined
- Sep 28, 2002
- Threads
- 558
- Messages
- 8,123
- Location
- Kamloops, BC Canada
- Website
- www.shopraddcruisers.ca
- Thread starter
- #19
So this problem reared its head today again. The truck would engage 4H no problem but would not disengage. I swapped the two hoses that are facing the camera in the picture below and it disengaged. This would confirm that it is the VSV that is causing the problems correct?
Yes ,assuming the hose isnt leaking and the VSV is getting power. Could it be the cold? Maybe condensation frozen in the hoses?