Hilux Surf 4WD Not Engaging (another one!)

[MSJW]

Hi guys

I have an automatic 1992 2.4l Hilux Surf that I'm getting back on the road after years of sitting dormant. 

The only remaining item to sort out is the 4wd system. Basically whenever I click on the button on the gear stick and shift into 4WD there's a clicking sound from behind the radio/ dash and 4WD does not engage. I'm trying this on a gravel road and only the front wheels turn. I've also checked the two fuses under the steering wheel which some say could be related to this issue but both look fine  

The 4WD light does not appear on the dash as it used to. I did undo one of the connectors to the transfer case actuator and when trying to engage 4wd there was no sound from the system trying to engage (as you'd expect). Once the connector was plugged back in I could feel with my hand some movement in the transfer case whenever we attempted to engage 4WD but still no lights on the dash. 

I'm thinking the 4WD button is working OK as there is a signal being sent to the transfer case when trying to engage all wheels. If the button itself or a relay was broken then I wouldn't expect to feel the transfer case trying to engage. 

My next steps are to take apart the transfer case and check for water / clean accordingly. Has anyone else had this sort of problem and cured it simply by taking the transfer case apart and cleaning inside? 

Thanks 

Mike 

 

[Niccry]

On 7/29/2017 at 2:31 PM, MSJW said:

Hi guys

I have an automatic 1992 2.4l Hilux Surf that I'm getting back on the road after years of sitting dormant. 

The only remaining item to sort out is the 4wd system. Basically whenever I click on the button on the gear stick and shift into 4WD there's a clicking sound from behind the radio/ dash and 4WD does not engage. I'm trying this on a gravel road and only the front wheels turn. I've also checked the two fuses under the steering wheel which some say could be related to this issue but both look fine  

The 4WD light does not appear on the dash as it used to. I did undo one of the connectors to the transfer case actuator and when trying to engage 4wd there was no sound from the system trying to engage (as you'd expect). Once the connector was plugged back in I could feel with my hand some movement in the transfer case whenever we attempted to engage 4WD but still no lights on the dash. 

I'm thinking the 4WD button is working OK as there is a signal being sent to the transfer case when trying to engage all wheels. If the button itself or a relay was broken then I wouldn't expect to feel the transfer case trying to engage. 

My next steps are to take apart the transfer case and check for water / clean accordingly. Has anyone else had this sort of problem and cured it simply by taking the transfer case apart and cleaning inside? 

Thanks 

Mike 

 

Hello Mike, did you ever figure out what the problem was. I am currently experiencing the same thing.

[Darrie]

It's a sort of two part system.... 4wd lever changes the drive ratio (high to low), but up front there is the ADD (Automatic Diff Disconnect) system that is vacuum controlled and engages the front differential to one of the front axle shafts (the other drive axle is permanent connected) by a shift fork. The 4wd light on dash comes on when the shaft is engaged, a sensor (white plug) on the front differential tells dash light it's connected. You can connect the shaft in high range via the button, in low range system automatically engages & the 4wd light comes on. 9 times out of 10 its a hose issue as the actuator selection is vacuum driven, and these little rubber lines perish over time.

Start simple testing by parking on the grass or a loose surface, select low range. This bypasses the 4wd button, then nudge forward then backwards. If the 4wd light doesn't come on then its not a 4wd switch issue. Leave the truck running out of gear in park but in low range. Have a blanket ready to lay on !  Going into the front diff are two vacuum actuator lines from the engine bay, remove one at a time, at least one should have a vacuum on it when you place your finger over the hose and your finger will stick to the hose. If no suction on either,  time to test the Vacuum Switch Valves (VSV's) located in engine bay behind the fuse box on the drivers side.

Motor running & still in low range ( but park) going into the top of the VSV's there is a single vacuum line (that splits into 2) to the engine vacuum source which with engine running & in 4wd sends vacuum to the VSV system. Test the top line to see that vacuum pressure is there when you place your finger over the hose.. if not that rubber line may be split & needs replacing. If good vacuum pressure then reattach & then test there is vacuum pressure on one of the the ports below (these two lower vacuum line hoses go to the front of the differential to engage & disengage the shift fork). Careful to remove one hose at a time so you don't reconnect hoses up wrong. As one hose is off suck on it and place your tongue over the hose. It should hold pressure, that tells you that lines going from the engine bay to the front diff are good...... do that on the other line as well, and if both hold a vacuum and your tongue stays stuck to the hose then lines are fine & not cactus. 

If everything is working Ok vacuum wise then its possibly an issue with the fork actuator in the diff (not usually the issue). But all these things are simple tests you can do to eliminate a failed hose that when split (or disconnected) cant place pressure on the front ADD actuator.

To help understand the system see the attached image.

Cheers

Darrie

[divejunkie]

On 2/6/2021 at 1:32 PM, Darrie said:

It's a sort of two part system.... 4wd lever changes the drive ratio (high to low), but up front there is the ADD (Automatic Diff Disconnect) system that is vacuum controlled and engages the front differential to one of the front axle shafts (the other drive axle is permanent connected) by a shift fork. The 4wd light on dash comes on when the shaft is engaged, a sensor (white plug) on the front differential tells dash light it's connected. You can connect the shaft in high range via the button, in low range system automatically engages & the 4wd light comes on. 9 times out of 10 its a hose issue as the actuator selection is vacuum driven, and these little rubber lines perish over time.

Start simple testing by parking on the grass or a loose surface, select low range. This bypasses the 4wd button, then nudge forward then backwards. If the 4wd light doesn't come on then its not a 4wd switch issue. Leave the truck running out of gear in park but in low range. Have a blanket ready to lay on !  Going into the front diff are two vacuum actuator lines from the engine bay, remove one at a time, at least one should have a vacuum on it when you place your finger over the hose and your finger will stick to the hose. If no suction on either,  time to test the Vacuum Switch Valves (VSV's) located in engine bay behind the fuse box on the drivers side.

Motor running & still in low range ( but park) going into the top of the VSV's there is a single vacuum line (that splits into 2) to the engine vacuum source which with engine running & in 4wd sends vacuum to the VSV system. Test the top line to see that vacuum pressure is there when you place your finger over the hose.. if not that rubber line may be split & needs replacing. If good vacuum pressure then reattach & then test there is vacuum pressure on one of the the ports below (these two lower vacuum line hoses go to the front of the differential to engage & disengage the shift fork). Careful to remove one hose at a time so you don't reconnect hoses up wrong. As one hose is off suck on it and place your tongue over the hose. It should hold pressure, that tells you that lines going from the engine bay to the front diff are good...... do that on the other line as well, and if both hold a vacuum and your tongue stays stuck to the hose then lines are fine & not cactus. 

If everything is working Ok vacuum wise then its possibly an issue with the fork actuator in the diff (not usually the issue). But all these things are simple tests you can do to eliminate a failed hose that when split (or disconnected) cant place pressure on the front ADD actuator.

To help understand the system see the attached image.

Cheers

Darrie

Hi Darrie,

I have a gen 2, with the 3lt diesel. I have been having a problem with the 4wd system, it changes into 4wd via the shifted lever ( so from hi to low) with a problem, but when I want to put it into 4wd hi by pushing the butten nothing happens. What do you think is the problem? and how to fixs?