Like many, I've had problems with the Axle Lock engaging when first starting or while driving ('95 DD51T, 5spd, 4wd, no dif lock). I've given up on finding the non-obtanium control module, but found an excellent and simple solution on YouTube, courtesy of Mike Festiva ("Maintenance Guide for Suzuki...." 17:43 minute mark). It involves installing a two-way manual vacuum switch and running vacuum directly to the axle lock actuator atop the front differential: Pull up, the axles engage; push down, they disengage. No chasing wires or dealing with solid state electronics. Basically, the in-cab equivalent of locking the manual hubs on the older models. What do you think?
Okay, I've finished the Mike Festiva axle lock solution, and it works great. This fix will bypass the electronic 4wd module that tends to fail after 25+ years, providing a reliable way to engage the front hubs. Begin by removing the VSM and all its wiring and vacuum lines. When removing the wiring be sure to leave the status switch wiring intact (the wires with the white connector). 1. The new switch, a simple 3-way on/off vacuum switch sourced from Amazon, will be mounted on the center console. 2. Run one new vacuum line from the port between the brass vents on the new switch to a vacuum line on the engine. I used the original source of vacuum to the VSM. (Note: In the background, you can see the two vacuum lines running down from the new switch to the actuator atop the front differential.) 3. Run two other vacuum lines from the other ports on the switch down to the front axle lock actuator (on top of the differential). (Note: You will need to slide small rubber vacuum line leads onto the metal diaphragm tubes so you can connect the blue, harder urethane tubes onto them. I sourced the adaptor pieces at ACE Hardware. This won't be necessary if you use all rubber vacuum line.) 4. Once all the lines are connected, check to see if you need to reverse the two vacuum lines exiting the switch so the axles lock when you pull up on the switch. That's all there is to it. Many thanks to Mike Festiva for the original idea.
Hey man! Thanks for posting this. My 95 Carry axle lock doesn't engage (even though the light is always stuck on) so I was planning on implementing this. I couldn't figure out why Mike went with the 5 port switch instead of the 3 port switch you went with. Appreciate you providing step by step instructions with pictures! Not sure if you're still associated with Tucson but I lived out there for a few years and it holds a very special place in my heart.
Yeah, I've lived here for 20+ years now. The axle lock fix is still working great after three months now.
Awesome! I’ve yet to take the front diff apart yet but I have a feeling the fork that engages the axle lock exploded when the axle lock kicked on at full speed. Want to confirm first but I checked and G&R had a front diff available. I’m going to apply the fix to the new one for sure to prevent any mishaps.
I need your help here. Instead of a manual vacuum switch, what if I apply voltage by a switch to the vacuum solenoid? This will open or close it. The more important question is, how do these work as far as why is there two of them? Is one to engage the lock and the other to disengage the lock? In that case one gets voltage to engage AWD and one gets voltage to disengage AWD. Does your dash show the green 4wd light?
It seems that should work. My intent was to simplify the system by removing the electronic aspects of it (which I did successfully). The failure of the 4wd module in these trucks is common, and a replacement module is seemingly unavailable new, and expensive even if used (and I try to avoid using used parts in repairs if at all possible). The entire original system, in my opinion, is unnecessarily complex, and the simplest solution is usually the best one. The entire purpose of the system is to provide vacuum to the actuator to lock and unlock the front hubs. My solution provides vacuum to the actuator with a simple on/off switch, removing the complexity of the module and solenoids. My 4wd status light does still work because, as I mentioned in the first paragraph of my description, I was careful, when removing the now-extraneous wiring, to leave the status switch wiring intact. Hope that helps.
Note: Mike uses the same switch, just a difference in terms; he counts the two exhaust ports, making it 5 instead of 3. I count only the vacuum connection ports.
just found out my Carry(DD51T) doesn't have the 4WD computer at all, gotta love Facebook MP. i plan on trying out this solution you shared but i was curious if my 4wd switch will still work without the computer. i imagine the 4WD just engages at the transfer case, and the axel lock is required to actually transmit the power to the front wheels, but I'm no expert. I understand that the axel lock is just a diff lock for the front wheels, but i don't know how it interacts with the driveshaft. i dont have any high/low switch just 2wd to 4wd. thanks
My '95 Carry also doesn't have high/low 4wd. In lieu of that, it has the additional Extra Low gear ("EL" on the shift knob), which is only available when the 4wd is engaged. The 4wd module was just a complex way of doing what the manual vacuum switch does--provide vacuum to the actuator to lock the front hubs. The transmission of power to the front drive shaft is mechanically accomplished by the lever between the seats. The module (and the button on the lower right of the dash, labelled "Axle Lock") simply engaged the front hubs. (BTW, I disconnected and removed that button as well.) As I mentioned in my original description, you do want to leave the wiring for the 4wd status switch (the wires with the white connector) intact so that the green 4wd status light will still light up in the instrument cluster when 4wd is engaged. Hope that helps.
Thank you for the response! I installed the vacuum switch as described and it worked great, all i did was remove the solenoids and the 4WD light worked. (did discover i might have a transmission issue) 4wd drive worked properly and i have yet to test it out under load but thanks for sharing the idea!
