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!
Hey, My controller just crapped out and I'm getting ready to do this fix for the front and rear. If I use rubber vacuum lines, will they slide into those connectors on the switch and stay connected in the same way that the hard blue line connects? What size vacuum line do you need, is it 1/4 ID? Also, is this the correct switch? Thanks, your tutorial is very helpful, just wanted to confirm a few details.
Nevermind on the switch, it's not this one, it's a 4R210-08, I found it near the beginning of the youtube video.
So when I did mine on the front I used only the blue poly lines and they slide over the diaphragm perfectly and I've had no problems with 4x4 since the snow and ice hit recently. The rubber hoses are not going to fit into those john guest fittings as the OD is too large. The ID is 1/4" and I would recommend buying the exact stuff you see listed in the video description. Hope this helps! Here's the video link for convenience
I completed this fix today, pretty straight forward. Hardest part was getting to the controller to unplug the wire harness. I used the plastic tubing and it fit tightly over the small pipes on the diaphram just as coolscott said. Here are some additional pics. IMG_1531 by jhud posted Dec 22, 2024 at 8:47 PM IMG_1532 by jhud posted Dec 22, 2024 at 8:47 PM View attachment 23727
I believe my axle won't disengage.Push the switch could not get light to go off, jiggled wires and now it does toggle and I can hear it clicking but tires will not spin freely. Does the vacuum engage or disengage axle?My selector does seam to operate between 2 wheel,4 wheel and 4 lo. My only test on that is front wheel skip during a 180 turn. Took off front disc pads and still have drag then tore down to bearing and it spun easily.With tire on I can only spun 1/2 turn.
That cannot be such an important comment to make. One letter off and the two are right next to each other on the keyboard. Don't comment if you have nothing useful to say, it just clutters up the thread. My understanding of the axle lock is that there is both a vacuum that pulls to engage the lock and a second line that pulls to disengage. I would do the basics like check all your connects are good and don't leak. square clean cuts on the lines and check for cracks or kinks. You could also try changing the differential oil in case that's part of the issue. Other thing is that your truck is 30 ish years old and things break, the mechanism seized and you either need to rebuild it or replace it. Neither is going to have many resources. Maybe try tapping the diff to u seize it? Might be S.O.L
Front Differential 1.7L hypoid API GL-5 75w-80(or 90) Found this on a different thread. I haven't taken the time to change it myself yet.
drained both axles and trans +gearbox(1 reservoir covers both). front axle(my biggest issue) had less than 1/2 liter, around 15 ozs, dirty,should be 1.7 liter. rear diff I got between 11 and 12 oz from FILL hole (do not understand , maybe 2" lift kit)and another 22ish from drain hole. total 34, just over a liter, should be 1.3 L. main drain on axle is offset a bit so I jack up passenger side and got maybe another oz, close enough for me.i guess I will lift front end to get to 1.3L fill.t&g reservoir was full of clean oil. hard to measure this much. about 85 oz that =2.5 L should be between 3.5 and 3.7,but my trans bell housing hole to check timing marks was missing a plug,thank you t_g_farrell, so I assume I was losing fluid on every drive.I have a rubber plug in it now and will keep an eye on it to make sure it is secure.clean oil in t&g reservoir but magnetic drain plug was lousy with dirt and metal, I consider previous oil change a good wash.waiting for new oils so I have not refilled yet, gl 4 for t&g. gl5 for axles.time to watch football so I know who the RAMS are going to WHOOP on!!
Hi. Loved your fix but I just wanted to take a moment and share my fix as well. If your Axle Lock is intermittent and you believe it's related to the 4WD Control Box there's another way to bypass the box that is MUCH easier than the vacuum fix. All of my vacuum lines and solenoids are working great so I think it's easier for me to unplug the controller box and then power the solenoids directly via a switch. On the rare occasion my controller box was working, I measured the voltage to the solenoids and with was a 12 volt constant which is why I was able to just connect power directly to the solenoids. Mine is a 1995 Suzuki Carry with a 4 speed manual with four wheel high and low. I just finished this process and everything works perfectly. I now have Axle Lock with the flip of a switch. I completely bypassed the 4WD Controller box that you cannot buy new anymore and the used ones, that are probably on their last legs, are $300.00 and up. I'm not paying $300.00 for a used electronic part that is 25 years older, or older. My method cost me, roughly, $10.00 for a new Cambridge Toggle Switch, Part #202187, with an LED Light and a few feet of wire and connectors. I found a 12 volt source with the key on and tied into that for my power to the switch. I then wired the power from the switch to both solenoids. I made sure the toggle switch has a safety cover over it so you can't mistakenly switch it on while your moving. I'm so glad to bypass that crappy 4WD controller as it seems all of them have failed, are failing, or are soon to fail. I just wanted to share this with everyone as this was MUCH easier to accomplish than the vacuum bypass. Hope this helps some of you!
Sorry, I just think your fix is still more complex than it needs to be in that you're still employing solenoids to activate/deactivate the vacuum to the actuator. It maintains a complexity (the solenoids) that isn't really necessary. I still prefer the simple on/off nature of the vacuum switch. But it's still a fix, and a worlds simpler solution than the one Suzuki's engineers designed. Nice work.
Thank you my friend. I do like the simplicity of a pure vacuum/Non Electronic fix for sure. I did it with a switch which works great and was much easier to do for the average layman. I do agree that vacuum is, without a doubt, a better more permanent fix. Thank you for your comments. It's always great to get other points of view. Keep on truckin!
I haven't been able to find details on a couple of items on this mod... What are people using for the vacuum source? Does it matter which port goes to which line? I'm assuming it does - but I can't seem to find details. Thx EDIT: I way over thought the difficulty of this. Hardest part was mounting the switches in a comfortable location!
