chromatest

This is a story about a 2000 Tacoma SR5, V6, 4WD Manual 5 speed with J-Stick manual transfer case...

So I had some work done on my truck and never got around to testing out the 4WD. Then one day after doing a test-tow with a trailer, I noticed that the 4WD J-stick was in 4-Hi!!! YIKES!

I put it in 2-Hi and decided that I'd test it out later.

I tested it last night. In the dark and cold, but luckily in my drive way. I put the transfer case in 4-Hi and stomped on the gas to see which tires would spin. It *seemed like* the rear tires and the front driver's spun. After testing it a bit more, a HORRIBLE grinding noise started coming out of the front end, only when the truck was moving. It happened in 4-Hi and 2-Hi.

Disgusted, I parked it for the night.

Today, I did a bunch of research, pulled out the FSM, did more research....

Fairly quickly, I found that the horrible grinding noise was a pebble that got lodged between the disc pad and the brake shroud. phewwww...

After much messing around, I finally found that the 4WD transfer switch wasn't working.

Here's how I found it, and here's how I fixed it:

After trying a few things, I realized that I needed better information. So, I jacked up all four wheels (use jack stands and make sure it's on a solid level surface!) and gingerly put the truck in gear. Back wheels spun, no front wheels. I put it in 4-Hi and checked again. Back spun, no front. I carefully hopped out (you should have a friend help you) and looked under the truck and saw that both drive-shafts were spinning at about the same speed (pretty fast). That let me know that the transfer case was working properly, and that the problem was either in the front diff, or in the system controlling it.

Using a common multimeter with "beeping" continuity mode (test it by holding your two probes together and hearing the beep), I tested both switches on the transfer case. You can test these switches with the truck off and the keys out. They are simply contact switches. When the switch is engaged, you either have continuity (a beep) which allows electricity to flow through it, or you have an open (no beep) with no electric flow.

There is room for two switches on the driver's side, but only one switch. The other spot has a plug in it, but would have a switch if it were an automatic transmission (afaik). I think that one switch on the driver's side is to let the vehicle know that it is in 4-LO. There is one switch on the passenger side. It's kind of a bitch to get to, unless you have a decent body lift. Both switches have wires coming out of them, so you can unplug them and pull the wires down to get your meter into.

Both switches appeared to be bad, but I realized that I never put the truck into 4-LO, so maybe that switch is okay.

The 4-HI switch appeared bad, so I decided to test the system without the switch. I took a short piece of wire with the insulation stripped back a bit on each end. I folded it into a 'U' shape and pressed it into the connector that the switch would plug into (not into the switch itself). With the ignition on (truck not running), I could hear a relay activating. Pulling the jumper out, I heard the relay release. I tried it a few times, verifying that each time it was inserted, I heard the relay engage.

I left the jumper in place.

Then, with the truck still on blocks, I carefully entered the truck and started the engine. Putting it into gear now gave me all four wheels turning! To easily verify this with one person, I put some sticks on top of the front tires (you can probably lean out and see the driver's side tire). I'd put it in gear, let it go for a second and then put it back in neutral. Hopping out, I saw that the sticks were all on the ground. Again, if you had a buddy, they could simply tell you that the tires are spinning or not.

So, I took the jumper out, and removed the switch. It was a bit of a bitch getting a wrench in there. I ended up using vise-grips, since the switch was bad anyway. I took the switch inside and worked it a bunch. Still no continuity when the switch was pushed in. I then put it in the vise with the roller ball up and while pressing the ball all the way in, I sprayed it with a liberal amount of electric motor cleaner. I worked the switch a bunch, then flipped it over and kept pressing the ball until it was mostly dry. I then repeated the process.

Then, I checked for continuity, and the switched worked perfectly! I got continuity (beep!) about half-way in and the beep remained on while pushing the switch all the way down.

So, I reinstalled the switch (it's about a 1-1/16" drive). I used an old 1" box wrench that was bent and fit on well enough. I cranked it in, and plugged the switch into the harness. The ignition was still on (engine off), so as soon as I plugged it in, I heard the 4WD engage.

I put the wheels back on the ground and drove it around the back yard both in 4-HI and 4-LO. Everything worked fine.

The switch probably will need to be replaced for real, but for now, it's okay.

Something that I realized that could come in handy on the trail:
If your switch tests bad, (you *do* bring a cheap multi-meter with you, right?) you can easily snip the wires just before the switch (make sure which side of the wire-harness plug you are on!!!!!!), strip them back and twist them together (and throw some tape on it). That will lock your 4WD on. Just remember to crawl under and untwist and insulate the wires before getting on the highway.

Good luck!

TheDurk

If the vacuum front diff on a J-shift system is not engaging due to a bad switch, the quick and easy work field work-around is just to swap the two hoses coming up from the diff to the VSVs on the fenderwall. That will force the front diff to engage. A lot easier than messing with those switch wires. Just remember to swap them back when you go back to 2wd.

That's also how you test to figure out if the issue is in the vacuum half or the electric half of the system.

chromatest

Great point Durk! That one's obvious enough, but I totally didn't think of it. On my truck the vacuum relays (switches?) are color-coded. One hose has a blue marking on it, just before it connects to the blue relay. I assume that the hose connecting to the red relay has a red marking, but I didn't check. Swap the red hose with the blue hose (on one end only of course) and you've just swapped the vacuum that is "always on" which disengages the diff (making it 2WD) into the hose that engages the diff (making it 4WD).

Unless. of course, something is broken in the diff or the hoses are cut open or plugged, or the vacuum relays are broken.

TheDurk

...in which case jumping the switch won't do anything, either, of course.