4WD Issues

Ok, so my family has had a 2000 Tundra for about 14-15 years now. I’ve been driving it as my daily(mileage sucks haha), and my dad had said that the 4WD doesn’t work. Someone else I’ve talked to has said that most of the time, it has to do with the electronics.

My dad believes it to be the Transfer Case. He hasn’t really looked at it, but he said that it isn’t moving like it should be and doesn’t work.

How does one figure out what the issue is without spending a bunch of money to replace everything? I’ve looked at the repair manual, but it wasn’t super helpful. I still need to look at the truck myself, so it could be. How do I figure this all out?

 

Welcome to the forum from TX!

Any leaks? Noises? Lights on the dash? Codes?

 

Mostly has to do with the electromechanical actuator getting corroded and stuck. You can check out the electrical and see if everything is getting voltage when and where it should why someone else moves the selector. First check out all fuses and relays, then move forward from there because that would be easier than anything else. Wire diagram is here on the forum under garage heading and electrical subheading. The 4wd system needs regular monthly exercise or it will get locked up. What ever you figure out, post it up here for the next person with the problem. Good luck!

 

Not that I know of. The only “leaks” I ever get are from the coolant and AC, but that’s normal from condensation.

 

Thank you! I’ll check all of that. First I have to figure it out haha. I’m still somewhat new to all of this and my dad’s been too busy flying to take care of stuff sometimes, so I’m stuck doing it.

 

As mentioned, every month or so you’ll need to get used to exercising 4wd once you get problem figured out.

Given it appears it might not have been used in awhile, it might be as simple as bopping on the Transfer case with a hammer as someone attempts to select 4wd. As of now, what indications are you having….any blinking light when pushing button,hearing a clunking noise like something is trying to work ?

 

Honestly, I’d have to check. The last time I tried, there wasn’t any sort of blinking, but I don’t know if I tried moving when it was on. I’ll check that today. Definitely no noise I’ve heard, either.

 

Sorry, been a little busy. It does blink when I push the button, but I still haven’t tried moving when it’s on. I have a little bit of time in the morning tomorrow, so I’ll try moving when it’s on. Or try turning it on when moving. Will give update when done.

 

I suggest starting a thread in the regular 1st gen section instead of the build section. Probably get more traffic that way.
https://www.tundras.com/forums/1st-gen-tundras-2000-2006.2/

 

Also, in the “stickied” posts linked permanently at the top of the First Gen section, one has all the manuals. Make sure to read the section on 4WD operation just to see what order to push the buttons to engage, what gear you have to be in to make it work, etc.

Surprisingly it’s not intuitive! You definitely don’t just start mashing buttons.

Welcome from Texas.

 

Dunno how much you know about 4WD and some terms I'm hearing suggest you may be younger, so I’ll avoid making assumptions about your level of knowledge, apologies in advance if some of this seems “beneath” you, it’s purely for better-safe-than-sorry purposes.

4WD has 4HI and 4LO modes. To be overly-generic 4HI is what most use at normal speeds on wet/loose/slippery stuff. 4LO is what most use while crawling.

Our Tundras don't have all-time 4WD, i.e. while 4HI or 4LO is engaged, never try to turn the wheels on dry pavement or sharply on any pavement, esp. at low speeds. (Note: If you're a Sequoia reader, ignore that statement, you have all-time/AWD, Torsen diff)

Unlike 4HI, there's a special process to shift into 4LO. First you need to be in 4HI with the button/light solid, not flashing. Then shift to N. Then tap 4LO, IIRC.

Toyota requires, per the manual and as @BubbaW eluded, engaging the 4WD at least once per month, for 10-12 miles of use, to keep things clean and freely engaging.

My guess: Your folks bought this truck, didn't RTFM, and rarely engaged the 4WD. If you can ask them if that's true, it'll probably help greatly w/diagnostics.

If you find it *is* true, the fix is potentially really easy and free, something is probably frozen. We just need to free up whatever's stuck or corroded from non-use.
Before you start, some basic info you should know, courtesy of @FiatRunner who has been thru the ringer on this.

There are some basic things to check which others have reported to fix stuff, a checklist of sorts to follow:

1. CHECK/CHANGE YOUR FLUIDS. When was the last time you changed your fluids? Remember, always remove the fill plug 1st to make sure you can refill after draining. Watch closely when you initially open the drain plug to look for water. If your rear end is equipped with LSD, it should have a sticker to indicate this just left of the fill plug; it's not recommended to use synthetic fluids with LSD rear-ends in the 1st Gen Tundra, they're picky on fluid. Lucas 80w90 or Motul 90w is proven to work for LSD rear without chatter and no additive needed, Mobil1 synthetic caused chatter in my LSD rear.
2. Verify the 4WD fuse in the dash fuse box is good and wiring under the truck is intact, at all actuators, and not burnt (shouldn't be, but ... baby steps, check the obvious stuff first)
3. Check your wiring to the actuators just to ensure it's not loose or burnt up, as many members with same issue have found wiring to one or more 4WD component melted!
4. Watch the video at the end of my reply here; see the rubber vent tube on the actuators? Confirm yours isn’t missing, cracked, broken, not on its nipples, i.e. allowing outside elements inside the actuator itself. You’ll also want to check the cap for the corrosion that guy is showing in the video.
5. Put the truck in Park on a straight path at least 100-200yds long, with the wheels straight
6. Shift into D, let off the brake to start rolling, don't give it any gas, tap 4HI button.
7. Observe any flashes/beeps you hear; if none, and the light keeps flashing, brake until stopped.
8. Shift into reverse, roll 2-3ft back, brake to stop, repeat 3-4 times.
9. Repeat steps 3-5 a couple more times.
10. Some found tapping the actuator and transfer case with a mallet or hammer and then repeating steps 2-6 have helped. May require a 2nd person, be careful.
11. Some found tapping light taps on the actuator while trying to shift does the trick. May require a 2nd person, be careful.
12. Some found simply lifting popping the actuator cover off and checking/cleaning the contacts frees it up.
13. A couple of people, in cases where 4WD actually was engaged semi-regularly, have found the 4WD ECU is just ... toast. It happens. Doubt it's your case though.

If the term "actuator" etc. isn't clear, I would tell you to watch this video to help with next steps with at least one of the actuators.

You'll see where the actuator is at the 1m30s mark, the black plastic circular cover is the cap in question. He briefly explains what you can do with the actuator once the cover is off to manually test shifting into 4WD using a power probe (check the 0m40s mark). He also draws out how the actuator works starting around 2m00s. He shows how to take the actuator cap off at 12m25s and addresses the vacuum line, which some have found off/split, one source for outside elements to allow corrosion.

At the 13m05 mark, you'll quickly see how/why this actuator can get gummed up if not used, or if the vent hose is lost/unhooked, just look at how gummed up it is in there. Skip to the 13m32s mark and look at the to ther side of the cap. Try cleaning the contacts (see 15m02s mark for cleaning and what to look for). Use something that won't cause later corrosion, then liberally apply some di-electric grease on all the contacts for protection before reassembly and test. HEED THE WARNING AT 14m20s!!

https://www.youtube.com/watch?v=TmuEVv1neVQ​

 

I've mentioned this here before, and I'm not sure how much good this will do for you, but press the 4WD button while looking at the voltage gauge. If the 4WD computer and wires are intact and functioning properly, you should be able to see the voltage drop for a second or two while the computer sends power to the actuator, and puts load on the alternator.

This can be a quick and easy way to tell if the actuator motor is receiving power, or if power is being sent somewhere.

 

Thank you all. I’ll check those things today. I don’t have a second person at home with me currently, so I can only do so much. My family got it for free from one of my dad’s bosses about 14-16 years ago. I don’t know how often my dad used it(I was young haha, being 18 right now), but there were a few years where it was in the driveway. I remember my dad had to take a BB gun to get some squirrels out and he fixed a bunch of stuff they were eating up. It was enough to get it on a trailer for moving, and it sat for about a year or two before my dad finally got it fully working(I guess minus the 4WD). I know that we have a manual for the Tundra and Sequoia models, and have looked at it for stuff when working on the truck. Anyways, I’ll take a look at it now.

 

Yup, on the V8 it's really common for rodents to get up under the intake and chew the starter wires and knock sensor wires up. Likewise, it's common for them to nest on top of the fuel tank and chew that wiring up. Always a good idea to check the air filter box to look for shredded stuff there also.

Anyway, if this is your first adventure into "1st Gen Tundra ville", before you read another reply, head over to the thread Bubba linked you up with and read it in full, and pay close attention to the early links for service manuals, etc: https://www.tundras.com/threads/so-you-wanna-buy-just-bought-a-1st-gen-tundra-eh.115928/

It'll give you nearly all the warnings you need to hear, and even links back to this exact thread for 4WD diagnostics

Keep updating over here, and we'll keep answering. Lots of really good quality folks in this forum who can help guide you on your way. These trucks were pretty damn incredible value, and are becoming more and more sought after as they continue being seen hitting 500k miles, 600k miles, 700k miles or more on the original engine and transmission. They have their faults like any other vehicle, but ... great trucks if you care for 'em.

 

So the fuse is good, but I don’t know where that wiring is. I have work in an hour so I’m trying to do what I can right now.

 

Also, I pressed the button again and I didn’t see the voltage gauge go down or up.

 

This isn't a definitive test. I was curious and went out to my '06 and did the same. I didn't see a rise or drop.

Not saying it doesn't work, maybe it does make a voltage drop if you have a load and a 100A alternator versus my 130A, but it didn't do anything on mine.

 

Right. Maybe.

 

So, I was doing steps 2-6 and tried banging on what I thought was the transfer case and repeating 2-6. I heard and felt it try to do something, but the 4HI kept blinking and on the dash ‘4HI’ was blinking as well. I have to get to work now, but when I get some time, I’ll watch the video and try some of the other steps. I couldn’t spot the ECU or the actuator, even after looking at the manual.

 

Video will help you find the actuator.

 

Understood.

 

I’m going to change the front differential gear oil, cause someone said that would be wise and could be part of the problem. My dad said he’s never changed it. Then I’ll check the continuity of some things to make sure everything is getting power. Then I’ll check the actuator if nothing else works. I checked the actuator assembly and all was fine. I’ll have to get a replacement vacuum hose, but I don’t know what the proper size is supposed to be.

 

The actuator is not vacuum operated I believe what you are seeing is a vent hose. If that's disconnected it's likely there was/is water in it.

While changing the front diff fluid isn't a bad idea I find it unlikely that it's causing your problem. It's almost always an actuator issue. Either corroded or "out of time" with the other actuator.

 

Aye, the hose was connected still, but it’s corroding. It needs to be replaced soon, I just don’t know what the right size is for it.

Yeah. Someone I know who is a mechanic suggested to do that first, in case that was clogged up(hasn’t been changed for as long as we’ve had it). I’ll check the actuator when I can find it.

 

Diff fluid almost assuredly isn't the problem and doubt changing will fix the problem. Mine wasn't changed in its whole 70k+ miles, and it looked new out of the bottle, while my front/rear diffs showed ample signs of use.

The breather/vent hose tends to crack. Someone else was showing us that recently. If it cracks, air gets in, contacts oxidize. I wouldn't be the least bit surprised to see taking off the actuator cover (instructions in that video I posted) exposes corrosion on the contacts... which you should be able to verify and clean up with it still installed.

 

I’ll still change it when I can, then. I’m having a hard time with the drain plug anyways.

I already checked the contacts. They were fine. The vent hose isn’t bad enough, but it’ll get there. I think I found the actuator(or the ADD actuator), but I don’t know what to do with it.

 

If you don't know this already, always pull the top fill plug first, then the bottom. Mine were pretty easy to pop off, but then again, southern truck, virtually no corrosion.

IIRC, it was a 24mm for the rear diff and tc on my truck. I used a standard ratchet, no breaker bar. Front diff is another story. Breaker bar mandatory. Not only because of the tight spaces, but different plug type (10mm allen, with a torx below in the base in case you strip it) with a large flat top which I find tends to freeze.

 

+1 everything Shifty said. I doubt your diff or TC fluid is the culprit. My money is on the actuator or the wiring. There are some good videos on this site and YT showing how to fix. Be aware the actuator is pricey from Toyota. Since you insist on changing fluids buy some new crush washers and plugs. The Lexus plug is a better design as it doesn’t use an Allen wrench. Be sure to use the correct fluid viscosity and type depending if you have a LSD. Post photos and keep asking questions.