4x4 stuck causing drastic MPG loss

It's not unheard for the 4WD actuator in the transfer case on electronic shift Toyotas to hang up in a partially engaged position. Depending on the reason it may be the sensors and might not blink the 4WD dash indicator. I'd still also check the A.D.D. as well, but there's just so many pieces to switch between 2WD, 4WD and low range that have to fall into place that it's rife with possible issues.

Google it, weird things happen with 4Runners, Tundras, even Sequoias. Usually it won't go into or out of 4WD or the dash lights are blinking. But who knows, there's probably other ways for the system to go into the weeds.

 

I would think driving thru water with the A.D.D. actuator motors submerged is a problem in the making . I also would prefer manual shifting of the trans case and hubs. Even the auto hubs on my 98 Dodge were a pain because sometimes I had to backup 10 to 50 feet for them to engage or disengage etc. So I had to know I needed 4x4 before I launched my boat. (spinning one rear tire on a boat launch was too late as you cannot back up any further!)

 

An experienced driver will notice he is in 4X4. Someone less experienced may well not. Right after graduating from HS I bought a used 1975 Jeep J-10 4X4 truck. They came with "full time 4X4" at the time. Basically it operated as an AWD vehicle most of the time, but had a switch that worked off vacuum hoses to lock the transfer case and make it true 4X4.

At some point prior to me buying it the vacuum lines were reversed and it was locked when in the unlocked position. I was smart enough to know not to lock it on pavement, but not experienced enough to notice the problem. The drive chain in the transfer case stretched and began slipping on the cogs. I had to have it replaced twice before figuring out the problem. Had it not been full time 4X4 I'd have figured it out sooner. When off roading I locked the transfer case. It was still operating in AWD and I never got it stuck. I'd have known something was wrong had the front wheels not been pulling.

I figured it out one day while pulling into a parking lot at school. Later that day I crawled under it and noted the 2 lines plugged into the transfer case just didn't look right. I reversed them and had one of those AH, HA moments when I got back inside and drove it. It was an expensive lesson.

 

Does anybody else's truck make a hell of a clunk when bringing it out of 4wd high back to 2wd?

Mine does it anyway I try it....Neutral in the driveway stopped or rolling....either way it's a hell of a jar I think.

Of course dealer said "that's normal, they all do that."

 

Normal. Doesn't always do it but when it does it is nothing to be concerned about.

 

When vehicles are idling, they don't use all that much fuel, some but not that much, and from what I understand this new engine probably uses even less.

 

But it still reduces your mpg reading

 

No where as much as from 13 to 22 mpg, unless it sat for days. When I was younger my aunt left her car running over night once, probably over 12 hours, and she said it hardly used any gas.

 

It still uses gas. Sure a car can idle for a day or two with a full tank, just using my remote start in the winter and my average dropped 2-3 mpg in my f150

 

Ya but we're talking about an "efficient" engine here, again no way it dropped it from 22 to 13 mpg

 

This has happened to me in my 16 TRD OR. But I was on the trails trying to get it to disengage for a good 20 minutes. I wish we could go back to manual hubs and stick t-cases. Never had issues with those.

 

UPDATE

I have gone from the best average of 16/19 on the highway to 28.8!. That is a huge jump. In the city I am getting between 15/19 depending on how aggressive I am. I feel the city is pretty normal and I am stoked about the 28.8! I am more convinced that the 4x4 system was being wonky.

My 4x4 blinks sometimes when I put it in neutral and switch from 2wd to 4wd hi. when I drive the light will go solid and it feels like I am in 4x4. Does your 4x4 go solid light as soon as you switch or do you need to drive to get it to engage with this truck? I watched a video and it didnt blink on the video but mine is now blinking for a bit till I drive and then will do solid.

 

Mine made a nasty clunk/grinding noise when I switched back and forth but only one time.. Now it just makes a click

 

FWIW, my 03 frontier wouldn't go out of 4WD back to 2WD, despite the light going off. I would have to stop, put it in reverse, back up a hair, go forward and the front hubs would unlock. Different truck/driveline entirely, but it's certainly possible that the checks for being in 4WD and engaging the light are imperfect.

 

It blinks while its switching and solid when it's locked it. sometjmes in neutral it take a min to sync. It's designed to be shifted in fly meaning it can be engaged while moving under 60 mph. You only need to be in neutral for 4 low

 

First I want to state that I have a Gen 1 and the link I'm posting is for a Gen 2 and I believe y'all are driving Gen 3's. The Transfer Case Actuator looks to be the same (in pictures) in my Gen 1 and the photos of the TC Actuator in the Gen 2. So maybe it is similar in the Gen 3. My Gen 1 Differential Actuator (ADD) looks similar but has some electrical difference than the Gen 2. It is possible the Gen 2 and Gen 3 are similar. This link has a lot of great info in it relating to engaging four wheel drive. Sadly it's not just pulling a lever anymore. When you select 4 hi the transfer case actuator locks in the transfer case then the ADD slides a collar onto the right side axle locking the axles into four wheel drive.

Give this a read for better understanding. If anything it is good to know that Gen 2 front ADD has a weak link and maybe something to look into early on the Gen 3's to understand preventative maintenance or just getting stuck because it failed when it was needed. From the pictures I saw in the posts the weakest link is the vacuum hose will crack and allow moisture into the ADD and corrosion will do its worst. On my Gen 1 at 237,000 miles the TC Actuators vacuum hose broke and let moisture in. I was able to "rebuild" the TC actuator and my four wheel drive is working again. I took the time to inspect and "rebuild" (though it wasn't needed) the ADD too and now I hope to have another 237,000 miles out of these components.

https://www.tacomaworld.com/threads/how-to-trouble-shoot-4x4-actuator.263525/

Sadly though 4 hi is no longer you're either in it or you're not...

Here is a link to the post I just put up with info on the internals. While the parts may differ Gen to Gen the concepts are similar enough I think the info will be useful.

https://www.tacomaworld.com/threads/4x4-actuators-gen-1.456059/

 

Only other thing I don't get is he's mentioning locking hubs? It's auto locking hubs so wtf?

 

4 pages of input, still doesn't follow instructions on card in visor/owners manual, on engaging 4hi from 2hi

 

Ultra Gauge says my 2.7 l 4cyl uses about 0.25 gallons per hour idling with the a/c compressor not engaged and 0.48 gph with the compressor running.

 

Sometimes it will engage right away, other times you have to roll forward or backward a bit for it to sync up. It's normal. Same goes for the e-locker if you have the TRD OR package.

Mine sometimes makes a loud clunk/clank when engaging or disengaging, other times it's just a small "click". Also normal as far as I can tell. When it's a louder "clank" it feels like there's tension releasing causing the noise, I always try to engage/disengage after rolling in a straight line for a few feet. Never with the wheels the turned