4wd Issues

Hey all. 2005 Tundra SR5 4.7 stepside. From my previous posts you will see I have done a ton of work on this truck to get it back to where it should be. The other day we got some snow so I pushed the 4hi button while going straight down a road at 25mph. Both 4hi and 4lo buttons and dash lights are flashing. I've tried stopping, putting it in neutral, trying to turn it on and off at different speeds, nothing works. Today I took the negative battery cable off to see if I could reset the system but no luck. From what I can tell the truck never actually engaged 4wd since no lights have ever been solid and I didn't hear anything activating under the truck. When I drive it around and let off the brakes, the truck feels a bit like there is drag on it, almost like it would be in 4wd. If it was warmer I would be under the truck pulling everything apart but alas winter is here. Any thoughts on what could be going on? Is there a way to deactivate the system for now and just not use 4wd until I can get under the truck once it's warmer. Backstory: the truck was sitting in Florida for a year before I shipped it back up here. Original owner was my mom so I know all that's been done but I know these beasts have issues if you don't run the 4wd from time to time. TIA

 

So you think it’s stuck in 4wd and won’t come out? How so if it never actually engaged? Does it continually blink and not turn off?

I’m not sure of a way to disenage it manually if that’s the case but I’m sure one of our other members do.

 

I am not sure if it's stuck in 4wd. The truck just felt different like it had some drag on it. Can it partially engage and get stuck that way? It continually blinks no matter what. I even tried the 4lo button and nothing.

 

Sounds like it wants to but it can’t. If it doesn’t bind going around corners, you’re probably okay although it would be inconvenient for it to suddenly engage and get stuck in 4wd. Weird that it won’t stop trying.

 

If my memory serves correct, when both 4HI and 4LO lights are blinking, that means that the truck thinks both the transfer case actuator and the front differential actuator aren't in the correct positions. When I went through the 4WD ordeal on my truck, I shifted the transfer case manually with the actuator removed, to ensure the position switches were working. When I did this both 4HI and 4LO lights blinked until I put it back in it's correct position.

You might be able to get some answers from the piece of paper on the visor that has information on the 4WD system. I don't think there's an easy way to disconnect the 4WD system and with the drag you mentioned I'd be hesitant to continue to drive it around in case it might be in 4WD, especially if you need to drive on dry pavement.

My guess is that one of the actuators has shifted but the other hasn't, or maybe they have shifted partly and become stuck.

Here's what I'd do: get under the truck (I know, it sucks in the winter) and see if you can manually turn the front driveshaft with your hand. If you CAN turn it, then neither your transfer case actuator or front differential is engaged in 4WD. If you CANNOT turn it, then at least one of the two actuators has shifted into 4WD.

If you CANNOT turn the front driveshaft, I would then jack up the front of the truck and see if you can spin the front wheels separately. If the front actuator is engaged, when you spin one wheel forwards the other will spin backwards. If the front actuator is not engaged, you will be able to spin the front wheels individually from each other. If you can spin the wheels individually, then the front actuator is not engaging properly.

 

Ok once it stops raining here in NJ my plan will be to go under and take a look. Do you have that process written up that you used to remove the actuator and shift it manually? Eventually I am going to have to tackle this whole project. I'm assuming actuator replacements are in my future to fix this?

 

The reason I shifted the transfer case manually was simply to ensure that my transfer case moved at all. The 4WD in my truck hadn't worked for 10+ years, so I was making sure the transfer case internals weren't messed up. I wouldn't recommend shifting your transfer case manually unless it's in the wrong position due to an actuator failure.

It's very common for the actuators to get corroded on the inside and stop functioning because of it. It's very possible that you will be able to remove the actuators, disassemble them, clean them, and reinstall, instead of buying new ones. Unfortunately new ones are expensive, and like most other items for our trucks, OEM is the only way to go. Trust me. If you can save your original ones, that's best.

Let us know what you find once it stops raining. I'll walk you through any further actuator removal/diagnosis once you've investigated, if needed.

 

From the little that I know about the 4WD system in the Tundras, the transfer case actuator can only be removed by opening the transfer case. That is a big and expensive job. However, if the issue is not internal within the transfer case, it's usually the cap to the actuator (looks like a distributor cap) that's the problem. The cab be can removed without disassembling the transfer case, cleaned up internally and reinstalled. If the contact ribbons inside the cap are shot (corroded), the cap is usually too far gone. That is exactly what happened to me. The cap was too far gone, cracked housing, contaminated inside, etc. and I put the final nail it when I tried to remove the rusted screws. I bought a new actuator (non-OEM,not too expensive) and used the cap but didn't use the shift rod that it came with since replacing that part would have required opening up the transfer case. Teh original shift rod was fine and I was able to manual engage 2wd and 4WD Hi without a problem. So I simply replaced the old cap with the new one. It was a bit tricky to install the new cap because the internal gears had to be in the correct position. There is a YouTube video on removing just the cap. I was able to get my 4WD-HI working again and it goes back to 2WD with no issue. I'm still having issues with 4W-LO but I 'm on Long Island and it can wait until the weather warms up before I give it another try. I believe my remaining issue is electrical because the front actuator seems OK. I had to clean it up too and there is a small wire harness that I had to replace. I wish these Tundra just had mechanical shift to engage 4WD Hi and LO. All this electrical and ECU crap makes a big problem out of something that should be very simple.

 

You’re right, thankfully the plastic cap can be removed and replaced pretty easily, which is awesome since that’s what is most commonly the issue.

One thing though- it is possible to remove the actuator without opening up the transfer case.

It requires dealing with three tiny 8mm bolts on the very top of the actuator and are not only hard to see, but super easy to snap. Removing these bolts allows you to remove the actuator assembly separately from the shift rod, which can stay in the Tcase.

 

Well here's a potential cause of the issue....
This hose which I am assuming is a vacuum line for the system was dry rotted off. I checked the front drive shaft and it was free spinning. I fixed the line, started the truck and no 4hi/lo lights anymore. Now that I confirmed it's not stuck in 4wd I'm going to leave the system alone until it gets warm out again and then I can further mess with it. Chances are it might need to be cleaned up but at least the light is off.

 

Glad to hear that your lights have gone away!

That hose is actually just a vent line, not a vacuum line, but that’s really good that you caught it. That’s usually the source of water intrusion into the actuator which causes the corrosion and actuator failure that is so common.

The hose runs to the engine bay and connects to a vent fitting attached to the inside of the driver’s frame rail.

 

I don't believe that's a vacuum line, just a vent tube. If vacuum, where is it pulling/creating vacuum from? I guess that's my biq Q?

And yes, this should be on the list of things to maintain with 4WD. I've been meaning to run up the part number on it, or take an OD/ID/wall thickness measure on it to get a replacement.

 

I had a similar issue this fall. When i took apart the rear actuator mine had a lot of corrosion on the contact strips. I just used a wire brush to clean it up a bit and then put some dielectric grease on and it worked like a charm!