Transfer case 4LO not engaging?

2001 TOYOTA TUNDRA
350,000 MILES • 4.7L • V8 • 4WD • AUTOMATIC
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WESTONADAMS
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Hello!

I listed this truck as having 350,000 miles, but this there is a caveat. The Carfax has some unclear information about it, and we really don't know the mileage. The frame and underside of the truck are in great condition. No rust whatsoever.

But regarding the issue I'm having.

I recently purchased this truck. The previous owner had just replaced the 4x4 actuator. And the 4x4 was working when I purchased it.

Now I am having some strange symptoms. The truck shifts fine into 4Hi, but when I try to go into low range, I run into problems. I am following proper procedure (go into neutral, etc.,) according to the manual, but when I shift from 4Hi into 4Lo, one of two things happens.

1) Occasionally, the vehicle goes into freewheel. Basically neutral. From my research, there is a "freewheel" section in the differential between high range and low range. So apparently the truck is getting stuck halfway between high range and low range.

or 2) more frequently, I hear a humming sound coming from the 4x4 actuator. When I put the truck in gear, the humming sounds turns into a buzzing sound that sounds like the plastic gears in the actuator are grinding in an attempt to shift into low range.

It appears to me that the transfer case is having difficulty shifting into low range. This is probably what caused the previous actuator to go bad. And it looks like it's doing the same thing to the new actuator.

My guess is that the 4x4 on this truck has rarely been used. And I don't know if the transfer case fluid has ever been changed. So, the components in the transfer case may be seizing up from non-use and low maintenance levels.

The only thing I know to do is to check/change the transfer case fluid and see if things start to move more freely. I may have to replace the 4x4 actuator again as well. But I would value any input from those with more experience.
Oct 31, 2023 at 4:57 AM
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STRAILER
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Yep, I would start by replacing the transferase shift actuator because you may have got a defective unit which is common with inexpensive parts. Here is how the job is done, if this doesn't help the transfer case is worn out and needs to be rebuilt. Check out the images (below). Please let us know what happens. I can send you rebuild instructions as well.
Oct 31, 2023 at 10:46 AM
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WESTONADAMS
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Okay. So, do you think the problem is caused by transfer case fluid that has never been replaced? Or maybe old fluid doesn't cause these symptoms...
Oct 31, 2023 at 5:42 PM
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STRAILER
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The old fluid I don't think will cause this problem, but it is easy to change out. please check out this guide to help you see how to service the transfer case:

https://www.2carpros.com/articles/how-to-service-a-4x4-transfer-case

Please go over this guide and get back to us.
Nov 1, 2023 at 9:29 AM
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WESTONADAMS
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Just as an update, I opened the transfer case actuator. Apparently it may have been a cheap defective unit, because it was jammed up inside, and it looked like some of the electrical connections had some kind of glue on them that was preventing contact. I fixed the metal that was jamming (by bending it so it didn't jam) and sanded the contacts down to bare metal. Everything works now. Yay! I'm grateful and blessed.
Aug 31, 2024 at 7:30 PM
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STRAILER
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Nice work!,, it can be tough when you replace a part and then it still doesn't work and then start looking around for other things. Thanks for letting us know, we are here to help, please use 2CarPros anytime.
Sep 1, 2024 at 10:46 AM