It started about couple of weeks ago, when I start driving my 2003 GX470 it would make a loud rattling noise only in the first gear. If I press the accelerator hard it made a metal hitting the metal noise but if I gradually increase the speed it would do fine in first or any other gear. I didn't think much of it and drove to Pensacola (from Atlanta) for the weekend, I did about 70 without no issues. During the trip I had no issues at all only when I stopped at the red light or at stop sign it would make the noise if I accelerate harder.
I brought the vehicle back to Atlanta and took it to my local mechanic (not Lexus/ Toyota specialist). He test drove it and end up putting the vehicle on the lift. He determined the noise was coming from the Transfer case so he took the shaft that goes from the transfer case to the rear axle. It was attached with 4 nut bolts on each side. He suggested I look for the replacement transfer case and he will replace the TC. Currently that shaft is sitting is in the back of my truck. I drove the vehicle from mechanic shop to the house yesterday and it was making some weird noises. This morning when I drove to the airport my vehicle was making some weird noises again and at one of the traffic light it almost felt like the back end of the vehicle wanted to come out of the vehicle.

I am wondering about the following and would love to hear your expert advice,
If I am not planning to use the 4WD, do I need a new transfer case?
Is it safe driving the vehicle when that shaft is not attached?
New TC is around $2800 and I can get a used one with 90 days warranty for $1500. Labor to install is around $600. Is it worth replacing or can I get the TC repair with the Rebuild Kit?
Is there one rebuild kit better than the other one? What are your recommendations?

Where can I find a decent price transfer case? Is it better to repair the existing TC or get a used replacement?

I added a video so you all can hear the terrible noise it makes only in first gear.

Any help in this matter would be highly appreciated.

 

If you're going to drive with one of the driveshaft's removed, you need to lock the CDL so the center diff is sending 100% of power to the remaining driveshaft, and not trying to manage a torque split and burn itself out. With the rear driveshaft removed, it thinks the rear tires are slipping.

 

Thank you for replying and I appreciate it. How I would be able to lock the CDL? is this something I can do or mechanic have to do it?

 

Unless, I misunderstand, you just push the center differential lock button. It's the button with wheels and axles on it

 

CDL button is the "4x4" button, on my truck it's next to the heated seat switches in the center console, on some other years I think it's over on the left of the steering wheel by the mirror adjustment buttons.

 

First -- see if your mechanic checked for metal shavings in the transfer case fluid. If it hasn't been serviced every 30k miles like it should have, the old fluid would have allowed excessive wear of the toothed belt inside, and it self-destructed. Replacing the fluid with fresh might get you a little more life out of it (no guarantee).

You won't be able to drive without a transfer case unless you get a custom rear driveshaft made, as the factory driveshaft won't be long enough to reach the output shaft of the transmission. There will also need to be a custom driveshaft yoke made too (probably) to fit the spline pattern of the output shaft. This would be RWD only, as the front driveshaft would have to be removed. So no 4WD capability.

Choices are: You can either replace it with a used one from a parts yard, or a factory remanufactured one from a dealer, or declare the vehicle as mechanically totalled (sell it for parts or as a "handyman special") then buy a new vehicle.

Chip H.

 

@chiph9 Thank you for the post and I appreciate the insight. Following are the updates,
1. When I took it to a mechanic about two weeks ago for diagnostic and he removed the rear shaft, at that time I replaced fluid in both differentials and in the transfer case. (unfortunately when I did a test run with the shaft again, it was making a noise so shaft was removed again)
2. Since removing the shaft, I drove it to Pensacola(FL) from Atlanta(GA) and back to Atlanta with no known issues. I been using the vehicle locally and haven't seen/felt any problem with it.
3. Lowest price used TC I found is around $1400 and it came from the vehicle that had 167000 miles already. It only have 90 days malfunction warranty that doesn't cover the $600 labor charges. I did find around $2800 brand new TC from Lexus dealership that have one year manf warranty.
I also reached out to one local mechanic who is suppose to be a best in the game for transmission and transfer case. He is working on a quote for me, hopefully if he can rebuild it under a $1200, I think I would be in much better shape.

 

This isn't the same exact transfer case that is used on the GX, but it's related (from a 4Runner).
This video will give you an idea of whats inside.

 

Odd that it seems to work ok at 70mph, but from a stop it has issue. Almost sounds like the actuator is trying to engage but can't, but at 70mph the actuator should be cutoff from engaging.

Post #6 is where a mechanic has to go. Need to investigate the case oil. Does it even have the correct amount of oil? Drain the oil and start looking. If it has obvious chunks or shavings of metal, than that is likely a bad issue. If the oil does not show chunks or metal shavings then I would send the oil for a UoA (Blackstone or the like) and note for them the issue, they can test for specific things that may suggest a shot bearing or other.

But has it been determined that the issue w/ the case seems to be driving the front shaft? I am wondering, w/ no need for 4x4, can mechanic open the case and remove the parts that drive the front shaft?

What is kinda crappy in design is that it's one case for both front and rear drives. I wish they would use a dual case system where the case for front drive is driven by the case for rear drive, this way if the front has an issue you can remove it and perhaps just plate off the where they mate.

 

Here is an update, I went ahead and purchased a new Transfer case from Lexus, it came with with the complete Module and all the wiring. In my honest opinion, its worth $2780 for the peace of mind at least for one year compare to the used salvage Transfer case for $1550 that came with 90 days PARTS only warranty. I paid $700 for the labor to install. Here are the pics. If you are planning to upgrade with the newer or used TC, don't forget the seal that goes in between the TC and Transmission.

 

I love shiny new parts.

Glad you got it working again.

Chip H.