HDJ81 transfer case will not shift into 4Hi (1 Viewer)

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Yesterday we took our 5-speed manual 1991 HDJ81 out on some 4wd roads. We had been using both 4Hi and 4Lo, depending on the terrain, throughout the day. Towards the end of our trip I tried to shift back into 4Hi using the transfer case shifter (H-N-L), but was unable to no matter what I tried. When I shift the transfer case I make sure to stop completely and depress the clutch. So, to get home we ended up having to trailer our HDJ81 home on a friend's trailer because we could not get the transfer case to shift into 4Hi to be able to go highway speeds.

Everything works great in 4Lo, no problems. The CDL (center differential lock) dash light behaves as it should when shifting into and out of 4Lo: the CDL light turns on automatically when you shift into 4Lo, and goes out when shifting out of 4Lo. The thing is that I cannot shift into 4Hi...very frustrating. The transfer case shifter lever will allow me to shift into what seems like it should be 4Hi, but then when I put the transfer case shifter into 4Hi and then release the clutch to go into gear (1st or Reverse) it then makes a weird whinning/grinding noise and I do not move at all. For comparison, I am able to shift into multiple gears while in 4Lo.

In terms of troubleshooting I checked the transfer case fluid and needed to add a little bit of fluid. Topping it off did not fix the problem. I have also torn into the shifter area, but stopped once I got to the rubber boot that is beneath another boot. I thought perhaps it might be a linkage issue.

Does anyone have an idea on what is going on here? I have found numerous threads of people not being able to get into 4Lo, or no being able to get out of 4Lo...I can do both. I just can't get into 4Hi and therefore can't drive on main, paved roads! Suggestions?

Thanks for any advice!
 
Joined
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The transfer case gets used in 4Lo maybe a few times a month, some for travel including off-road, and sometimes to back a trailer up in a tight spot. Regarding the recommendation of trying WD40 or something...where do you recommend I spray it @roscoFJ73 ?

Below is a photo of how far I tore down the transfer case shifter. The rubber boot that is there in the photo is torn and somewhat brittle. I won't be able to remove the boot without ruining the boot in the process. Thoughts?

HDJ81_transfer_shifter2.jpg
 

SNLC

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Access linkage from below. You won’t even really be able to get at it very well from above. From below you can easily unhook the linkage and try shifting the tcase by hand at the lever on the tcase. All the way forward is low, all the way back is high. It’s opposite the shifter in the cab on the tcase lever.

If you have been using it regularly it’s probably not linkage though, stuck and seized linkage as well as the lever in the top of tcase usually occurs from lack of use.

You can try putting it up on jack stands or a lift. With no load on the drivetrain it may shift out. Try turning the output flanges while you try and shift it. If the linkage is good and the lever on the top of the tcase is good then it is likely internal.

Cheers
 

SNLC

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After additional research on the issue it looks like this thread captures exactly like what I'm dealing with (see Help! Low Range But No High Range - https://forum.ih8mud.com/threads/help-low-range-but-no-high-range.653134/ ) One of our knuckles is leaking, so it is looking like a drive flange has stripped. Argh!

I personally have never seen this be the cause of a tcase stuck in low. Not saying it can’t happen though. Usually stripped drive flanges cause a “thunk” when put into gear.

Here is what wasted drive flanges look like, this one was let go for so long it has also trashed the birfields.

5BD29EE9-5550-484E-8856-8190A09C99E8.jpeg

3773B931-B842-4977-A4C8-3A40832894E8.jpeg


It only takes about 15mins to check the drive flanges so you could certainly do that in your trouble shooting process.

Cheers
 
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Thanks @SNLC ! Sounds like I need to check the drive flanges first and then see what to do next. I am new to the birfield/drive flange thing, but I know there are countless excellent resources of how to do this at home, DIY. The transfer case lever has never been difficult to shift and was no different when this issue of not being able to engage 4Hi popped up. It is not so much that I can't get out of 4Lo, it is that I am not able to move when in 4Hi...it just makes a grinding/whirring sound. We noticed that the front driveshaft spins with no resistance when in "4Hi" but the manual transmission is in neutral. That fact made me think that it is an issue with the drive flange/birfield, as linked earlier in my previous thread. I wouldn't think the slowly rotating front driveshaft thing would happen normally.
 
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Messages
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Thanks to @SNLC , after taking off the drive flange on the JDM driver's side (aka the US passenger's side) we discovered that we indeed have a stripped, or well worn, drive flange. Our birfield is also worn as well, so both the drive flange and birfield will need replacement. I have added some photos below of what we found. Please let me know if I am off here.

Also, for those that are following this thread, we are able to drive the vehicle in 4Hi if, and a big if here, if we engage the center diff lock (CDL). I guess because the drive flange/birfield interface is no longer functional on at least one front wheel, that having it in 4Hi with the CDL engaged does not damage the drivetrain, correct?

So, to summarize, what seemed like the inability to shift into 4Hi is not actually due to a transfer case issue...but rather due to stripped drive flange/birfield interface issues. Hope this helps other folks!

I will now be looking into redoing our 1991 HDJ81's knuckles/drive flange/birfield :) Through research on other ih8mud threads about LC 80 knuckle rebuilds it appears that the 95+ Land Cruiser birfields and drive flanges are slightly longer and offer slightly more wear surface for hopefully a longer lasting birfield/drive flange. Is this correct? And that I would be able to get 95+ LC 80 birfields and drive flanges, but all the other parts (i.e. the knuckle rebuild kits) will work just fine? No special studs or longer bolts or anything like that?

DriveFlange_1.jpg



DriveFlange_2.jpg


Birfield_1.jpg


Birfield_2.jpg
 

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