diff locking questions...

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Apr 6, 2008
I've been doing some reading around here on the rear diff elocker, and found this thread: https://forum.ih8mud.com/100-series-cruisers/75494-98-99-rear-diff-lock-high-range.html that gives good instructions on how to make the rear locker run in 4Hi. There was a comment that made it sound like a similar procedure had to be done to the center diff to get it to lock in 4Hi. The thing is that my center diff seems to work in 4hi, at least the light comes on solid. I can't find anything else about it, which makes me think it might have just been a bad inference by me.

On a related note, has anyone found any negatives to modifying the rear locker to work in 4hi mode? I'm really just thinking about the snow here and the poor quality of snow removal (or lack thereof)... Thanks everyone.
Seriously? Nobody has any input for me on this?
I take it you have an early 100 with rear locker. What do you mean by the CDL comes on in High? You mean by hitting a switch, not all the time, right?
more_boost, adding your model year to your signature would help. I vaguely remember the CDL in HI range mod only applies to the 98-99. Later years don't need the mod as the CDL can be switched in HI already.

Correction: CDL can be engaged in HI (and LO) in all years. It is the CDL disengagement in LO that requires the PIN-7 mod in the earlier 100's. Late model 100's can do this w/o mod.
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I guess that would have been key info, but I didn't realize there was a difference in later 100's. yes, I have a 98 100 LC. Yes, by hitting the switch, the CDL will come on in high range. My primary question, which I haven't found an answer to in searching, is whether or not this causes damage to the components. More concisely, is it a safety feature for the driver or the gears? I can see how toyota wouldn't want people to be running around with the rear diff locked at highway speeds.
I guess it would be a safety feature. Locking the rear diff at speed when you were doing a lot of turning would definitely cause some issues.
The Center Differential Lock (CDL) can be lock by the switch in high range. When you shift into low range, the CDL automaticlly locks in the 98 & 99's. The 7 pin mod makes it so you can run in low range WITHOUT the CDL locked. You can also do a mod to falsify the low range signal to the rear locker control unit so it will lock in high range. I did this to my 98 and just liked having the option of using the locker in the snow or mud and still have high range. When you do the mod for the locker in high range, the over drive will be locked out in high range. I'm working on a switch over ride at the transfer case to do the same thing, just a shorter route for the wires to the console. I'll post up when I get it done.
Being able to lock the center diff in 4HI makes it work the same as all part-time 4WD systems like you'd find in 60-series or earlier LCs, Tacomas, minis, etc. Normally, your center diff allows varying amounts of torque to be split between the front and rear axles, as the differential sees fit. When you lock it, making it function like a traditional trasfer case, that splits the torque equally to both the front and rear axles. I've never driven an AWD equipped vehicle (on or off road) so I don't know how they drive compared to part-time 4WD systems. Having said that, I would not lock the center diff if the roads are dry, just as I would never shift a T-case into 4HI on dry roads. You need to have a little bit of differential slip between the front and rear tires that results from wet/icy asphalt or dirt roads to keep the locked center diff (or T-case) from binding up and breaking.

Regarding the rear locker, I can't think of any time when it would be a good idea for the locker to be engaged while in 4HI. It would likely cause extreme handling issues on all but the slickest roads. Any surface where the tires have good grip you would have a very difficult time turning and the binding in the locked rear differential would most likely cause severe damage.

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