Using Factory Differential and Transfer Case Settings (1 Viewer)

[jjcobm]

Hi everyone,

I have question regarding the factory differential and transfer case settings (i've never had a reason to use them). I've read the owners manual dozens of times, and also have searched on this forum in regards to my questions, but what I find is not exactly what i'm looking for.

First off, my owners manual states that when using the differential lock settings, that you shouldn't drive the vehicle above 5mph. Now my question is, is this really true and if so, then what use would the differential lock option have if you can't go any higher than 5mph when using them? My guess is that at that speed the only use they would have is in a rock crawling situation? If someone can explain to me what the real world uses for the factory differential lockers are I would really appreciate it, it's been puzzling me for the longest time.

Secondly, the factory transfer case has three settings. High, neutral, and low. Reading some of the threads on here, i've been able to find that the High settings is (obviously) used for everyday driving. From what i understand, the high setting is basically AWD but without the center differential lock engaged. The low setting is AWD with the center differential lock engaged, yet it disables the ABS. And the last setting is nuetral which basically does not transfer power to the wheels. Now, the owners manual does not recommend that you drive (as a daily driving) on the low setting and if i remember right the speed limitation on the owners manual for the low setting was either 15-20mph. The owners manual also fails to tell me the real world uses for low setting and the nuetral setting. My question regarding this is, when exactly would the low & nuetral settings be used for in a real world situation, and what are the speed limitations to these?

Thanks in advance!

 

[Sarmajor]

The neutral setting is there just because there has to be a neutral position between Hi and Lo.
If you do not have a CDL switch then you can only engage the center diff lock by putting the transfer case into Lo. This also disengages the ABS. Not sure about others but sometimes you really do want to lock up all the wheels when out wheeling. I couldn't think of anything worse than rear ending someone because the ABS was doing its thing in a gravel situation.
The Front and Rear diff locks will not engage unless the Center Diff Lock is engaged and the dash light is on.
(Had a vehicle out on the weekend that had had it's transfer case replaced abd they did not plug the switch back in so he had Center Diff Lock but no Front and Rear until we found the plug and connected it)

Dont know about others but I have had my truck in top gear in Lo ratio and you can get up to about 35mph. Sometimes it is just not worth changing to Hi ratio for the short trip between hazards.

 

[jjcobm]

Thanks alot for the info!

I had no idea it was safe to drive in the low range above 20mph. Makes sense that the abs be disabled on gravel surfaces. Although I do have one more question about the transfer case. When would you be in a situation were you would have to use the low range? The FJ80 is a very well equipped vehicle with it's unique AWD, and i've never yet had to switch to the low range, and i've been in deep deep snow before. Crawls through like a beast.

As far as the differential locks go, can anyone confirm the uses for the factory differential locks, in a real world situation, and the speed limitations, if any, when using the lockers?

 

[OGBeno]

To engage the lockers, you should be at 5mph or less, then you can let her rip!

[figuratively, of course]. If you are locked, I doubt you'll be going very fast anyway--10-20mph max.

 

[vkfzj80]

I think that some of the uses for the lockers would be steep inclines that are slick(sand, snow,ice, mud), sand, mud and all the other cituations where you need maximum traction.

keep in mind that having lockers ingaged while driving puts a lot of stress on the drivetrain, and manuvering tight trails with front locker engaged can be a challenge in itself because the vehicle doesn't want to respond to streering very well

 

[CJF]

When would you be in a situation were you would have to use the low range?

You've never gone up something steep enough that it would have been nice to have had a lower gear?

Plus, you say you've crawled/driven through deep snow. Chances are you would have been better off having the TC in Low and letting the engine rpm's stay up (in the 2-3k range, say) and the tranny work through its gears rather than just plowing along in 1st with the TC in High. That's a perfect way to overheat (i.e., kill) your tranny.

Curtis

 

[dace voit]

Normal driving on any road or surface without obstacles (things that you want to go less than 10 mph over) is when you drive with the TC in HIGH.

"Off-road" driving, when you must crawl or go very slowly over, around or under obstacles, lest you increase the chances of damaging your vehicle is when you drive with the TC in LOW.

The lockers you then use in situations that require even greater traction.

The reality is that the conditions dictate the gear in which you drive. Much of this is just experience, and you will have to learn by getting into it.

The quote about destroying your tranny is true, when you are in LOW, there is no need to drive fast. It is there to get you through technical situations. I always am driving slowly, and being patient. I am anal about my ride that way. If you are driving in the wrong gear, you will generally be able to tell. ie. engine revving too high, or the engine laboring needlessly.

Sorry if I am making an incorrect observation, but it does not sound like you do or have done much driving "off-road". If I am correct, then HIGH is position you will drive in most, if not all of the time. Don't be fooled into thinking that LOW will be better for any condition like snow packed roads or rainy conditions. As far as muddy conditions, most of the time you are already driving off-road anyway.

I hope this answers your ???'s

 

[jjcobm]

Thanks for all the info guys!

That answers all my questions there.

It is true, i haven't done much offroad driving, which is why i asked this question. I just got this truck last summer (first SUV i've ever owned), and have been working on it since. I wanted to have a clear understanding on the different funtions each gear/setting had before I start to do some real off roading, and not end up stressing the drive train.

The part about snow, really makes sense, i did have the TC set on high, but didn't think of the fact that it would have put less stress on the drive train if i used the low setting and just let the transmission do it's work and keep the rpms on the low range. I haven't/didn't run the tranny long periods of times, neither did i have it on first gear (had it on drive all the way through), it was pretty much jumping between 2nd and 3rd gear as i was crawling through deep snow (did not want to get stuck out in the middle of nowhere ), but i do understand that using a low setting in that situation would have been a better option and kept the transmission cooler.

Thanks alot guys

 

[harper68]

diff lock

It is good to exercise your low range and diff locks on occasion to keep them working properly. Just do it on dirt or gravel roads and try not to steer too much when the front diff is locked. The motors get sticky if not used much. Once a month would be good IMO.

 

[IronYuppy]

This is the best explanation of how the 80 Series diffs work, that I've ever seen. It took this for me to understand the centre diff lock.

http://www.safari4x4.com.au/80scool/george_couyant/diffs/diffs.html