NP231J / NV231J Transfer Case Operation (Shifting Specifically)

[RaymondT]

I assumed that you could simply pop the TJ into 4hi and back to 2hi and life would be grand. Now I'm not so sure.

Recently, I discovered quite by accident, slightly higher gear noise when I shifted back into 2hi. The linkage is properly adjusted and the 4WD light does go out when you put it in 2hi, but I find the need to stop and back up 5-10ft before I detect the subtle clunk of it totally disengaging. I did a master kit a year or so ago and the internals were spotless.

Out of curiosity, I took a look at my original owners manual and they mention "To reduce shifting effort, drive vehicle in reverse for a few feet, or drive off the hard-surfaced road momentarily to allow tire slippage." The statement is kind of vague and it doesn't specify what action you attempting with the transfer case.

Is anybody else finding the need to back up?

 

[Blackjack]

Too dry a surface or an imbalance in tire diameters will lead to drivetrain windup. One trick is to shift the tcase similar to how you would clutchless shift a manual trans.

 

[billiebob]

So in 4WD the transfer case has no differential. It will pull into 4WD fine but shifting into 2WD if there is any gear bind, it will not shift until that bind disappears. Often just turning a few corners will remove the bind. The shifter in the TJ preloads a spring which will automatically shift once the bind is gone.

The reverse thing goes back to 4x4 from 30 years ago. There was no pre load back then and the lever would not even move if there was any bind. That plus in old Fords, the front axle was a 4.10 ratio and the rear was a 4.11 ratio. Driving forward the bind was always there and a howl was noticeable on the highway. Reversing 15' would relieve the bind and with a hand on the shifter it would move effortlessly into 2WD.

Anything to remove the bind will let the shift happen.

 

[LukesfirstJeep]

That plus in old Fords, the front axle was a 4.10 ratio and the rear was a 4.11 ratio. Driving forward the bind was always there and a howl was noticeable on the highway. Reversing 15' would relieve the bind and with a hand on the shifter it would move effortlessly into 2WD.

Has this changed on Ford made in the century? My FIL, drives Fords, and he still backs up when going to 2WD from 4WD. His actions might be old habits.

 

[Jerry Bransford]

Reversing 15' would relieve the bind and with a hand on the shifter it would move effortlessly into 2WD.

Which hasn't been needed in many years, it definitely is not needed for any of our Wrangler transfer cases. Driving with neutral throttle and perhaps an s-turn or two is all that's needed to help it get back into 2wd more quickly. Accelerating/decelerating in an effort to speed the process is counterproductive and only makes it take longer to shift back into 2wd.

 

[KCNoDots]

My older buddies used to say that you had to back up 15-20 feet after going back into 2WD to "unlock the hubs". I am not sure how true that is.

 

[StG58]

So in 4WD the transfer case has no differential. It will pull into 4WD fine but shifting into 2WD if there is any gear bind, it will not shift until that bind disappears. Often just turning a few corners will remove the bind. The shifter in the TJ preloads a spring which will automatically shift once the bind is gone.

The reverse thing goes back to 4x4 from 30 years ago. There was no pre load back then and the lever would not even move if there was any bind. That plus in old Fords, the front axle was a 4.10 ratio and the rear was a 4.11 ratio. Driving forward the bind was always there and a howl was noticeable on the highway. Reversing 15' would relieve the bind and with a hand on the shifter it would move effortlessly into 2WD.

Anything to remove the bind will let the shift happen.

Which hasn't been needed in many years, it definitely is not needed for any of our Wrangler transfer cases. Driving with neutral throttle and perhaps an s-turn or two is all that's needed to help it get back into 2wd more quickly. Accelerating/decelerating in an effort to speed the process is counterproductive and only makes it take longer to shift back into 2wd.

SE's have that same, slight, gear mismatch. Unload the drive train and push or pull the happy lever as required. Done. 4lo is a different story.

 

[Jerry Bransford]

SE's have that same, slight, gear mismatch/

The binding is not caused by the .01 ratio mismatch between the front and rear axles, like 3.73/3.74 or 4.10/4.11. Rubicons have the exactly same issue yet their axle ratios match exactly since their f/r axles are the same. Even when the ratios are identical, as is with the Rubicon, there will be drivetrain binding caused by the front tires needing to rotate faster than the rear tires in any kind of a turn, even a very slight one.