Jeep nv247 transfer case stuck!

[lars11]

The 4wd selector on a friend's jeep is completely stuck. It is a 1999 Grand Cherokee with the nv247 transfer case. The Hi mode works just fine, but it is impossible to move the selector to either neutral or 4Lo. The case fluid was recently changed using the mopar speciality fluid.
How to make the transfer case shift again? What to do?

 

[unDummy]

Check/lube the linkages.
Rebuild the transfer case.

 

[Slick 55]

Find an empty parking lot and drive figure 8's for about 10 minutes. It's an old Jeep trick.

 

[Zaedock]

Clean the shifter linkage.

 

[lars11]

Ok, thanks. The wire is lubed and moves freely. The external linkage is clean and lubed but the arm is not moving a millimeter.
If driving in figure 8s does not help, how much force can one apply to the arm without damaging stuff? A hammer?

 

[VNTS]

How many miles on the Jeep, how many miles on the fluid drained, how often was the t-case serviced per the FSM and when was the last time he attempted to engage 4-LO??

It shouldnt be that difficult.

 

[Jim Allen]

If you can disconnect the linkage and the lever works, then it's internal to the t-case. If you haven't done that, do it before anything else.

Just so you know, this usually comes from not "exercising" the t-case (or occasionally from internal damage).

I had a Blazer years ago (NP-208 part-time t-case) that had this problem. Nothing I did worked and it was definitely in the t-case. I knew I was going to have to tear it down if I couldn't break it loose, so I sprayed some penetrant on the exterior shaft where it enters the case, put a prybar on the shift lever, applied gradually increasing force and... pop... it released. And worked fine thereafter. The PO had never used the 4wd in 96K miles! Had the t-case not released, I was prepared to drop it and tear into it.

 

[PT1]

Once you get it unstuck..(if you can) be sure to tell him to run it in 4lo once every 3 months.

 

[47HO]

Try this. While rolling very slowly forward in Drive, shift the transmission selector to Neutral, and while still rolling, try to move the TC shifter to Neutral.

 

[Gary Allan]

I don't have a clue what your issue is .... but the 247 is what's referred to as a "progressive on demand" transfer case. It uses a Gerotor pump to engage clutches and uses the differential between axle speeds to drive the gerotor pump. Limited differential between axles ..no application of the clutch packs.

That's the figure "8" reference you see. It's to provide excessive differential to free the piston that applies the clutches.

Your problem is with the lock out part of the system.

I can't find an exploded diagram.

 

[Nick R]

Put it in Neutral and then while stopped shift into 4 lo.

 

[lars11]

We had a look at a diagram and it seems that what's stuck is probably the splined "synhcro ring" that moves to lock the output axle either straigt to the HI or to the LO planetary.
The "synchro ring" is connected to the outside lever via a follower. IF I got the diagram rignt...
The gerotor is ok, he tried it on mud and it did lock up all four.