NP249 will not engage 4hi (infinte grinding); 4lo works amazing - JeepForum.com
 
LinkBack Thread Tools
post #1 of 7 Old 08-07-2013, 03:17 PM Thread Starter
x1n54n3x
Registered User
1998 XJ Cherokee 
 
Join Date: Mar 2011
Location: Mammoth Lakes
Posts: 80
NP249 will not engage 4hi (infinte grinding); 4lo works amazing

I've adjusted the linkage- it is not the linkage. Anyways, I haven't found a thread yet that will describe to me what is happening when a tc gear grinds and will not engage. I'm looking at the blown up diagram in the Haynes manual and still can't determine why 4lo works so well, yet 4hi does not.

sidenote: prior to 4hi becoming impossible to engage and just grinding, it would occasionally pop out while driving. The linkage was loose, so I made sure it was nice and tight before the last time it went out. After that, 4hi popped out and was impossible to engage back.

Can it be that the internal shifting mechanism (not the linkage) has failed and left the 4lo part of it unscathed? Just a thought.

Anyways, if anyone has experience rebuilding the 249 or has had a similar experience and figured it out, please let me know what's going on down there. Thanks!

Edit: Upon closer inspection, I've identified a few parts of the 249 that deal with shifting.

(35) the Shift Sector looks like it has teeth and rocks either clockwise or counter clockwise depending on the gear. Can it be possible that the sides of the teeth that engage 4hi are completely worn? It looks like this can be what's grinding when the gear pops out and if it has dulled teeth, it would make sense that it cannot catch and thus "eternally" grinds unless I shift into 4lo?

x1n54n3x is offline  
Sponsored Links
Advertisement
 
post #2 of 7 Old 08-07-2013, 05:05 PM
Timo_90xj
Web Wheeler
 
Timo_90xj's Avatar
1998 ZJ 
 
Join Date: Mar 2006
Location: Helsinki, Finland - on the European side of the Atlantic
Posts: 7,260
Quote:
Originally Posted by x1n54n3x View Post
Can it be that the internal shifting mechanism (not the linkage) has failed and left the 4lo part of it unscathed? Just a thought.

Anyways, if anyone has experience rebuilding the 249 or has had a similar experience and figured it out, please let me know what's going on down there.
First things first, have you checked that the linkage bushings are good and has not popped out (they are located on both the side of the bracket attached to tranny, and the other side on the unibody center tunnel; on the driver's side). It is very common for them to fail and cause a no-shift on the TC.

If bushings are ok, on the inside of the TC there are only a couple of things that control mode changes; the bezel that gets rotated by the linkage, which in turn moves the mode fork(s) mounted on the shaft (231 and 242 has two forks, 249 only has one). The mode fork(s) move the shift collars on the mainshaft splines making the mode changes (depending on the case there are one or two).

What can fail?

1. Mode fork slide pads. They're made of plastic and wear out or crack over time, especially with misadjusted linkage - even more so if AWD/4hi/4lo pops out under load. I'd say the most common cause.

2. Mode fork(s) fail; fairly uncommon but I've seen a few guys break them.

3. Shift collar(s) fail; it's quite uncommon, but not unheard of. If you grind 'em a lot then yes, things can break.

Mode fork shaft/ retainer/ mode change bezel, I've never heard anyone breaking them. Anything can break for sure, but I doubt those are the reason..

1998 Grand Cherokee 5.9 LX daily driver, 1.75" BB, 32" KM2s, HPD30 Eaton e-locker/D44a stock LSD, 4.56 gears, custom- fabbed tube bumpers and tube fenders,...

http://www.jeepforum.com/forum/f13/d...s-etc-1222317/


1990 XJ Limited (4-door), 4.0 I6, AW4, NP242, ***rolled and totalled @ 165k miles***

***Under construction***
1990 XJ (4-door), 4.0 I6, AW4, NP242, PBR 42" tires, Unimog 404 portal axles, 110" WB, full cage + uniframe completely rebuilt, front 3-link + panhard / double triangulated 4-link rear,... ***SOLD***
Timo_90xj is offline  
post #3 of 7 Old 08-07-2013, 05:48 PM Thread Starter
x1n54n3x
Registered User
1998 XJ Cherokee 
 
Join Date: Mar 2011
Location: Mammoth Lakes
Posts: 80
Thanks Timo for the response.

The bushings: This was my initial issue- I had pulled my trans and swapped in a new one and when it went back in, I think that the linkage wasn't setting up against the bushing fully. It wasn't that the bushing was bad, I had just not fully popped the linkage/bushing back into the TC. This is why I think initially I was having 4hi pop out (as well as trouble engaging 4lo). I did, however, correct this and got the linkage and bushing set properly. Shortly after is when 4hi failed on me though. The timing on this may be coincidence because it shifted into 4lo perfectly right after.

The 249 does not have a mode fork so I guess it may be the Range fork/fork pads on the 249? I'm going to search the interwebs right now to see if anyone carries that part, though I should have my 249 opened by this Friday.

Edit: Range forks are out there, in the sub-$30 range.
x1n54n3x is offline  
post #4 of 7 Old 08-08-2013, 09:15 AM
JohnnyZJ
Registered User
2007 JK Wrangler 
 
Join Date: Oct 2008
Location: Calgary
Posts: 2,571
put 38" tires on it and run it full time in 4 low




if you still have a 93-95 tcase in it swap it for a 231 or 242. that tcase is a POS anyway.....

07' JKUR rollin on 35s
JohnnyZJ is offline  
post #5 of 7 Old 08-08-2013, 09:51 AM Thread Starter
x1n54n3x
Registered User
1998 XJ Cherokee 
 
Join Date: Mar 2011
Location: Mammoth Lakes
Posts: 80
Funny you should say that, I run it unmuffled and for the past week I've been driving to work (<1 mile, 40mph speed limit) in 4lo. It's loud, I need to pull over on occasion so that cars can pass lol.
x1n54n3x is offline  
post #6 of 7 Old 08-08-2013, 10:08 AM
JohnnyZJ
Registered User
2007 JK Wrangler 
 
Join Date: Oct 2008
Location: Calgary
Posts: 2,571
lol! awesome

serious though. the 2wd tcase is so nice. and if this one is acting up (as it sounds like, although seems rare) because after you pull the case apart to see whats wrong, you're already halfway there to swapping inputs on a new tcase

i'd just throw it in the junk bin

07' JKUR rollin on 35s
JohnnyZJ is offline  
post #7 of 7 Old 04-14-2015, 01:49 AM Thread Starter
x1n54n3x
Registered User
1998 XJ Cherokee 
 
Join Date: Mar 2011
Location: Mammoth Lakes
Posts: 80
resurrecting this thread...

I've since picked up a new 249 for the ZJ. I actually have picked up TWO new 249's for the ZJ. Anyways, she runs fine these days after swapping in a donor 249 with about 70k less miles.

Initially a friend around town sold me his np249 for really cheap. I then learned all about input shafts, gear cuts, etc. Later on, I picked up the correct case, proceeded to r&r for the 5th time- success. She works perfect again.

Going through all of my old junk and clearing my shed's workbench today, I came across the first NP249 that lost 4hi and am wondering what I should do with it.

I don't feel like tossing it in the junk bin, that feels like a waste, especially considering the VC wasn't the reason for the swap. I still would like to track down the culprit to losing shifts into 4hi. Like I said, shifting into 4lo worked fine and drivability was great. In fact, during research for this topic was the first time I had ever even heard about the VC going bad and the symptoms that accompany that issue.

My new questions: To the guys who have ventured into his 249- is the mode fork assembly easily accessible? Will it be fairly obvious what is wrong once I crack the case into two- thus allowing me to order the correct replacement part, whether it be a mode fork, or slide pad? Has anyone even ever "fixed" their 249, barring a VC replacement? Any resources? Would this literally just be a waste of time- honest question.

This thing is a giant paper weight at this point and I'm interested in getting it working again. A master rebuild kit is 90 bucks and the mode fork is about 45.

BTW- I have a 95 i6 NP249 (.840" input shaft length, 23 spline input, late gear cut, 16mm input bearing) I'd be willing to get rid of, depending on shipping. It is a fully functional paper weight with about 135k miles on it.
x1n54n3x is offline  
Reply

Tags
np249 , rebuild , transfer case

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the JeepForum.com forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid e-mail address for yourself.



Email Address:
OR

Log-in









Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.




Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page



Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome