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Unread 08-07-2013, 03:17 PM   #1
x1n54n3x
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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?

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Unread 08-07-2013, 05:05 PM   #2
Timo_90xj
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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..
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Unread 08-07-2013, 05:48 PM   #3
x1n54n3x
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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.
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Unread 08-08-2013, 09:15 AM   #4
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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.....
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Unread 08-08-2013, 09:51 AM   #5
x1n54n3x
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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.
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Unread 08-08-2013, 10:08 AM   #6
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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
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