Weird 4x4 issue

Buck_nekid · Friday at 5:36 PM

I have an 02 limited, 3.7, NP231. The issue is that it will not go into 4x4 unless I come to a complete stop and put the transmission into reverse. It doesn't have to move in reverse just the little bump you would get in any vehicle by shifting it into gear. I know what caused it. I let my buddy borrow it and my driveway is semi-steep. He said he started spinning (knowing him he was wide open) and slipped it into 4x4. I bet he had the front tires going 0 mph and the rears going hard to tell how many mph. Has anyone had the NP231 apart and can think of what happened inside of it? The shifter linkage is good. I've tried every possible combination of shifting the transmission and transfer case, it definitely needs its input shaft turned in reverse to engage 4X4. Thoughts of what to look for when I drop it and split the case?

lfhoward · Friday at 5:40 PM

Buck_nekid said:
I have an 02 limited, 3.7, NP231. The issue is that it will not go into 4x4 unless I come to a complete stop and put the transmission into reverse. It doesn't have to move in reverse just the little bump you would get in any vehicle by shifting it into gear. I know what caused it. I let my buddy borrow it and my driveway is semi-steep. He said he started spinning (knowing him he was wide open) and slipped it into 4x4. I bet he had the front tires going 0 mph and the rears going hard to tell how many mph. Has anyone had the NP231 apart and can think of what happened inside of it? The shifter linkage is good. I've tried every possible combination of shifting the transmission and transfer case, it definitely needs its input shaft turned in reverse to engage 4X4. Thoughts of what to look for when I drop it and split the case?

This is a strange one. I wish I could help you out, but I haven't heard of this happening before. I bet it will be easier to fix your manually shifted NP231 than the electronically shifted TC on the later models.

Welcome to the forum! What part of WV are you from? Dolly Sods Wilderness and the Canaan Valley are some of my favorite places to camp & wheel.

Buck_nekid · Friday at 5:59 PM

lfhoward said:
This is a strange one. I wish I could help you out, but I haven't heard of this happening before. I bet it will be easier to fix your manually shifted NP231 than the electronically shifted TC on the later models.

Welcome to the forum! What part of WV are you from? Dolly Sods Wilderness and the Canaan Valley are some of my favorite places to camp & wheel.

Yes I've tried to explain the issue to a few people and they say "it doesn't work that way," until I take them for a ride then it's "Humm, weird" I guess I'm got my weekend all planned out.

I am up north in Wellsburg (in between Weirton and Wheeling) in Brooke County.

JeepJeepster · Friday at 9:22 PM

Im assuming its not always been like this?

Ive found that all tcases will shift better if you are rolling 2-3mph in N. They normally always pop right in.

Its tough to get them to shift when youre stopped.

Buck_nekid · Saturday at 7:10 PM

JeepJeepster said:
Im assuming its not always been like this?

Ive found that all tcases will shift better if you are rolling 2-3mph in N. They normally always pop right in.

Its tough to get them to shift when youre stopped.

No it only started when my buddy did the rear wheels spinning with the fronts standing still thing. I've tried to get it into 4x4 from 0 MPH to 70 MPH. Rolling in neutral in both directions. The only way I can get it in 4x4 is to shift the transmission into reverse. The transfer case needs the input shaft turned in reverse for it to go into 4x4. I can put it in 4x4 and drive all day and it remains in 2wd, the second I go to reverse it is then in 4x4. I've gone over exploded diagrams and it's a pretty simple case, there is 3 "synchronizers." I assume they are "yellow metal" and he tore them up. I'll know when I get some free time.

JeepJeepster · 2025-03-02T10:15:46-0500

I wasnt aware that they had sycro's. Im seeing that early 231's did, but Im not sure if these do.

Im not sure why they would need sycro's. Everything should be spinning at the same speed, given youre not doing what your friend did.

Buck_nekid · 2025-03-02T12:56:54-0500

JeepJeepster said:
I wasnt aware that they had sycro's. Im seeing that early 231's did, but Im not sure if these do.

Im not sure why they would need sycro's. Everything should be spinning at the same speed, given youre not doing what your friend did.

I will know shortly. I'll update the thread with my findings. They are calling #23 and #24 syncro's. Hopefully that is all that's tore up.

-ash- · 2025-03-03T10:39:34-0500

Buck_nekid said:
No it only started when my buddy did the rear wheels spinning with the fronts standing still thing. I've tried to get it into 4x4 from 0 MPH to 70 MPH. Rolling in neutral in both directions. The only way I can get it in 4x4 is to shift the transmission into reverse. The transfer case needs the input shaft turned in reverse for it to go into 4x4. I can put it in 4x4 and drive all day and it remains in 2wd, the second I go to reverse it is then in 4x4. I've gone over exploded diagrams and it's a pretty simple case, there is 3 "synchronizers." I assume they are "yellow metal" and he tore them up. I'll know when I get some free time.

Sounds like the end of the shaft splines that slide to engage the gears have been bent. Like a bent axle spline. Wont go in unless you match the splines up by shifting into reverse to reverse "like a screw" to start it onto the shaft.
Id find whole transfer case on a wrecked one for 100$. or shift into 4x4 with reverse, like you are doing.

Weird 4x4 issue

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