NP231 Shifting in the MJ

[88mjblue]

I have an 88 mj with the np231 t case and ba 10/5. Coming from two previous jeeps with the np231 (99TJ, 95 XJ) I always have been able to shift on the fly into 4hi, but with my new mj I can't do this - I need to come to a complete stop in order to shift into 4hi. Is this normal?

[MuddFoot]

no

[88mjblue]

no

That's what I thought. But when I do shift to 4Hi, it works fine, so does 4Lo. I also need to come to a stop to shift out of 4Lo (can't do the rolling 2-3mph change)

[xjrev10]

I guess I always stop with the vehicle in neutral to go to 4lo...

[88mjblue]

I guess I always stop with the vehicle in neutral to go to 4lo...

 

Yeah I do that too sometimes, either way is fine for 4Lo, but it's the 4Hi that I should not have to stop for.

[Eagle]

4-Hi is supposed to be shift-on-the-fly up to 50 MPH.

[Incommando]

A long shot but you may have a motor and/or tranny mount issue. The shift linkage design on these is pretty poor. When under power the drivetrain could be shifting enough to prevent the linkage from moving the range lever correctly.

[4cyltoy]

I'm going with the Novak cable when I do my 4wd swap. Might want to look into it if you use 4wd often

[cruiser54]

Are you depressing the clutch or no? You shouldn't be.

 

Can be shifted at "any legal speed" per the owner's manual. 

[88mjblue]

A long shot but you may have a motor and/or tranny mount issue. The shift linkage design on these is pretty poor. When under power the drivetrain could be shifting enough to prevent the linkage from moving the range lever correctly.

 

I'm not sure about that because I let off the accelerator and put in neutral just to be safe. Like I said, I've driven several NP231's for years and never had this problem - I have noticed in the past that the T case usually doesn't like shifting on the fly when under too much power like climbing a hill, so I have always gotten in the habit of shifting not under load.

 

 

 

I'm going with the Novak cable when I do my 4wd swap. Might want to look into it if you use 4wd often

 

I think you might be on to something with the cable...  I checked out the Novak cable here: http://www.novak-adapt.com/catalog/shifters/sk2xc.htm

But it's ~$150 so I think I'll try to look into adjusting my existing shifting mechanism because something must be wrong here. But I like what they're talking about, I always felt the shifting was clunky on these jeep t-cases.

 

 

Thanks guys, I really wanted to confirm firstly that there wasn't an older version of the NP231 with a different shifting mechanism. 

[88mjblue]

I had a specialist look at it, they said the problem was that the syncros in the t-case are worn out. He said it will be an expensive repair and would involve essentially rebuilding the transfer case. Other than that, nothing else is wrong with it.

So, for the meantime, I will be stopping to shift into 4wd.

 

Just for kicks, what makes a transfer case go bad? Excessive shifting? Too much sharp turning?

[88mjblue]

It's actually not a big deal right now in the winter here in colorado, lots of roads are all snow packed, so I've been in 4 hi for the most part. The only problem now is when the snow starts to melt, that's when I like being able to shift in and out depending on the road conditions and what's been plowed.

 

[Eagle]

 

A long shot but you may have a motor and/or tranny mount issue. The shift linkage design on these is pretty poor. When under power the drivetrain could be shifting enough to prevent the linkage from moving the range lever correctly.

 

I'm not sure about that because I let off the accelerator and put in neutral just to be safe. Like I said, I've driven several NP231's for years and never had this problem - I have noticed in the past that the T case usually doesn't like shifting on the fly when under too much power like climbing a hill, so I have always gotten in the habit of shifting not under load.

 

 

DON'T put it in neutral. For shift on the fly you should be in gear, at "neutral throttle" -- which doesn't mean in neutral, it means balancing the throttle so you're not accelerating and you're also not coasting or compression braking. That keeps everything rotating at the same speed while you shift.

[cruiser54]

 

 

A long shot but you may have a motor and/or tranny mount issue. The shift linkage design on these is pretty poor. When under power the drivetrain could be shifting enough to prevent the linkage from moving the range lever correctly.

 

I'm not sure about that because I let off the accelerator and put in neutral just to be safe. Like I said, I've driven several NP231's for years and never had this problem - I have noticed in the past that the T case usually doesn't like shifting on the fly when under too much power like climbing a hill, so I have always gotten in the habit of shifting not under load.

 

 

DON'T put it in neutral. For shift on the fly you should be in gear, at "neutral throttle" -- which doesn't mean in neutral, it means balancing the throttle so you're not accelerating and you're also not coasting or compression braking. That keeps everything rotating at the same speed while you shift.

 

YES!

[Rockfrog]

I had a specialist look at it, they said the problem was that the syncros in the t-case are worn out. He said it will be an expensive repair and would involve essentially rebuilding the transfer case. Other than that, nothing else is wrong with it.

So, for the meantime, I will be stopping to shift into 4wd.

 

Just for kicks, what makes a transfer case go bad? Excessive shifting? Too much sharp turning?

This is something you can literally do yourself.

The brass and steel synchro assembly was actually eliminated sometime early in the 90's (not sure when - maybe with the gear pitch change in 94?) And just a plain steel single piece was used.

The cheapest solution is to swap another tcase in for around 50 bucks and a bit of time to swap the input gear across. Easy to do.

Or just run it like it is.