NP231 no low range (not a shifter issue)

M

mbjeeper

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Joined
Feb 17, 2022
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2
Location
wv
I am putting back together a '97 that I bought a while ago.
Pretty much finished, but I ran into a small problem
I have no low range in the transfer case. 2Hi, 4Hi, and neutral are fine.
It isn't a shifter issue. I shifted it by hand at the transfer case and felt the detent when it went into 4Lo.
I have the front driveshaft off and I can turn the front yoke when the shifter is in neutral. When I put it into 4Lo I cannot turn the front yoke.
I can hear a whirring sound in the transfer case is in 4Lo. It is not grinding, but I can hear mechanical movements.
I can rebuild 18s and 20s, but I haven't yet been into a 231.
I am in a bit of a hurry to get this Jeep on the road, so I will probably just replace this case with a known good one and rebuild this one later, but on the off chance that this might be an easy fix I thought I'd ask what it probably is.
Does this sound like a stripped gear or hub, or maybe a shift fork that is too worn to get it all the way into 4Lo internally?
I'd appreciate your thoughts.
Thanks

Greg in WV
Many '42 to '97 jeeps and Jeeps
 
Hard to tell and if there is any issue you’ll probably have to open it up anyways. 231 is super simple and I’ve had mine apart more than I’d like to admit. Idk how other cases work but going from 2h to 4h moves the fork onto the splines of the chain sprocket that ties the 2 together. 4h then moves it to grab the planetary gears for the reduction. Make sure when you engage 4h you spin the yoke and see both front and rear yokes move together and you’ll probably hear the chain move inside too. That should rule out a chain problem. Also make sure when you’re shifting at the case side and not have the tub lever connected at all. Idk if this was implied when ya said it but sometimes the tub levers can bind and while the lever clicks and detents into 4low, it isn’t actually in 4 low. Then if you know if the lever is fully in the 4 low position and it’s bound up then something is holding it back in the planetary gears.
 
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