NP 231 Test?
- Thread starter saburai
- Start date
XXXpedition
Explorer
i don't know about a standard test, but when my SYE kit was installed, they put the seal in wrong. i lost all the fluid. on my way from LA to vegas it emptied out completely.
without oil i was still able to go in 4 low.
it melted the shift fork and the chain was a bit loose. got that fixed, seal put in properly, refilled it with fluid and went another 150k miles...
total about 250k miles and a tough live
never serviced it!
without oil i was still able to go in 4 low.
it melted the shift fork and the chain was a bit loose. got that fixed, seal put in properly, refilled it with fluid and went another 150k miles...
total about 250k miles and a tough live
never serviced it!
saburai
Explorer
Thanks for the reply!
The reason I ask is that I picked up a used 231 with a SYE already installed. The PO seemed like a good guy and he said it was in good working order.
None the less, I would like to "go through it" to the best of my ability before I install it.
I'm a pretty fair mechanic but I'm a green horn to the XJ platform and four wheel drive systems as well. The 231 that's in my truck works well but occasionally when I first engage low range, it will "pop out" of gear and it sounds like the chain is just spinning. How difficult is the NP231 to work on? Are special tools needed?
Many thanks...
The reason I ask is that I picked up a used 231 with a SYE already installed. The PO seemed like a good guy and he said it was in good working order.
None the less, I would like to "go through it" to the best of my ability before I install it.
I'm a pretty fair mechanic but I'm a green horn to the XJ platform and four wheel drive systems as well. The 231 that's in my truck works well but occasionally when I first engage low range, it will "pop out" of gear and it sounds like the chain is just spinning. How difficult is the NP231 to work on? Are special tools needed?
Many thanks...
alosix
Expedition Leader
The 'pop out of gear' issue tends to be more with shift linkage adjustment than inside the t-case. The linkage is 1/2 mounted to the body and 1/2 mounted to the drivetrain, if you start working the Jeep some its pretty easy to get it to pop out of gear if its out of adjustment.
So, I'd check over the adjustment, make sure it firmly goes into 4lo when you put it back together. Other options are the Novak shifter kit that bolts directly to the t-case/transmission. Its a good bit of work to install (need to custom bend the shift rod for your vehicle) but once its in it provides a very positive shift for the 231. I've never had this pop out of place on my TJ (the road going one) or our comp TJ (the flip over a few times a weekend one).
I'd run through each of the shift positions spinning it by hand looking for any rough spots in rotation or tight spots, but if you took it apart to do an SYE you would have seen damage if it was there, the 231s are pretty simple, not much room for anything bad to hide.
alosix
Expedition Leader
Ah, I just don't have enough coffee in me this morning
.Besides making sure it will shift into each of the gears/ranges and turning smooth there's not much you can do until you get it into the vehicle (at least the skids on an XJ are that hard to deal with
). Unless the chain is brand new, there will be some slop in it, and shifting tends to take a little rotation of the input shaft to get it into gear.If you're really worried, grab a tube of rtv and tear it apart to inspect it. You'll likely need an impact to get the yokes off on the bench though.
231s will take a beating though. The only one I've dealt with that had a chain problem was our comp YJ. Running 36" iroks and beating on it for 2-3 seasons finally broke a few links in the chain. It was still in one piece, but was getting a little noisy. It also destroyed a few of the bearings at one point, you could tell that by some side to side movement of the output shaft. I really wasn't ably to diagnose that one from the outside though. It needed a good teardown to find everything that had been beaten up on it.
Jason
ExpoMike
Well-known member
Dextron III ATF fluid, same as the AW4 transmission.
As Jason said, there is not much testing off vehicle you can do outside of a general inspection. If you can spin everything without binding and it shifts between ranges, you're most likely okay. Overall these are solid cases, outside of the case itself. They are light weight aluminum cases and don't like to be hit by rocks or binding from driveshaft problems.
There are a couple upgrades that can be done, since it's share with a few other vehicles. The planetary gear assembly can be swapped with a 6 gear version (stock is 3) and a wide chain kit can be done. I actually have both of these parts and will do the swap later this year.
Oh, before draining the fluid, make sure you can get the fill plug out first. Some have done it the other way and found problems getting the fill plug out after draining. Then they can't refill it.
BlueBomber
Adventurer
this goes for changing ANY fluid!!! it has happened on more than a few transmissions ive worked on.:victory:
Root Moose
Expedition Leader
I'll nod in agreement with the above.
The only other thing that can go wonky with these cases is if the little plasticy things on the shift forks/collars get worn or come apart or similar. Very rare but i've had the luck of having it happen to me (actaully a BW case but they are the same at his level). In that situation you can have symptoms like you describe that is not related to the shifter mechanism.
Really simple case, crack it open while you have it out of the vehicle. No more complicated than a manual transmission, in fact arguably simpler since no reverse lock out mechanism.
Fun afternoon look see. You know, with all that free time you have.
The only other thing that can go wonky with these cases is if the little plasticy things on the shift forks/collars get worn or come apart or similar. Very rare but i've had the luck of having it happen to me (actaully a BW case but they are the same at his level). In that situation you can have symptoms like you describe that is not related to the shifter mechanism.
Really simple case, crack it open while you have it out of the vehicle. No more complicated than a manual transmission, in fact arguably simpler since no reverse lock out mechanism.
Fun afternoon look see. You know, with all that free time you have.
Root Moose
Expedition Leader
Maybe I'm more dense than usual this afternoon... I'm not understanding what you guys are saying.
Huh?
What does order of operations have to do with getting the plug out? The thing is threaded: I put a wrench to it - it's coming out.
???
ExpoMike
Well-known member
Some people have had problems getting out fill or drain plugs, either seized in the housing or not having the right tool (some fill and drain plugs are different and take different tools).
The idea is, make sure you can get new fluid in BEFORE you take the old fluid out. If not, you're not going anywhere at that point. :elkgrin:
Root Moose
Expedition Leader
Ok, I guess that is a point...
... I thought there was some mysterious mechanical impediment you guys were getting at...Plug is coming out on my terms...
ExpoMike
Well-known member
Yes... but the real question is... will it go back in? :victory: