FullOutPwr

I did a search, but didn't quite get an answer I was needing an unfortunately not a genious with TC's. With the assistance of a friend, we installed a SYE on my NP231. Everything went smooth, but we had to break it apart a second time when it wouldn't shift out of 2H on the bench. Got that fixed and it shifted fine on the bench.

Installed the TC into my XJ, and thought everything went fine. Started it up, put it into drive and didn't hear the usual RPM drop going into drive. Hit the gas, didn't do anything and grinded going into park. Thought maybe the lever was in neutral, but it wasn't it was all the way clockwise which would be 2H. Tried it in 4H to see if any change, and it immediately started thumping and actually twisted my new driveshaft just shifting out of park into reverse.

Looking at threads, it seemed like there could be an issue if the SYE was not installed with the case in 4 lo, and I dont recall us doing that. Would this cause these types of issues? What is the necessity of being in 4 lo?

Lead Foot

Having the case in 4 low just makes it easier to get ther gear selector fork back in the slot when assembling.

What did you find wrong with the case after your first shifting issue on the bench? Forget to put the spring back on the range fork shaft? Did you change anything else?

Was your front driveline also hooked up during the "testing"? Just trying to figure out why your rear driveline twisted.

Kris Froehlich

FullOutPwr

I should have mentioned I do not have the linkage currently hooked up, I'm manually shifting it using a pry bar on the t-case range selector. It was shifted manually on the bench, and went through each gear just fine the second time around. We couldn't find what happened the first time regarding the shifting, but tore down and checked it and it started shifting just fine after we pulled the shift fork out to measure it and make sure it wasn't too long. The spring is definitely still on, nothing else was changed besides the SYE.

Lead Foot

Well something was changed between it not shifting on the bench, then shifting after reassembly. How did you twist your driveline though? Did you start reving it up again when you tested it out the second time? Then the t case popped in and out of gear, grabbing once really quick and engaging at a high RPM?

FullOutPwr

I did not rev it the second time, just tried shifting to reverse when the car shuddered and then "clank clank" and found the driveshaft laying on the ground. Front driveshaft was not put in.

It actually just sat in the back of my jeep for a week after install and that's all. I'm perplexed as you. Gonna take it out tear it apart and see if there is a local jeeper to take a look at it who's more knowledgable.

Lead Foot

Yea. Take some pictures as you tear it apart and post them up.

FullOutPwr

Got it out finally. Will have some more pictures of tear down. It only has 2 gears now using the selector.

DieselD

Sub'd

Please share your findings. I would like to avoid whatever you did when I install mine.

Good luck and sorry I don't have any insight.

NewJerseyXJ609

X2!

sreeb

I'm not sure you are looking in the right place.

Absent some kind of snatching or grabbing in the TC which shock loaded the drive shaft, a drive shaft failure is likely caused by something down stream of the TC.

1) I assume you also installed a new drive shaft. Could it have been bad?

2) Rear end locked some how?

3) Emergency on?

4) Tires chocked?

If the drive shaft was in good condition, it shouldn't fail absent you giving it a lot of gas and then only if something prevented the car from moving.

FullOutPwr

Well now I'm really confused. I pulled both yokes off, started tear down and found on a whim now it'll shift through all the positions 2h, 4h, n and 4l where it wouldn't before after.

Lead Foot

I thought you said you already got it into gear and thats when the driveline twisted? Maybe it was just never all the way seated in gear.

When you are shifting the t case from under the rig is it in neutral like it is supposed to be? Sometimes you also might have to roll the jeep back and forth a little to get the synchros to line up. Actual 231 instructions say you should shift into 4lo while at a slow roll and in neutral. Maybe you should pick up one of those fancy FST shift linkages so that you can shift the t case nicely from in the cab.

Aljay

HMMM ive been doing it wrong I come to a complete stop to engage 4 low ?

1998xjspt

so which direction should i push it in order for it to be in 4lo??

salad

4Low has the lever all the way down, 2High is up at the top.

OP, to shift the NP231 you need a small amount of movement to get everything to engage. 4L should be done at a slight crawl, 4H at any speed. Trying to do either at a dead stop can sometimes not work if the teeth arent lined up