Transfer case bangs, sounds like it's going to explode

My '91 NP-242 transfercase feels like it's going to explode when it's in full-time operation. I was on the highway, on snow covered roads, driving straight, and every three seconds I would feel and hear a bang, just as if I hit a pothole. In part time, it does it but not as violently. Could it mean my shifter forks are bad? It also hops around tight corners in full time, like say at a parking lot. I would like full time as the canadian winters are harsh, but I don't want anything to blow up on me. Anyone had this problem?

I'm guessing it's the shift forks or the center diff. What does it sound like to you guys?

ya kind of the same mine had a pin come loose and it took links off the chain and almost cut the case in half!!! mine would bang and pop. I would drain the fluid and look for metalic sparkles or shavings

I took it apart a year ago (it has less than 5000 km's on it since I put it in, although it has 250,000 total since I got it from a junkyard) and took this pic:



I couldn't make the chain skip by hand and it wasn't super loose. It boggles my mind what it could be because it seemed fine when I took it apart. I did notice all the pitting on the case, is that normal? All those red dots on the case, you can tell they are bumps when you run your finger over them.

if you look in your pic the pin holding a gear has fallen and is hitting the chain its by the shift fork in your pic. if you look at the chain you can see where the pin hit the chain

ceb0217 said:

if you look in your pic the pin holding a gear has fallen and is hitting the chain its by the shift fork in your pic. if you look at the chain you can see where the pin hit the chain

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Edit: Hmm I'm not really seeing what you're seeing. Care to draw a circle on it and the chain?

ya mabe I cant rember exactly but thats what came loose on mine .a little weld broke and it ate the washer/spacer .that might not be what happend to yours but id look at it.you will have to turn the gears/chain to look at the others and compair

I had intermittent problems with my 1990 NP242 which sound identical to yours, although it wasn't consistent..sometimes 4wd would work flawlessly and other times I would get the same bang/losing power to the front wheels that you describe (in both full time and 4hi/4lo). I had originally suspected that the chain had stretched, but since it was only doing it once and a while I decided that the problem might be related to a shift fork or something else and not the chain since it didn't seem to matter if I was under load or just coasting down a gravel road.

Anyhow, one day it was acting up, popping out of 4hi and banging away so I gave it a ridiculously hard flogging and with one final 'bang!' it seemed to have fixed itself somehow, I havn't had any major problems since. Once in a blue moon I'll shift into part time/full time and feel that it hasn't entirely 'engaged' so I just shift back into 2wd and try again, usually the second time does the trick and I'm happily on my way. To be honest I think I had this problem since I bought the jeep a few years ago so I don't attribute it to any other damage happening. I just completed an 800km trip halfway across the province in full-time the entire way because the highway conditions were so iffy and I had no problems with it at all.

I'm not too sure what I'm getting at here, I mean..I don't really want to recommend that you flog your Jeep too hard, but I find a little 'tough love' has fixed all kindsa problems with mine over time. If I were you I would start by checking the fluid level, next I would try adjusting the TC linkage and if that doesn't fix it, start looking at the shift forks or chain next.
Good luck and let us know what you find, I'm interested to hear what the problem is just in case mine starts acting up again!

sorry it took so long Im not really good on the computer and it farted so i had to restart it

Basics of the NP242:
All four tires have to be the same brand/model/size, at the same pressure and wear. If they aren't, don't even go farther trying to diagnose problems with noise and difficulty shifting.

Jim www.yuccaman.com

Yucca-Man said:

Basics of the NP242:
All four tires have to be the same brand/model/size, at the same pressure and wear. If they aren't, don't even go farther trying to diagnose problems with noise and difficulty shifting.

Jim www.yuccaman.com

Click to expand...

I've had this problem with two different sets of tires. The ones im running now are brand new.. I don't think it's that simple.

I also don't think that that pin is missing, I think it's like that on purpose but I can't be sure as I don't have any other pictures of an NP242 case to compare.

Major update.

I drove around in full time 4x4 all around city and the backroads, and I was climbing a very steep hill in 2nd gear, lots of torque, and the bangs got louder and louder and finally at the top of the hill I got a collosaul BANG followed by grinding sounds and no power.

I took it home in part-time as it didnt grind but the bangs in part time got tremendously worse. Finally at home, I put it in full time and let the clutch out when all I heard was a whirring sound and grinding. No movement to any wheel whatsoever. Part time and 4-low still worked.

Here's my theory:
My front Dana-30 was originally a vacuum disconnect, however in prep for the NP242 swap, I took out the vacuum lines and put washers to move the shift fork over permenently. Perhaps what is happening is for some reason the shift fork is letting go under different torque loads which frees up the front half the transfer case, and drive shaft. This is why I'm getting bangs in part time. The reason I'm getting worse bangs in full-time would be attributed to the fact that when the front axle 'disconnects', I lose all power since all the transfercase power is now shifted to the front end.

The grinding sound I heard is exactly like the grinding sound I got when my front disconnect was malfunctioning earlier.

However, when I got a camera and set it up under the jeep to see if the front driveshaft was spinning when I heard the grinding sound, it wouldn't do it anymore.

Does this make sense to all of you? Clunk, I noticed you had a 1990 XJ. Do you have a vacuum disconnect D30 by any chance?

Super major awesome-happy update

(Cross posting from another forum)

I believe I have fixed my NP242 'bucking/banging' problem in 4x4. As I've said before, when in 4x4 and especially full-time, I would get a BANG now and then and one time it got so bad that I heard a BANG and then nothing but grinding sounds. I knew it wasn't popping out of gear because the lever never moved, and the 4x4 light's never changed or went out.

The problem? My front vacuum disconnect. During the time I swapped the NP242 in, I moved the shift fork over with washers and nuts to permenently engage the two-piece axle shaft. I suppose it was either grabbing or shifting enough under different torque loads to cause it to free up and case the bang and grinding sounds.

I spent the last few days tearing apart my front end and replacing the whole two-piece design with a simple one-piece shaft from the junkyard (off an '89 with an NP242 no less) and took it for a spin today. The results? Beautiful, beautiful full-time 4x4 with no more horrible banging sounds underneath. I drove for an hour and not ONCE did I get any odd noises. I took it up multiple hills, revved the crap out of it, cruised, etc, and couldn't get it to bang once. Problem hopefully solved!

TLDR: Front vacuum disconnect must have been screwing up. Replaced with single-piece shaft and all is well!

Winter is fun again!

Congrats on your fix. Glad I have a NON-disco axle. thanks for the update