Popping in and out of 4HI, troubleshooting help please

[TACTICALJEEP]

1991 XJ, 220k miles.

This problem is driving me nuts, and has for several years now. When driving in 4hi, 25mph+, it will make a loud bang noise, steering wheel shakes one time, then goes away. Very intermittent and can't be forced to duplicate. Doesn't matter if I'm going straight or turning. Feels like it's popping out of 4wd then immediately going back in on its own.

The diagnosis is even more frustrating cause it only happens in the deep sand on the beach, or when driving in the snow. I'm roughly 2 hours from the beach, and until this year, we rarely get snow here in eastern NC. I was hoping it would break and stay broke...but that hasn't happened yet. Once, many years ago on Oakacroke island, it went out and stayed out. Back end was buried on the beach, front tires sitting on top of the sand. As I was winching and giving it throttle, all the sudden "BANG" and it climbed out of the hole (I guess it finally sent power to the front axle).

Seeing how I'm already committed to the Cape Lookout trip in march, and will be driving many, many miles on the beach, I need to get this resolved.

Thinking it maybe something in the front axle (disconnect style HP Dana 30), I've torn it completely down and reinstalled with new carrier bearing, pinion bearings, inspected front locker (it's fine, adjusted correctly), installed new bushings on intermediate shaft and installed posilocker to eliminate the vacuum disconnect motor. However, I never really thought it could be in the front axle, cause when the event happens, I have no power to the driver's front wheel (anything with the disconnect motor etc is all on the right side of the differential)

I've adjusted the transfer case linkage per FSM, it required maybe a 1/16 of an inch, not a lot IMHO because of the amount of play inherent in the OE linkage.

I've pulled the back of the transfer case off and inspected gears, chain, chain guides and tensioners, all looked ok.

I'm leaning towards the following theory:

The chain is stretched. As I'm driving, the chain goes to flopping around and in turn, misses a tooth on either the front or rear output shaft. I feel like it doesn't do it in 4low or under 25mph because there's so much tension on it. (kind of like a bicycle chain with slack at the bottom).

That being said, my master tech jeep buddies I've consulted with disagree. They state that if the chain was stretched that bad, it would do it more often in 4low because there's so much stress on it...

opinions? I'm leaning towards the 225-250.00$ NP231 master rebuild kit with wide chain conversion from JB conversions. I don't want to just throw parts at it, but I'm grasping for straws here. beside, the only way to check for a stretched chain is to lay it beside another right?

 

[1stDeuce]

Have you checked the teeth on both sides of the front axle disconnect collar? If it was only partially engaged when you powered up at some point, you may have damaged the teeth on the axle shaft, or the collar, which will prevent it from engaging all the way now, and it'll pop when you send it power. (Pull the cover and make sure the collar can slide all the way to the engaged position.) Unless you like the disconnect, you might consider swapping it out for an axle that doesn't have it, or converting to a 1 pc axle shaft.

If you pull the t-case apart, a stretched chain will be pretty obvious because it will "bend" the wrong way a lot. Unless you've run it WAY low on fluid at some point, it's unlikely that the chain is "stretched". (Actually, you can't stretch the chain, but the pin holes wear elongated, which lengthens the chain, and will make it jump and pop when you load it. That's why it'll show a lot of sag when you hold it straight out...)

Wait, front locker?? Is it an EZ locker?? They can pop and bang at strange times under power, even when driving straight down the road... ??

Not finding problems with the axle or locker, it's probably time to pull the t-case apart and see what you see... A bad chain will normally jump at any speed just needs load, so you might want to check the shift collar that engages 4wd for damage.

Good luck!

 

[TACTICALJEEP]

Have you checked the teeth on both sides of the front axle disconnect collar? If it was only partially engaged when you powered up at some point, you may have damaged the teeth on the axle shaft, or the collar, which will prevent it from engaging all the way now, and it'll pop when you send it power. (Pull the cover and make sure the collar can slide all the way to the engaged position.) Unless you like the disconnect, you might consider swapping it out for an axle that doesn't have it, or converting to a 1 pc axle shaft.

If you pull the t-case apart, a stretched chain will be pretty obvious because it will "bend" the wrong way a lot. Unless you've run it WAY low on fluid at some point, it's unlikely that the chain is "stretched". (Actually, you can't stretch the chain, but the pin holes wear elongated, which lengthens the chain, and will make it jump and pop when you load it. That's why it'll show a lot of sag when you hold it straight out...)

Wait, front locker?? Is it an EZ locker?? They can pop and bang at strange times under power, even when driving straight down the road... ??

Not finding problems with the axle or locker, it's probably time to pull the t-case apart and see what you see... A bad chain will normally jump at any speed just needs load, so you might want to check the shift collar that engages 4wd for damage.

Good luck!

Thanks Deuce for your reply

The collar is ok, teeth are fine on the intermediate and outer stub shaft. I like having the disconnect for several reasons, most of which, I feel the two shafts are stronger than just one long shaft. (I've broken many a front u-joint but never a shaft, whereas my buddies always break the right side long shaft ) but that's another heated topic for another post.

The front locker is a lunchbox style, and this problem existed before I installed it.

I'm OCD about my maintenance, the case has never been low on fluid, and the fluid gets changed once a year.

I don't understand how you can determine if the chain is stretched once the case is apart. the case halves support the front and rear output shafts, once the case half is detached, the shafts pull into one another because of the chain tension. yea, if it's really really sloppy you'll be able to notice...but I'm sure if it was that sloppy I'd have other issues up to/including a hole worn in the case by the chain.

thanks again

 

[sassy gopher]

Sounds like the linkage is not putting it fully into 4hi I have had this issue on several jeeps. Usually it's 4lo. The factory linkage is not so great in stock location move things around or have it get bent slightly and it will not work right. I gave up on constantly messing with linkage and went with a Novak cable shifter. I have since had no issues at all even with the body lift motor mount lift and tummy tuck

 

[TACTICALJEEP]

Sounds like the linkage is not putting it fully into 4hi I have had this issue on several jeeps. Usually it's 4lo. The factory linkage is not so great in stock location move things around or have it get bent slightly and it will not work right. I gave up on constantly messing with linkage and went with a Novak cable shifter. I have since had no issues at all even with the body lift motor mount lift and tummy tuck

I've adjusted the linkage per FSM, no help. I've had the same event happen to me as well, the difference is when the linkage is out of adjustment, you have difficulty shifting in and out of 4wd, and when it pops out, it stays out. My issue is it's popping out and immediately going back in with in a 1/16 of a second. Just to go a step further, I've adjusted the linkage a 1/4" fore and aft with no change in the symptoms on subsequent test drives. Then to go even further, I've tried driving and either pushing or pulling on the 4wd lever to see if there's a "sweet spot" that prevents the condition from happening...no change at all

 

[Jim K in PA]

Check motor and transmission/tcase mounts. If they allow too much drive train movement, it may be shifting the t-case for you.

 

[TACTICALJEEP]

good brainstorming Jim! But I've already replaced both motor mounts and transfer case mount as well as new cross member (mine was mangled due to getting highcentered too many times). This problem was present before and after swapping out the mounts.

Again, this issue has been present for 6-7years. I just never really bothered with it. All of my recreational wheeling has been rock crawling (4low) and the local recovery calls I respond to for winch outs are on muddy pathd, fields, powerlines, even people's backyards...all of which I use 4low. I never have a need for 4high unless its in the snow or on the beach.

 

[sassy gopher]

You can disconnect the linkage and manually put it in 4wd. It really sound like it's riding just on the edge of where it needs to be. Worst case you spent 15 min and I'm wrong best case you spent 15 min and solved a 7 year problem

 

[TACTICALJEEP]

You can disconnect the linkage and manually put it in 4wd. It really sound like it's riding just on the edge of where it needs to be. Worst case you spent 15 min and I'm wrong best case you spent 15 min and solved a 7 year problem

this is something I haven't done!

now if it'll just snow again so I can test it! :smiley_drive:

it's so frustrating cause I can put it in 4hi and drive as long as I want and it'll never happen unless I'm on a slippery surface ie: snow or sand

 

[1stDeuce]

This is intersting... There's no reason that I can think of that it would skip occasionally in 4 hi but not in 4 low... The front axle disconnect doesn't know the difference, nor does the locker. The t-case uses two seperate shifters for hi-low and 24w/4wd. So if it's the t-case, it should skip in either high or low, since that doesn't affect the chain or the 2wd/4wd shift collar.

I'd fall back on there being a shifter linkage issue, and in 4-hi, you're right on the edge of being engaged, while in 4-low, you're well past that point. They're shifted by a cam pushing on the shift fork inside the t-case, and 4-hi is where the ramp first starts that engages the 4wd shift fork... If you're a little short on travel, you might get some skipping...

Interestingly enough, my 242 was doing something similar, where every once in a while in 4-low in moab it would skip and bang. I pulled it out and put a rubicon t-case in, but I haven't gotten to tearing down the 242. I know it has issues, as the rear fixed yoke output has some play in and out of the tailhousing, and it really shouldn't... Hmm. If you have a bearing going out, or a c-clip out of place, that could allow the output shaft to slide rearward, and that would disengage 4wd some... But again, it should do that in low too...

You'll have to take the chain out to see if it's stretched, but I don't think that's your problem. When I wasted one in my XJ due to a blown rear output seal, it would skip all the time when you put load on it. If your 'case is fine in 4-low, I'd look at the shift linkage really well...

 

[TACTICALJEEP]

I found a local spot with a lot of deep sand. I'm going to try Gopher's recommendation and shift the tcase to 4hi with the linkage removed. And Duece, I'm going to pay extra special attention to the linkage as well. I've examined it so closely though, I still think the problem is internal. if it still acts up with the linkage removed, I'm going to tear it down, and really scrutinize #47 in the above schematic. If it's worn or beveled, I believe it'll give the exact same symptoms.

Thanks everyone and I'll report back sometime over the weekend with my findings

 

[jscusmcvet]

This may not be it, but worth checking out. Pull your console and see if, with your modifications, the 4wd engagement lever is free to move where it needs to in order to fully engage. There is a gold in color metal piece that guides the lever, has kind of a "z" shaped slot that holds the lever in position at each station. In my last rubicon, when I put a small tummy tuck on, I had to use a dremel to remove some material from that piece, to let the lever move fully into position. the symptoms before I did that sound similar to yours, so worth a shot, cause it will only take a short bit to see and no $ to fix if that is the issue.

John

 

[TACTICALJEEP]

ok guys and gals, wanted to bring this one back from the dead because I finally figured it out! I completely disengaged the shift lever and manually put the tcase in 4 hi as a previous poster had suggested, symptoms still there. after going through the transfercase, all was well. reinstalled, condition was still present. I then deleted the cable activated disconnect on the passenger side and put it in a permanently locked condition. symptoms were still there. I then removed the locker, reinstalled spider and side gears....still doing it. So I began tearing it down again cause I was about to set the jeep on fire due to the frustration....and that's when I found it.

you would have thought as many times as I pulled the carrier out I should have noticed there was no preload at all...when I would take the bearing caps off the carrier, it would just fall out on the floor if I didn't catch it. I reached around and grabed the pinion and it had a tremendous amount of play in the bearings (never really paid it any attention before cause it wasn't leaking, incredible pinion seal!). then I noticed the pattern on the ring gear...jeeez....

the combined play in all four bearings (carrier and pinion) was allowing the pinion to actually come away from the ring gear and miss a tooth or two! crazy I know!

I inspected the gear set...and they were kinda chiped and pitted one the edges from the above condition, but once I got it shimmed and preload set, I ck'd the mesh with gear marking paste, and the affected areas were no longer "meshing" and/or contacting anymore.

I'm not beating myself up that bad cause I've never seen anything like this before. but at the same time...lesson learned. When you disassemble something for inspection, it's just as important to note how parts come out...not just the condition of the parts themselves....

as always, thanks to everyone to helped me on this thread, and hopefully the next person searching Google will find it and save them some effort.

 

[1stDeuce]

Good gawd, wasn't it blowing lube all over from the pinon seal?? Glad you figured it out though!!
Chris

 

[TACTICALJEEP]

that's the crazy thing deuce, I never suspected bearings cause the pinon seal was dry...like desert dry! and it didn't have much play with the carrier and ring gear installed...so I never suspected it!