Help with driveline "BANG" issue

[Jim]

Howdy folks, I'm looking for some input and guestimations...

[1990 Jeep YJ with NP231 transfer case, driver's side front driveshaft, that has a TeraLow 4-Low kit with SYE]

For some time (a year) I've been encountering an occasional BANG from the jeep. It feels solid, substantial, and from under the center of the vehicle. It's something that has been happening more often and is on my list before the season gets into full swing. Aside from the noise and sudden jolt, everything operates normally.

The first time I noticed it was on dry pavement at about 50MPH (forgot to disengage 4WD when jumping from Bunce to Rock Creek). It had two loud BANG's in quick succession. I attributed it mainly to my mistake of being in 4WD on dry pavement... until it would occasionally happen while out on a trail.

In my mind I kept thinking "it must be the chain jumping a tooth" and a few days back Jay (jaymoto) came up and we pulled the case and opened it up. It looked clean and fresh inside (plus, there were no leaks from the case / not cracked). I anticipated copious marks on the inside of the case from a slack, rubbing chain, but no. The case was 98% clean with only a scant mark from the chain and a scant mark on the engagement fork from chain rub.

Christopher (Fordboy77) PM'd a time or two and came with a comment that he encountered an oddity with a front U-Joint. It felt good but upon dis-assembly had wrecked bearings. While I've not removed the front driveshaft U-Joints or axle U-Joints, I do believe I have one on the driveshaft, near the xfer case, that is at issue as the cap is wiped clean/shines under the snap ring so the cap must be moving.

Any thoughts on what could be causing a substantial (sound and feel) bang from under the center of the vehicle? How tight does a chain need to be to be in "good" condition?

I ordered an xfer case refurb kit with chain and bearings (though existing bearings feel perfect) and will replace U-Joints up front too (rears were tended late last summer). Should the chain be my first suspect? Could any other part be at issue? What thoughts say ye?

Thx,
Jim

[Robert B]

i would love to help but sadly would have to be in the vehicle when it happens to try and get a hint of where to look and the exact feewl of it ............so im no help minus rip it all apart and check everything

[Java]

my guess would be ujoint bind, I'd start by pulling the front shaft and replacing all the joints; keep whatever is good, then you'll have some spares to carry. In my experience transfercases are too simple to do intermittent stuff. The np231 chains can stretch, but it takes a lot to get them there and when they do you often will hear it dragging on the inside of the case. it has to stretch a LOT to jump a tooth with the OEM gears, IDK if the 4-1 changes that. I think you would have noticed a loose chain right away when you opened it.

[Robert B]

nah the 4-1 is only the planetary gears in the front half chain is the same ...so are the chain gears

[glacierpaul]

Jim, I have the same year YJ, and last year the carrier inside of the the front diff. came unbolted, trashing the diff. Have you opened the diff's just to look? I also had Bill make me an upgraded shaft and got the upgraded u-joints as well, better than the oem stuff. I plan on the SYE at some point when I do a rear locker.

[Jim]

Have you opened the diff's just to look?

Not yet but a fluid change is in order before this season - so it'll happen asap. Thx for the info.

[carpenle]

I talked to the guy that I get my XJ parts from, he stated that he has never had a bad 231 but has had a bad 242. Not sure that this really helps, but I would say U joints.

[ColoJeeper]

Do you have a locker in the rear axle, and is what you are hearing the locker unloading after it has bound up some? Detroit lockers are notorious for this.

[carpenle]

I know Jim has ARB Air lockers.

[ColoJeeper]

How about the simple things like motor mounts, transmission mounts and t-case mounts? Is there any movement in the drive line when you rev the engine?

[scout man]

When I trashed my spider gears I had something similar (although much more frequent). I lost several teeth an all the spider gear components, and every couple rotations they would meet tooth-to-tooth and there would be a violent bang that could be felt throught the rig as it jumped into the next tooth gap. Now, mine we real trashed and it happened every rotation or so, but if you just broke one or two teeth, its possible that this only happens occasionally, but would likely keep getting worse. I would crack open your diff and just make sure there isnt any metal floating around, and take a quick look at all the teeth, and makle sure things are still tight in there.

[Jim]

Levi's correct - ARB's front and rear. I have NO issues, ever, in 2WD so I'm to believe the driveline for the rear (which includes motor mounts, tranny, xfer case in 2wd mode, rear u-joints, rear diff, etc.) are OK

It only happens when the front driveline is engaged. I can run in 4WD mode (xfer case) but disengage one (typically driver's side) wheel lockout and it does not happen (there's essentially no strain on the front drivetrain). No clue if it happens with front diff locked or not (I don't roll with it locked for long - no need).

I'll open the front diff cover (maybe today) to get a look inside. I do hope the front ARB doesn't need replacement.

[Rick]

It only happens when the front driveline is engaged.axle u joints???

Not ruling them out - but the bang is typical on straight line ops where the axle u-joints aren't overly stressed - they're on the table (plus I should replace seals up there too).

[Jim]

I pulled the front diff's cover and found metal bits laying inside. The ring gear did show a couple damaged teeth. The ARB has "pins" at the case exterior and one of the pin ends looks bad - just like my rear ARB looked when it was toast internally.

I could see putting an open diff into the front axle for the season and saving / doing an ARB again over next winter.

I'll probably call the local 4x4 shop and see their thoughts re cost for open diff reinsert / rebuild with thoughts to doing ARB next winter vs. doing ARB now and suck up the cost now.

[Chris]

Sorry to see this Jim, I say pick up a used open and toss it in the front for the Moab run. :thumb:

[jaymoto]

I second that!

[Rob]

I say pick up a used open and toss it in the front for the Moab run.

I second that. You surely don't need a front locker on the trails we'll run in Moab. Unless, of course, Chris really, really wants to do Kane Creek. Then it could come in handy to get over the big steps on the shelf and drag everyone else over. :)

[Hypoid]

I'll probably call the local 4x4 shop and see their thoughts re cost for open diff reinsert / rebuild with thoughts to doing ARB next winter vs. doing ARB now and suck up the cost now.If you repair what you have now, you'll avoid setting up the gears...twice.

[Jim]

If you repair what you have now, you'll avoid setting up the gears...twice.

You know it! And - it's a job I'd hire out as it's one I do not have experience in.

When I purchased the Jeep, the rear ARB was toast and the cost was $1500 (1K for the ARB + ring & pinion/bearings/seals + labor). That isn't what I have in financial plans for the beginning of the summer.

So, I might just go rear wheel drive only for the summer (remove front driveshaft and never lock in the front hubs and the internals won't spin). It depends upon cost for sticking in an open vs. just holding off to "do it right and do it once". Now, I could just stick in an open and call it good and decide if I want to go ARB up front or not.

Here are some carnage pix. The major item is that ALL of the ARB "hold together" bolts have loosened and come out of what they should be holding together. This makes me wonder if the person WHO PUT IT TOGETHER (before I purchased the Jeep) did a POOR JOB TORQUING THE BOLTS such that they didn't stay. I won't know but that could be the failure mode.

With the angled markings on the outer ARB body I'd like to see the condition of the pinion gear & nut holding it on.

Looking at the bright side of life - working on the driveline will get me well in tune with the condition of the vehicle.

http://www.jimwilliamson.net/automobile/frontrange4x4-pix/2013-03-22-front-diff/Img_1319.jpg

http://www.jimwilliamson.net/automobile/frontrange4x4-pix/2013-03-22-front-diff/Img_1314.jpg

http://www.jimwilliamson.net/automobile/frontrange4x4-pix/2013-03-22-front-diff/Img_1315.jpg

http://www.jimwilliamson.net/automobile/frontrange4x4-pix/2013-03-22-front-diff/Img_1316.jpg

http://www.jimwilliamson.net/automobile/frontrange4x4-pix/2013-03-22-front-diff/Img_1317.jpg


Some sort of ring or seal, broken pieces and below, three remaining ARB hold together bolts (plus some chunk of metal)

http://www.jimwilliamson.net/automobile/frontrange4x4-pix/2013-03-22-front-diff/Img_1322.jpg

http://www.jimwilliamson.net/automobile/frontrange4x4-pix/2013-03-22-front-diff/Img_1328.jpg

http://www.jimwilliamson.net/automobile/frontrange4x4-pix/2013-03-22-front-diff/Img_1323.jpg

http://www.jimwilliamson.net/automobile/frontrange4x4-pix/2013-03-22-front-diff/Img_1324.jpg

http://www.jimwilliamson.net/automobile/frontrange4x4-pix/2013-03-22-front-diff/Img_1326.jpg

http://www.jimwilliamson.net/automobile/frontrange4x4-pix/2013-03-22-front-diff/Img_1327.jpg

[tonkatoy]

Good to hear you found the problem. just sucks it is not a easy fix

[scout man]

yea, I definitely think you found your problem alright! I would be interested to see what caused those scratches on the side of the carrier.

[Geno]

I have some input for you on air lockers. Currently I have ARBs in my Jeep F&R, and I had ARBS f&R in my old 73 Bronco, Dana 44s F&R, and I diagnosed Petes 2000 Taco rear axle ARB issue.I have been running ARBs since 1989. The marks on the case side are from the pinion ,YES, but to fix that, a experienced ARB installer would know to machine down the leading edge on the pinion gear, mainly on Dana 30 and 35 axles to create the clearence, this is the fix from ARB on the early units, the area you machine/grind off is not a ring gear contact area. call your local shop that does ARBs that you have faith in, to check my info. We had to do this on WW2AVG ( forum name )1991 jeep wrangler that we just installed a ARB into his rear Dana 35 C clip axle in February of 2013. It is recommened by ARB to only engage the ARB unit at full air pressure (90 psi in system) and at stop or less than 1 mph. So the the axle engagement gear can slide over to full engagement position before load is applied. I have never seen a ARB with such catastrophic failure, so I am assuming that this unit was engaged under load and/or wheel spin conditions more than once. So when you go to redo axles, find a shop you can trust to do it correct, Open , ARB, Detriot what ever, I pull the axles out and I have a master tech bench install my ARBs, and I have never had install issues yet, but I am in the springs. If I can be of further help send me a note.

[glacierpaul]

Glad I mentoned my front diff prob Jim! My carnage was way worse because I plow with mine and there are always noises from the plow and the set-up, so I totally destroyed the whole diff. I only figured it out when the front tires were not spinning. My mech. said whomever did a regear must have not tightened the carrier bolts to spec, at least that was his opinion.
Good luck with the fix!

[xaza]

What gearing are you running Jim? Do you have the high pinion 30?

[Java]

Sorry to see that, Jim. Hope it's not too much$$$!! Looks like GlacierPaul wins for best web mechanic. :thumb:

[Java]

http://denver.craigslist.org/pts/3589347104.html

if you can reuse your ring gear you can put this in yourself, it's actually really easy to swap just the carrier w/o setting up gears.

[glacierpaul]

Sorry to see that, Jim. Hope it's not too much$$$!! Looks like GlacierPaul wins for best web mechanic. :thumb:

Always glad to help out with diagnostics from the chair:lmao: I have had just about every broke down vehicle scenerio there is, one of the drawbacks to owning a fleet:rolleyes:

[Adaa60]

im Also having an issue like this as well i think, but ive only heard it two times, once below 10mph making a left hand corner in to a parking lot and the other directly after taking off from a stop sign. both times i was in 2wd and seriously felt like it was coming from the rear end. is it something to worry about? ive only felt/heard it two times

[scout man]

Yes!! Open up the rear and take a look at it. Happening twice means there is something in there causing a problem, but it probably isnt too bad yet. Open it up, look for broken teeth, metal pieces floating around, etc. There is probably something wrong, but if its just one tooth broken or something you can possibly still run it (depending on how it broke), but you have to get those broken pieces out of there or it will cause more problems. Usually these problems start small, and then the broken pieces get wedged in bad spots and do significantly more damage.

[Adaa60]

ok then, i will get new fluids and check them both out sometime this week then.

[Rick]

is it something to worry about?YES!!!!!! its not normal for clunking sounds,like Steve said, take it apart now before it really starts to cost you $$$$$$$ kinda like brakes,you hear it make noise Check it.

[Hypoid]

im Also having an issue like this as well i think, but ive only heard it two times, once below 10mph making a left hand corner in to a parking lot and the other directly after taking off from a stop sign. both times i was in 2wd and seriously felt like it was coming from the rear end. is it something to worry about? ive only felt/heard it two timesHave this guy look it over: http://axleandgear.com/

From what I've heard about him, he won't try and sell you someting you don't need.

Every time I see an XJ with an 8.8 conversion, I hold my breath and hope it was not done by SFF Customs... :frown:

[Java]

I can't remember what your gear ratio is, but if it's 4:56 this guy has an entire axle:

http://www.colorado4x4.org/vbb/showthread.php?204228-Yj-parts

[Jim]

I'm 4:10.

Too early to tell what I'll do. Perhaps in a couple days I'll have a plan and folks could kick me for sale / used items if they see'm around.

Thx,
Jim

[carpenle]

Jim,

I have a dana 30 that I was going to use for my 73 CJ5 but did not. Not sure of the gearing or if it would work on your 7, but if you want we can dig into it futher.

[Java]

that makes it really easy- every 4 cyl YJ has stock 4:10 gears, it's a bolt in swap. That's how I regeared my YJ's front, it's easy and you get spare parts as a bonus. I saw one on CL recently for $75.00. HTH