NP242 Chain?

OK...trying not to be long, but I think I've narrowed it down to the chain.

At my clubs event, I broke a rear drive shaft at the differential u-joint. Occured when starting from a stop in a twisted situation...front going up, rear doing down...wedged into the ditch. Twisted the ear right off and busted the tab on the diff yoke. Repaired with a spare ds and doner pinon yoke. After, had vibes that seemed less when in full-time 4-wheel.

Decided it was time for a build. Built and installed a Ford 8.8 rear axle with 4:56 gears and Ected limited slip/locker. Also built front axle with E-Locker with 4:56 gears. Also did Tom Woods SYE and rear CV driveshaft. After all the build, still have vibes.

To chase the vibes down, I removed rear drive shaft. With vehicle in 2wd in garage, can hear a "tick-tick-tick" that seems to be about the right timing for the t-case chain. With rear ds removed, vibes present on highway, worse upon decel, not so bad on accel, almost non-existent at "neutral" coast (not on, or off the gas).

Check rear output shaft...turns without any wobble (not bent)...good because it is a new shaft with the TW SYE kit.

Have had front DS rebuilt...rebuilt CV joint and U-joint, and balanced by a good driveshaft shop. Haven't checked front output shaft for wobble (yet).

Since hearing the "tick-tick-tick"...I'm thinking the chain got "stretched" when rear DS busted (all the torque transfered to front at the time of the break and taco'ed the chain).

I need to fix as it's my daily driver. Also...might not be related, but I've noticed that transfer case gets hot now...can't hold a hand on it after 10 miles of highway driving. Is this normal? Is heat related to chain?

I'm ready to buy new chain and do the install, but wondering if I'm on the right track. Anybody else ever experienced the same/similar issue? I love my 242 and don't want to go to 231...just want a highway-ready wheeler that can wheel the tough trails when required.

Thanks in advance for the help.

Hallo. Once my T-case was very hot.. It was staying in the locked position 4 wd. (disengage problems) :shhh:

'92 XJ

Mmm, I could see how that might heat up a 231 case, but I've run my 242 in 4-high for quite a while before...usually in the winter, and don't remember it getting hot.

Thanks for your thoughts! Anyone else got any thoughts on the issue?

Did you do a hack and tap? I didn't think there was an SYE kit available for the 242?

I did a Tom Woods SYE. He might have "hacked-n-tapped" it, but I didn't. I did check the rear output shaft for trueness...rotates without wobble. Still wondering if chain got damaged when rear DS blew on me (stretched a joint or two so it's uneven?)

I don't see how a stretched chain would cause a vibration. It would make noise though if it was stretched enough to rub the case.

Not sure about the temperature of the case either.

I'm thinking the stretch is only over a link or two...caused when the rear DS snapped under load, shifting all the engine torque to the front via the chain. If only a couple of links stretched, the rest would ride the shaft gears nicely, and the stretched section would ride roughly. I'm thinking the frequency of that "rough riding" portion of chain could set up a vibration, and that the increased friction could create the heat. Is my thinking off-base?

I have no idea. The maximum torque rating for the NV242 is 1486 lb-ft.

Is it possible for the chain to stretch from torque alone (versus age) from the 4.0? I don't know.

Bump

OK...so not so much help here on this one. I'm going out on a limb, and based on my "expertise", I'm thinking chain. I ordered one from NAPA today...$96. It will be in mid-week next week. I'll get it in after the 4th and will let you folks know if it solves my vibe problem or not. Either way, I figure, a chain with 270K needs replacement anyway, right?

I will post a follow-up.

Not a bad idea to replace the chain, but I doubt that is the issue. When my chain was stretched, I couldn't tell at all in 2wd, no matter what the situation. Certainly no vibes from it. But in 4wd, the front axle felt like it was being hit with a sledgehammer as the chain skipped teeth.

Ben

OK...bumping this one. A little long..but please bear with me, want to give all the relevant information.

Got my new chain and putting it in this weekend. I decided to do some front/rear testing before tearing the t-case apart.

I put rear on Jack stands and ran up to 60-65 mph in 2WD. Had minor vibes at about same frequency as my primary complaint. Then removed rear driveshaft and put front on jack stands. Again ran up to 60-65 mph (in part-time 4WD, so front would spin). Same vibes, only more noticable...more pronounced...but on same frequency. In both cases, heard a faint "tick-tick-tick" in time with chain rotation from t-case...bad link?

While rear output was turning, I laid a straight edge against rear output flange...no wobble. Did the same to front DS near output shaft, again no wobble...so assuming front and rear t-case output shafts are not bent (rear is new SYE...so only really suspected front might be bad to begin with).

So, since vibes occur with both front and rear drive only, source is t-case (right?). and since front only produces worse vibes, I'm suspecting chain since in rear only, chain just rides (no tension), and when front only, chain is driving front.

So, I split the case and remove chain and front & rear output shafts. I inspect the chain...can't see anything obvious. I wiggle every link...all feel the same, so no obvious problem.

Things I do notice. Rear output shaft moves a little back and forth is 'gear pack'...but wouldn't the rear bushing tighten it up when rear flange is installed/tightened? Chain sprockets have wear marks from chain, but all are even (none worse than others). No significant metal particles collected on magnet. Front output bearing and rear output bearing have no "play"...appear good without shadowing or scoring. T-case fluid (new about 1,000 miles ago since SYE) appears good...smells same as new-in-bottle fluid.

So, gonna put new chain in tomorrow and button back up and hope vibes go away. Anyone got any ideas before I button it back up? What about front axle u-joints...they're original x260's or ???...want to upgrade to x297's, but haven't yet. Could a bad front u-joint be causing the vibes? (doubt it since felt with rear running at speed with front standing still...but willing to consider all possibilities).

As always...thanks in advance!:sure:

Any solution to this one?!?
I had a very similar issue.

MJ/I6/AX-15/231

Lost the rear universal, drove a bit in 4wd with the rear drive shaft removed. Replaced the uni and had no issues in 2wd. It rained pretty hard the other day and i popped it into 4wd. I got out of rain and switched into 2wd. heard a large klunk. Then the Tick-tick-tick started. I thought at first that it was the vac disco not releasing. The ticking was much quieter in 4wd. Long story short... I pulled out of Home Depot tonight and the drive train seemed to slip. I limped home (it was only a 1/4 mi.) riding the clutch and going 15mph. I will crack the T-case very soon... wouldn't mind an update beforehand...

Thanks!

Well, not good news from my end. Got the new chain, replaced the old chain (it looked as good as the new one)...no difference! I'm baffled...thinking maybe front axle u-joints...but haven't taken the time yet to investigate.

Mine didn't make really nasty noises...and the tick-tick-tick was only audible if you ran in gear with rear jacked up...and head under the unit. Never had any slipping problems...just vibes that come and go...bad at 30-35 mph...and again at highway speed (60-70 mph). turn a corner...sometimes disappears...sometimes worse on accel...sometimes worse on decel. Go figure!!!

Well, I will post what I've got so far in case it helps anyone...

i got the t-case out and split it open. The fluid did not have the burnt smell and was not discolored, but there was significant grey metal mucus in around the magnet. Fun. the oil pump filter mesh was melted with a hole in it. There were plastic pieces (tiny) everywhere from the mode selector pads. They were new 5K ago. The mode forks show a little wearing. The bearings spin free and tight. The seals are not dried out. The chain DOES seem to be stretched, but not too bad?

i think the pump clogged, failed, and the fluid just sloshed around.

My solution is to get a 231C, take the pump, planetaries, and primary gears for the Mjs 231. A new chain is on the way from Napa.

Here is hoping.