JeepcoMJ Posted September 17, 2007 Share Posted September 17, 2007 what could cause this? 4wd on highway? no lube? bad/bent 4wd linkage causing it to be semi-in gear? this happened to my buddy's (now mine) 95 xj the night before he left for his 15 months tour of the sandbox with his primo-marine pals. something tells me it's bad karma, but I sure hope not. Link to comment Share on other sites More sharing options...
DirtyComanche Posted September 17, 2007 Share Posted September 17, 2007 I've seen that before! But it was different. Involved flat towing and a slight going into gear issue... I'm not sure. But look for bearings that have seized once you get the remains out. Link to comment Share on other sites More sharing options...
JeepcoMJ Posted September 17, 2007 Author Share Posted September 17, 2007 flat towing you say? so was the t-case in your situation in neutral and accidently slipped to 4wd? or was it in 4wd and the tranny accidently slipped into park/another gear? if it's the latter, the tranny may very well be f*d...it could have locked itself up too. Link to comment Share on other sites More sharing options...
DirtyComanche Posted September 17, 2007 Share Posted September 17, 2007 He was flat towing a YJ with the tcase in 4wd and the tranny in neutral. I have no idea why he felt that was the best way to flat tow it... Anyways, it somehow got into gear and carnaged the tcase entirely. It is possible that the tranny locked up due to lubrication issues. I don't recall if he threw out the tranny after that or if it was fuct too (he threw out the entire drivetrain within short order, a 2.5L doesn't do much for a guy who loves speed). Link to comment Share on other sites More sharing options...
Pete M Posted September 17, 2007 Share Posted September 17, 2007 Shifting a 231 into 4wd on pavement can certainly do that. The 231 is not an all-wheel-drive case and should only be used on slick or loose surfaces. Link to comment Share on other sites More sharing options...
87manche Posted September 17, 2007 Share Posted September 17, 2007 is the chain still in one piece? 4Hi at highway speeds can break the chain, and when it snaps around that's what happens to the case. if the chain isn't broken, I'd say it was just a fluke mechanical thing. The perils of driving something that's 10 years old. Link to comment Share on other sites More sharing options...
JeepcoMJ Posted September 17, 2007 Author Share Posted September 17, 2007 the chain is 100% intact and doesn't even look stretched... it seems like the seal was leaking...probably had no fluid in it. Link to comment Share on other sites More sharing options...
FxRacing282 Posted September 17, 2007 Share Posted September 17, 2007 also if the chain is stiff id say there was no oil... Link to comment Share on other sites More sharing options...
TNT Posted September 17, 2007 Share Posted September 17, 2007 I have seen 4 or 5 transfercases break like this and all were caused by running in 4wd part-time on pavement. None of them broke the chain. The case is the weak link when the driveline binds. My vote is it was in 4wd on pavement. Link to comment Share on other sites More sharing options...
DirtyComanche Posted September 17, 2007 Share Posted September 17, 2007 So, if you blow up your tcase on pavement, then why doesn't it explode on the high-traction rock of moab? Link to comment Share on other sites More sharing options...
FxRacing282 Posted September 17, 2007 Share Posted September 17, 2007 good point Link to comment Share on other sites More sharing options...
JeepcoMJ Posted September 18, 2007 Author Share Posted September 18, 2007 lower speed is why it doesn't explode then. Link to comment Share on other sites More sharing options...
FxRacing282 Posted September 18, 2007 Share Posted September 18, 2007 well wouldnt the pressure of hauling 4200lbs up a steep incline be the same pressure? how many axles have you heard of just driving along at 50 and then snap? (this does not include d35) Link to comment Share on other sites More sharing options...
JeepcoMJ Posted September 18, 2007 Author Share Posted September 18, 2007 ...this is a t-case not an axle. what happens is on dry pavement, there is no slip for the tires. the np231 is not a full time case, it's only part time. so it is designed to have some slip. no slip between the front and rear axle, the stress point between them is what brakes...and that point is the t-case. if you're hauling with it, in 4wd, on dry pavement, it may not blow because that extra weight would potentially make at least one tire slip a bit. but there is no reason for 4wd on dry pavement. Link to comment Share on other sites More sharing options...
DirtyComanche Posted September 18, 2007 Share Posted September 18, 2007 I can tell you with reasonable certainty that your tires will always slip enough to take up the difference in wheel speed while moving at a decent pace. To think that your tires always have 100% traction on the road surface is simply wrong. They always slip a little, and the side walls flex to make up for slight inconsistancies in drivetran speed. Not to mention that you do not make sudden changes in relative wheel speed while travelling fast - it simply isn't possible. If you've driven anything with a spooled axle at high speed and really thought about exactly what is going on - you'd understand. And on a related note, the stress is highest is actually when you're going slow and making tight turns. My NP231 logged far more time on the street in 4hi than you'd think. Sure, a fair amount of it was in low traction (slow, ice), but almost always the case was left in 4wd for the entire duration of the winter. Both I did that and the PO (original owner). Once it gets cold enough the roads clear up again and you again have a high traction situation. Why didn't it break? Simple. There's not enough torque load on it from the marginal amount of binding it sees on the street to actually produce a failure. Cases that have failed on the street are most likely already damaged. Bad bearings, stress cracks in the housing, worn chains, etc will often rear their head while seeing the cyclic stresses of being in 4wd on a higher traction medium. But, I'll not disagree that street use will prematurely wear out a tcase. And Jeepco... Extra weight is ALWAYS extra stress. If it causes you to lose traction more than otherwise, the actual torque loading on the parts is still MUCH higher than had it not been in that situation. I know of many other part time tcases that get left in 4hi for the winter. Clear roads or not. Link to comment Share on other sites More sharing options...
JeepcoMJ Posted September 21, 2007 Author Share Posted September 21, 2007 found reason replaced t-case. it's a 23 spline short input t-case. the only thing that blew was the case itself, all the bearings are good, and the internals look like new. BUT the front driveshaft universal intermediate assembly blew the f*k up. so I'm thinking that that's been broke a while. then the wobble (there was wobble...I didn't know what it was) kept going until the case cracked, and fell off. oh, and it was in 4wd as well. the shift fork in there tells me that in fact it was... Link to comment Share on other sites More sharing options...
TNT Posted September 22, 2007 Share Posted September 22, 2007 found reason replaced t-case. it's a 23 spline short input t-case. the only thing that blew was the case itself, all the bearings are good, and the internals look like new. BUT the front driveshaft universal intermediate assembly blew the f*k up. so I'm thinking that that's been broke a while. then the wobble (there was wobble...I didn't know what it was) kept going until the case cracked, and fell off. oh, and it was in 4wd as well. the shift fork in there tells me that in fact it was... My bet is this was the cause "oh, and it was in 4wd as well" and this was after the fact "the front driveshaft universal intermediate assembly blew the f*k up". Link to comment Share on other sites More sharing options...
JeepcoMJ Posted September 22, 2007 Author Share Posted September 22, 2007 yep tim, I think it was in 4wd with a fubar'd front d-shaft and the wobble in the d-shaft (yay non-balanced d-shafts!) caused cracks in the case which destroyed itself... it's an OK theory... pics manana Link to comment Share on other sites More sharing options...
pingpong Posted September 24, 2007 Share Posted September 24, 2007 Transfer case have a bias built into them.. just cause you are in 4wd doesnt mean both axles are seeing the same bias. What it appears to have happened is some kinda of torsional stress.... more then likely cause by fatigue. I think lack of trany fluid or.. popped into gear with too much right foot. Link to comment Share on other sites More sharing options...
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