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Discussion Starter #1
when I'm at any half-severe angle w/ my Jeep, I get this really wierd and awful sounding grinding noise from under the jeep. I can't tell if its from the front or rear, but I do know that it's not a brake or anything like that. I have a feeling it's a driveshaft. I have never heard anyone else's Jeep do this though. Anyone have any comments on this? It's kind of worrying me. In case it's any help, I have 3 inch lift on it.
 

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Jesse ZJ Some of the front drive shafts need to be longer with a 3" lift. Some are adjustable..I saw one that pulled apart when he jumped the truck. There are aleast two different front shafts. I couldn't figure out what ZJ you have......Don S..
 

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On 2002-03-16 00:43, Jessezj wrote:
when I'm at any half-severe angle w/ my Jeep, ...[snip]...
I don't understand what this means. Off camber? Having the front wheels turned? Heading down a steep slope?
Jay
 

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Discussion Starter #5
It happens when going up or down something at a side angle, like a diagonal position I guess. I've already replaced the front driveshaft one time. I'm not sure what kind was put in the place of it. It has a boot at the end where it goes into the front axle. That's about all I konw. I've looked and can't find where it is coming in contact with anything.
 

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hmmm, I'm still not sure I'm picturing this correctly, but have you checked for signs of rubbing on the rear driveline? The exhaust? How about the body just above the springs?

While you're at it, check the motor mounts, the transmission mount, and the trackbar (front and rear) bushings, and ball joint rod-end.

Jay
 

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Discussion Starter #8
JayH, I remeber now when I broke my front driveshaft last time, the guy that fixed it said I had a broken motor mount and that it probably happened first from all the torque of the motor (since I have it tuned up a little) and then, since it's AWD, it was just a chain reaction and snapped the front driveshaft. I have checked the exhaust. No scarring or anything. I'm gonna go check my motor mounts. I'll let you know if that's what it is.
 

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Discussion Starter #9
K, I just looked under there and both driveshafts are tight, so that's good. I checked the motor mounts and they acted fine. umm.......the only thing I could see is that at the knuckle on the rear driveshaft where it joins and goes into the rear axle, the knuckle has been rubbing against the corner of my flowmaster .40 series. it's not messed up the muffler or anything and hasn't messed up the driveshaft, but it has kinda scraped the metal 'shiney clean' on the knuckle of the driveshaft. Theres only one problem with this simple solution though, now it has started grinding when turning left on a flat surface. but, not at an idle speed. Just kinda excellerating a good bit. and also, when I leave off the line really hard it does it. could this be a broken motor mount causing the shift in the front driveshaft which makes the sound? But how does that tie into going slow over an obstacle as small as a curb at a side angle??? HELP!!!!!
 

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Yup, As you torque the motor, it wants to 'turn' in the engine bay. WHen it does, it takes the entire powertrain (everything up to the pinions on the axles,) and the exhaust along with it. If the motor mounts are shot, they'll allow excessive travel of all those components.

As you traverse an obstacle (curb) at an angle (so that one wheel travels up relative to the other one,) you're flexing the suspension. This time you're moving the body and everything attached to it relative to the drivetrain and exhaust. Again, if the motor mounts are shot, they'll allow the body to travel into the drivetrain/exhaust components.

Have a good mechanic take a look at the mounts, motor and tranmission, to determine if they need replaced. The rubber construction can make it difficult to determine if they've gone bad or not.

GL and keep us posted,
Jay
 

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if you are still having problems after the mounts have been checked/replaced, you may want to inspect the transfer case. you did not say if the noise happens all the time, payment, loose gravel, high range, low range, etc. after 96, i believe the np249 unit had low lock, but yours may not be working properly. the sound you hear, may very well be the TC visous coupling failing or slipping. i started having problems w/ mine also, when placed in a bind, hard acceleration on wet surfaces (spinning only the front tires), etc. hope this was of some help. i do have some information on swapping the 249 for a 242 select-trac. let me know if you have any questions.
 

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Discussion Starter #12
Any way I can check those things myself? I'm at school and don't really know any good mechanics around the area. I've been under it and checked all I could by sight and by attempting to move things with my own two hands. So far everything feels tight and looks like it's in place as it's supposed to be. I drove it a little today and everything seemed fine, but I didn't get on it anywhere or do anything crazy with it. Let me know if you guys have any tricks up your sleeve....
 

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You can check the motor mounts yourself. With the engine running and the trans in Park, Swiftly open the throttle plate by hand causing the engine to jump in RPM's (The idea is to provide as much air to the mixture as quick as you can so the engine revs up quickly.) If the mounts are bad, the motor will jump in the engine bay quite noticeably - This is a relative term I know.

You can check the transmission mount the same way, but you need someone to goose the accelerator while you're underneath watching the mount.

A little movement of the drivetrain is expected seeing as the mounts are rubber, but a bad mount will allow the engine to violently jump within the constraints of the mounts framing.

Jay
 

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Jay H.......Could this be in the t-case..like a chain problem??
""also, it feels like it loses power and doenst' want to go. That's what leads me to believe that it's a driveshaft. Help please!""............I have only worked on the BW QTs....Don S..
 

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Not much would surprise me Don :) I don't see anywhere in this thread what kind of case jesse is using, but the grinding he describes leads me first to suspect some interference from suspension flex.

Maybe there is something else going on as well? Without being there and having a hands-on, it's always tough to know...

Jay
 

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Discussion Starter #17
ok, so far what I've found out is that the motor mounts act fine. When I broke my first driveshaft, which was thanksgiving 2001 (about 4 months ago), I had a broken motor mount also. The guy said it would be best to go ahead and replace the other one too, so I have two brand new motor mounts along with a new driveshaft. It was fine for a while until about 3 weeks ago. I was just driving offroad, not going at it hard at all. I was on the beach and went up a slight step where the waves had made a small lip in the sand and it started grinding going up that. I stopped, put it in reverse and backed down the slope and didn't attempt it again. I have the np249 quadratrac trans. The only thing is now that I noticed today was that if I turn sharp to the left or right, even on a flat paved surface, the grinding starts, even at idle speed. I do not have sway bar disconnects and I still have factory track bars, front and rear, just to add to the info I've already given. If there's anything else I can tell you guys to help me out, let me know. I'm more than willing because I dont' want to take it anywhere unless I konw for sure I can't fix it myself. Thanks guys..
 

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I had a similar problem with my 96 5.2L. It kept knocking and eventually started to do it all the time. I thought it was something with the T-case of drive shafts, but it eneded up being the fuel pump. For some reason it just slowly went bad and even some people from the shop could not tell that was the problem to start with. The pump would still run but was not working.
Another time, I had an even similar problem and I know you're gonna hate to hear this, but I had to have the transmission rebuilt. Luckily the Jeep had about 100 miles left on the warranty and it was covered. I have not had any problems since. I want to put a 3" lift on my Jeep, but I want to make sure my jeep is ready for it before I do, any tips? Good Luck with your problem.
 

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Jesse....Sand?...The sand may have packed or scooped into something like into a front brake area, bending a brake rotor shield. Look for places in the fenderwells, something may have bent and caused tires to rub. Check the bottom of the fan shroud. Something probley got bent and the steering seems to effect it.......Keep trying..Don S
 
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