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Rockridge 4WD IS Taking Zone Offroad Suspension Lift Kits BLACK FRIDAY SPECIALS!! You asked, we deliver!Rough Country Lift Kits and Parts!

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Unread 07-29-2013, 10:27 AM   #1
bigchieftaco
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1997 ZJ 
 
Join Date: Jul 2013
Location: Humboldt, Iowa
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Looking at my first Jeep!

Hey guys!! I am looking at buying a 96 ZJ from my brother-in-law. He wants $500 for it. It is a 4.0 4x4 with 167k.
He said it has a parasitic battery drain and makes a knocking noise once warmed up.
I'm not worried about the battery drain yet, I think it might be the cluster.
I've done a ton of reading on the forum already but didn't come across anything like my issue.
I drove it 16 miles to my dads house, it ran fine and drove good. Once I got there I parked it and opened my door to listen for the knocking noise. I didn't hear it until I put it in gear or neutral. Its a probably knocking 2-3 times a second and gets faster with higher revs.

I think its either the flexplate or a rod.
It only does it after it warms up, but not every time. He said he tried to get it to do it for people but it wouldn't sometimes.
I haven't had time to look at it yet and was hoping someone with knowledge could chime in and let me know where to look.

From what I've read, most flexplate issues are on cold starts.

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Unread 07-29-2013, 11:39 AM   #2
Kevinyj95
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Whats the oil pressure at? When warm Or hot. Flexplate or rod would be constant. I would lean more towards low oil pressure. Also the location of the knock/tick would be very helpful. low high end etc. Have you changed the oil what does it have for oil in it? Some people will add a thicker oil to try to conceal a cam bearing issue. Have you tried doing a motor flush? Perhaps a faulty lifter/ lash adjuster.
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Unread 07-29-2013, 11:50 AM   #3
bigchieftaco
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Quote:
Originally Posted by Kevinyj95 View Post
Whats the oil pressure at? When warm Or hot. Flexplate or rod would be constant. I would lean more towards low oil pressure. Also the location of the knock/tick would be very helpful. low high end etc. Have you changed the oil what does it have for oil in it? Some people will add a thicker oil to try to conceal a cam bearing issue. Have you tried doing a motor flush? Perhaps a faulty lifter/ lash adjuster.
IIRC, the oil pressure was normal. I didn't look at the oil myself, but my dad(the mechanic) checked it while we were looking it over and said it looked good. I think he was just checking it had the proper amount.
The only thing we have done was drive it to my dads. We had a family reunion this weekend so we didn't have any time to tinker with it.
In my opinion, it almost sounds like its coming somewhere near the bell housing, which makes me think flexplate.
The whole cold/warm thing throws me through a loop though.
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Unread 07-29-2013, 05:37 PM   #4
zj97ltd
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4.0's aren't that quiet compared to a lot of other engines. They have piston slap from the factory, so if you're not used to one, what you're hearing may be perfectly normal. Maybe try making a video with sound and post it if you can.
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Unread 07-29-2013, 06:17 PM   #5
bigchieftaco
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I'll get a video in a moment. I just checked the tranny fluid after a 10-15 mile drive and it looks pretty low. I'll get some added and going to take the flexplate inspection cover off in a minute and look at it. I'll upload a video in a minute.
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Unread 07-29-2013, 06:30 PM   #6
bigchieftaco
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Here is the video of the knocking. What do you guys think?

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Unread 07-29-2013, 07:28 PM   #7
bigchieftaco
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I think we found the problem.
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Unread 07-29-2013, 10:14 PM   #8
bigchieftaco
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After further inspection, it looks like one of the bolt heads broke off so someone decided to weld where the head was. They also tack welded the other 3 bolts so they don't come loose.
At this point, we are unsure whats causing the knocking sound. Did all that welding throw the balance off and mess stuff up?
If we put the jeep in neutral or gear and feel the transmission oil pan, it vibrates. Once in park, it stops.
To even look at the tranny, we will have to replace the flexplate since they made it damn near impossible to remove. He also thinks it could need a torque converter, rear main seal, and possibly a tranny oil pump.

At this point, dad said he is going to talk to a transmission shop tomorrow and see what they think.
Also, on a side note. The tranny fluid was a whole quart low. Did driving it with low tranny fluid take something out?

Last edited by bigchieftaco; 07-29-2013 at 10:35 PM..
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Unread 07-29-2013, 10:30 PM   #9
Oldfrog
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Just exactly WHO does stuff like that???
Freakin' morons.
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Unread 07-29-2013, 10:38 PM   #10
bigchieftaco
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Yeah, I mean, seriously. Loc-tite and proper torque will do just fine.

I'm definitely not sure I want it at this point. If I could pick the Jeep up for $300, I'd do it. I have up to $600 just in parts if it needs an alternator.
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Unread 07-30-2013, 06:09 AM   #11
zj97ltd
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Makes me wonder what other surprises might be in store with that thing.
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Unread 07-30-2013, 06:41 AM   #12
Kevinyj95
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All jeeps require rear main seals. If it leaks oil its the rear main. There not that difficult since you don't need to remove the engine or tranny and usually cost 10$ and the oil pan gasket. What makes you think the torque converter and pump are bad? no driving it a quart low shouldn't do anything. These surprises are all a part of buying a used car. 500$ isn't that bad. That flexplate is going to be a b****. I would check a jy for a transmission that way you get the torque converter and pump and any other surprises with that out of the way. Take the alt off and get it bench tested. I keep looking at that pic and thinking why?
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Unread 07-30-2013, 08:14 AM   #13
bigchieftaco
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Quote:
Originally Posted by Kevinyj95 View Post
All jeeps require rear main seals. If it leaks oil its the rear main. There not that difficult since you don't need to remove the engine or tranny and usually cost 10$ and the oil pan gasket. What makes you think the torque converter and pump are bad? no driving it a quart low shouldn't do anything. These surprises are all a part of buying a used car. 500$ isn't that bad. That flexplate is going to be a b****. I would check a jy for a transmission that way you get the torque converter and pump and any other surprises with that out of the way. Take the alt off and get it bench tested. I keep looking at that pic and thinking why?
It's leaking oil, and we think its from the rear main. I didn't know they were that easy to install, thanks for the tip!
I'm not sure the torque converter and pump are bad, just kind of the worse case scenario. They might have messed the threads up on the TC by welding on the flexplate.

When we first took the inspection cover off, the flexplate was much hotter than both oil pans and exhaust. Is that from the low tranny oil or should it be that hot?
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Unread 07-30-2013, 09:01 AM   #14
Kevinyj95
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The tranny fluid shouldn't have anything to do with the temp of the flexplate. But yes it will get hot. Whats the transmission fluid look like? If its nice and red/pink you should be okay. Smell it aswell if it burns your nose and smells burnt you have an issue. May not be a bad Idea to drop the pan and take a look. there is a magnet in the bottom of the pan that collects metal particles so they don't get sucked back up. Look for large clutch pieces or metal. note its normal to find glitter type metal in there stuck to the magnet. That will tell you a lot about the tranny and what condition the converter should be in. Big chunks of metal and crap = big trouble. The pan fluid in the pan is 5 Quarts not the entire 13 Quarts of the transmission. Theres also a filter you can change if you have the money comes with the gasket. If the pump is bad your fluid should be burnt and most likely brown or clear. Thread repair isn't too bad. Its what damage caused the need to weld. I am surprised a I6 had the torque to do that. Maybe the bolts were stripped so they did that? That's beyond me. That's some shady tree mechanic stuff right there.
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Unread 07-30-2013, 11:19 AM   #15
bigchieftaco
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Quote:
Originally Posted by Kevinyj95 View Post
The tranny fluid shouldn't have anything to do with the temp of the flexplate. But yes it will get hot. Whats the transmission fluid look like? If its nice and red/pink you should be okay. Smell it aswell if it burns your nose and smells burnt you have an issue. May not be a bad Idea to drop the pan and take a look. there is a magnet in the bottom of the pan that collects metal particles so they don't get sucked back up. Look for large clutch pieces or metal. note its normal to find glitter type metal in there stuck to the magnet. That will tell you a lot about the tranny and what condition the converter should be in. Big chunks of metal and crap = big trouble. The pan fluid in the pan is 5 Quarts not the entire 13 Quarts of the transmission. Theres also a filter you can change if you have the money comes with the gasket. If the pump is bad your fluid should be burnt and most likely brown or clear. Thread repair isn't too bad. Its what damage caused the need to weld. I am surprised a I6 had the torque to do that. Maybe the bolts were stripped so they did that? That's beyond me. That's some shady tree mechanic stuff right there.
Yeah, I checked the quality of the oil and it was a nice reddish/pink color and didn't smell burnt.
It drives fine and has good power but after the 15ish miles of driving it starts making that ticking/knocking sound.
It might just be the flex plate, period.

I know my situation is pretty damn unique, but has anyone else ever had this knocking sound after driving 10-15 miles?
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