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calebsnowberg
September 2nd, 2010, 10:50
I just purchased a 1987 mj with a 4.0 and aw4. When I got it it had some problems but I thought it just ran rough because of vacuum issues then I thought the tranny might have some problems because it started making a clunking kind of sound but it did not really have any rhime or reasons as to when it does it. Fluid is good and it shift great. This leads me to believe maybe the cat is making the noise. I crawled under it today and it sounds like all of the catalyst inside might be broke. Idk I was wondering if anyone has had any problems like this or any idea where to start.

kastein
September 2nd, 2010, 12:03
on an 87 I think you can unbolt the exhaust system right before the cat, there should be a 4 bolt flange - undo or cut those 4 bolts and take a peek inside, see if the catalyst core is broken and rattling around.

If it is, you can replace it pretty easy, make sure you get an OEM fit one if the flange on yours is rusted too badly, because a universal won't come with the flange. If your flange is OK you can save a decent amount by getting a universal and welding the flange from your old one onto the inlet tube on the new one.

The stock bolts for that flange are M8xsomething but a 5/16" bolt works great, I think I used 5/16" 1.5" long ones but I'm not sure. You'll need to buy a new gasket for the flange but they are like a dollar or two on rockauto.

calebsnowberg
September 2nd, 2010, 13:38
Thanks man, I went out and smacked it with a hammer a few time to see if I could hear it rattle around and I couldn't but now it is like I have a really bad miss so I think that is what it is. At least it's alot cheaper place to start. I'm just going to cut it off because I'm sure the bolts will break and if it fixes I'm just going to weld a pipe in.

Thanks

Johnnie Walker
September 2nd, 2010, 13:44
You can get a replacement magnaflow that bolts on for 100$ or less. Or there are universal cats for like 40$

joe_peters
September 2nd, 2010, 14:43
http://performance-curve.com/410225-225catalyticconverter.aspx

$36.95

CharlesS
September 2nd, 2010, 14:52
I just purchased a 1987 mj with a 4.0 and aw4. When I got it it had some problems but I thought it just ran rough because of vacuum issues then I thought the tranny might have some problems because it started making a clunking kind of sound but it did not really have any rhime or reasons as to when it does it. Fluid is good and it shift great. This leads me to believe maybe the cat is making the noise. I crawled under it today and it sounds like all of the catalyst inside might be broke. Idk I was wondering if anyone has had any problems like this or any idea where to start.

There is an inspection cover at the bottom of the transmission bell housing that allows access to the torque converter and flex plate. There are several bolts that attach the torque converter to the flex plate which are know to loosen up over time.
Remove the cover and check the tightness of these bolts. If they are loose; then remove one at a time and apply blue loctite and IIRC torque the bolts to 28 ft lbs (good and snug if you dont have a torque wrench).

Charles

calebsnowberg
September 2nd, 2010, 15:55
Thanks man I will try that also. And it doesn't really matter I'd I have a cat or not since I'm in kansas and we don't have to do inspections or meet emissions ever year and the CEL wont come on since it so old so I don't see the point of putting one back in do you guys.

joe_peters
September 2nd, 2010, 17:38
Yes, it is FEDERALLY mandated emissions equipment that reduces pollution.

nick86
September 2nd, 2010, 17:42
Thanks man I will try that also. And it doesn't really matter I'd I have a cat or not since I'm in kansas and we don't have to do inspections or meet emissions ever year and the CEL wont come on since it so old so I don't see the point of putting one back in do you guys. Let the flaming begin:flame:

joe_peters
September 2nd, 2010, 18:00
Let the flaming begin:flame:

Well, if you insist...

http://www.youtube.com/watch?v=idTPiHS1g58&feature=fvw