AMC 360 Flex Plate

CJ-22 · 01-01-2007, 06:46 PM

I posted a similar question a long time ago, but I am still having problems. I have a 78 CJ-7 with an AMC 360. It has always had a very slight vibration. I have tried to fix the vibration in the past with no luck. A while back the Flex Plate cracked and I had to replace it. I ordered a new 360 Flex Plate from NAPA auto and swapped them. I discovered that the Flex Plate that was in it was from a 304 and I know this was not correct. I thought I finally figured out my vibration problem, however, when I changed to the 360 Flex Plate, the vibration got much worse. Does anyone have any ideas why this might be? I am not a good mechanic by any means, but everything I read tells me I am supposed to have the 360 Flex Plate, but the 304 Flex Plate works so much better.

Thanks for any help.

**BESRK** · 01-01-2007, 10:55 PM

Wonder if someone didn't swap a 304 Harmonic Balancer onto the motor at the same time as the flex plate? Not sure how to tell the difference or if it's even possible but I would certainly check...

**BLS33** · 01-02-2007, 01:19 AM

Quote:

Originally Posted by BESRK

Wonder if someone didn't swap a 304 Harmonic Balancer onto the motor at the same time as the flex plate? Not sure how to tell the difference or if it's even possible but I would certainly check...

Are you saying when it had the 304 balanced flexplate in there someone may have put a 304 harmonic balancer on as well and now that he's put a 360 balanced plate the harmonic balancer could be causing the vibration?

Because thats something that I would think could cause it.

**BESRK** · 01-02-2007, 08:20 AM

Yeah.. each size AMC engine should come with its own harmonic balancer/flywheel balanced for that engine. I believe though, that the parts will physically interchange so a 304 balancer could be bolted onto a 360. Now, if that 304 balancer were bolted on the same time a 304 flexplate were bolted on, it may not vibrate too bad.. (I don't know... just guessing). Then, when you swapped the correct 360 flexplate on, the difference in balance made it vibrate more. I would try to find the part number for the balancer and see if it's for a 304.. or maybe try to visually compare it to a balancer from a 360 to see if there's any major difference.

CJ-22 · 01-02-2007, 01:55 PM

That is a good idea BESRK. I assumed it had a 360 harmonic balancer all along. I'm going to check on it this week to know for sure.

Hopefully this will solve my problem and hopefully finding a 360 harmonic balancer will not be too difficult.

CJ-22 · 01-02-2007, 08:42 PM

I have now located the part number to my harmonic balancer. It is 3230130. Does anyone know how to tell if this is to a 304 or 360? I have called numerous auto parts stores and checked all over the internet. I still do not know. Any help is appreciated.

CJ-22 · 01-03-2007, 09:36 PM

Bump.

How do you tell which balancer it is? I have found three different balancers online for 360's (none of the part #'s match) and I have found two different balancers for the 304 (none of the part #'s match). I don't want to change it unless I know it is wrong. Anyone know of a website that helps match jeep part #'s?

**BESRK** · 01-04-2007, 06:45 AM

Were you able to get the part number without taking the balancer or pulley off? If so, I may be able to climb around my 360 later on and look.. or even take pics of it to see if it looks the same (no big difference in counterweight...etc.).

If you haven't found the info by the weekend, I'll try to dig around in my shed.. I think I have a 360 balancer in there somewhere.

CJ-22 · 01-04-2007, 03:01 PM

Yes, you can get the number without pulling the flex plate. I had to turn the engine over a couple of times to get the number to the bottom so I could see it. I would really appreciate the help. I have called several places, but these flex plates are no longer available (except from aftermarket dealers, but the numbers are different).

Thanks for the help.

CJ Chet · 01-04-2007, 05:34 PM

Check your local Dodge dealer. You'd be suprised what is still available. That's where I got the flex plate and bolts for my 258 to TF999!

John N · 01-04-2007, 07:39 PM

I got this # off of '72 core I have. Some of the balancing holes were drilled right through the number, so it might not be right.....3196525.

CJ-22 · 01-05-2007, 06:29 PM

Okay, I finally found out what I have. My balancer is definitely a 360 balancer, but this puts me back with the same problem. Does anyone know why a 304 flex plate might vibrate considerably less than a 360 flex plate? I'm not an engine expert by any means, so excuse me if this is a dumb question, but could the engine have been rebuilt incorrectly to cause this? Could an internal 304 part been used instead of a 360 part?.

CJ-22 · 01-06-2007, 07:21 PM

Any 360 experts with advice? I don't know what to do next.

Should I assume the vibration is not related to the 304 flex plate?

**BESRK** · 01-06-2007, 08:58 PM

The tranny to engine bolts are tight right? I've had them loosen and cause vibes before.. I'm running out of ideas.

CJ-22 · 01-06-2007, 09:08 PM

Yes they are tight. I have changed the flex plate several times from 304 to 360 to test it and I had the vibration each time. I am wondering if there were two different flex plates for the 360 and I happened to buy the wrong one? I don't even know what year my 360 is. Maybe I have the wrong one and that is why it is vibrating so much. Does anyone know if there is a different flex plate for different year 360's?

01-02-2007, 01:55 PM	#5
CJ-22 Registered User Join Date: May 2004 Location: Corona CA Posts: 80 Profile Gallery Classifieds My Jeeps	That is a good idea BESRK. I assumed it had a 360 harmonic balancer all along. I'm going to check on it this week to know for sure. Hopefully this will solve my problem and hopefully finding a 360 harmonic balancer will not be too difficult. __________________ 78 CJ-7, 360, 4 inch lift, 33" tires, 4.10 gears, TH 400 tranny, quadratrac t-case, dana 30 front, AMC 20 rear with Superior One Piece Axle.

01-02-2007, 08:42 PM	#6
CJ-22 Registered User Join Date: May 2004 Location: Corona CA Posts: 80 Profile Gallery Classifieds My Jeeps	I have now located the part number to my harmonic balancer. It is 3230130. Does anyone know how to tell if this is to a 304 or 360? I have called numerous auto parts stores and checked all over the internet. I still do not know. Any help is appreciated. __________________ 78 CJ-7, 360, 4 inch lift, 33" tires, 4.10 gears, TH 400 tranny, quadratrac t-case, dana 30 front, AMC 20 rear with Superior One Piece Axle.

01-03-2007, 09:36 PM	#7
CJ-22 Registered User Join Date: May 2004 Location: Corona CA Posts: 80 Profile Gallery Classifieds My Jeeps	Bump. How do you tell which balancer it is? I have found three different balancers online for 360's (none of the part #'s match) and I have found two different balancers for the 304 (none of the part #'s match). I don't want to change it unless I know it is wrong. Anyone know of a website that helps match jeep part #'s? __________________ 78 CJ-7, 360, 4 inch lift, 33" tires, 4.10 gears, TH 400 tranny, quadratrac t-case, dana 30 front, AMC 20 rear with Superior One Piece Axle.

01-04-2007, 03:01 PM	#9
CJ-22 Registered User Join Date: May 2004 Location: Corona CA Posts: 80 Profile Gallery Classifieds My Jeeps	Yes, you can get the number without pulling the flex plate. I had to turn the engine over a couple of times to get the number to the bottom so I could see it. I would really appreciate the help. I have called several places, but these flex plates are no longer available (except from aftermarket dealers, but the numbers are different). Thanks for the help. __________________ 78 CJ-7, 360, 4 inch lift, 33" tires, 4.10 gears, TH 400 tranny, quadratrac t-case, dana 30 front, AMC 20 rear with Superior One Piece Axle.

01-05-2007, 06:29 PM	#12
CJ-22 Registered User Join Date: May 2004 Location: Corona CA Posts: 80 Profile Gallery Classifieds My Jeeps	Okay, I finally found out what I have. My balancer is definitely a 360 balancer, but this puts me back with the same problem. Does anyone know why a 304 flex plate might vibrate considerably less than a 360 flex plate? I'm not an engine expert by any means, so excuse me if this is a dumb question, but could the engine have been rebuilt incorrectly to cause this? Could an internal 304 part been used instead of a 360 part?. __________________ 78 CJ-7, 360, 4 inch lift, 33" tires, 4.10 gears, TH 400 tranny, quadratrac t-case, dana 30 front, AMC 20 rear with Superior One Piece Axle.

01-06-2007, 07:21 PM	#13
CJ-22 Registered User Join Date: May 2004 Location: Corona CA Posts: 80 Profile Gallery Classifieds My Jeeps	Any 360 experts with advice? I don't know what to do next. Should I assume the vibration is not related to the 304 flex plate? __________________ 78 CJ-7, 360, 4 inch lift, 33" tires, 4.10 gears, TH 400 tranny, quadratrac t-case, dana 30 front, AMC 20 rear with Superior One Piece Axle.

01-06-2007, 09:08 PM	#15
CJ-22 Registered User Join Date: May 2004 Location: Corona CA Posts: 80 Profile Gallery Classifieds My Jeeps	Yes they are tight. I have changed the flex plate several times from 304 to 360 to test it and I had the vibration each time. I am wondering if there were two different flex plates for the 360 and I happened to buy the wrong one? I don't even know what year my 360 is. Maybe I have the wrong one and that is why it is vibrating so much. Does anyone know if there is a different flex plate for different year 360's? __________________ 78 CJ-7, 360, 4 inch lift, 33" tires, 4.10 gears, TH 400 tranny, quadratrac t-case, dana 30 front, AMC 20 rear with Superior One Piece Axle.