Flex plate broke. Need Help!

CJ-22 · 03-25-2006, 04:20 PM

Went wheeling last weekend and my TH400 flexplate cracked on two of the three sides. The jeep has a 360 in it now so I ordered the flexplate for the 304 (because that is what it came with), but now I am wondering if it is different. Does anyone know if I will be okay putting a 304 flexplate behind a 360 engine? Are they the same? Thanks for any replies.

fuzz401 · 03-25-2006, 04:32 PM

the balance could be off

John N · 03-25-2006, 09:48 PM

No, no, No......AMCs are externally balanced. You have to use a 360 flywheel. I think I have one out of a '78 Waggy (360/T400) if you're interested....make you a good deal. PM me if interested. You can also have the 304 flexplate rebalanced to 360 specs.

CJ-22 · 03-25-2006, 09:49 PM

That is what I thought, but how do I find out for sure? I have called several shops and cannot get good information. Anyone done a 360 swap who has the correct info?

jpfaris · 03-27-2006, 08:22 AM

I just had a TF 727 rebuilt and had the trans guy order a new flexplate knowing that I was running a 304 now and 360 soon. He and the flex plate people agreed that the same flexplate would work for both engines. I hope they were right. I think the Flex plate came from "Precision". (G111 part number I think) Sorry for the lack of "facts" ,I haven't woke up yet this monday morning.

CJ-22 · 03-27-2006, 05:46 PM

I just got off the phone with a jeep mechanic I really trust. He said the same thing (that it does not matter). He also told me that it would be very obvious if the flexplate was out of balance. There will be a very noticeable vibration. Since I cannot feel a vibration I will not worry.

If anyone out there has better information please let me know. I would greatly appreciate it. Thanks.

jpfaris · 01-23-2007, 10:11 AM

digging up this old thread because now I think I and my transmission rebuilder were wrong about the interchangibility of the 304 vs 360 flexplate. I have a terrible vibration. Searching the net turns up a lot of unsure answers. I deliberately had a 360 flexplate installed because i will be swapping to a 360 one day. Anybody know for a fact that this won't work? If so, please explain. I appreciate all help. (nobody wants to yank out a transmission and put it back to find out the problem was not fixed.)

fuzz401 · 01-23-2007, 11:13 AM

one flex plate has a balance weight and one does not have one

BIG REED · 01-23-2007, 12:08 PM

when i put my 360 in my jeep i took the 360 flex plate and a 304 flywheel to a machine shop and he said he couldnt match balance the 258 or 304 flywheels to the 360 flexplate, (said he would have to add a weight and he wouldnt do it on the flywheel, maybe he would have added the weight to a flexplate though) he said that if i brought him a 360 flywheel or a 401 flywheel he could match them because they both should have a weight to one side.

long story short, they are different flexplates. but maybe they can be match balanced?

03-25-2006, 09:49 PM	#4
CJ-22 Registered User Join Date: May 2004 Location: Corona CA Posts: 80 Profile Gallery Classifieds My Jeeps	That is what I thought, but how do I find out for sure? I have called several shops and cannot get good information. Anyone done a 360 swap who has the correct info? __________________ 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.

03-27-2006, 05:46 PM	#6
CJ-22 Registered User Join Date: May 2004 Location: Corona CA Posts: 80 Profile Gallery Classifieds My Jeeps	I just got off the phone with a jeep mechanic I really trust. He said the same thing (that it does not matter). He also told me that it would be very obvious if the flexplate was out of balance. There will be a very noticeable vibration. Since I cannot feel a vibration I will not worry. If anyone out there has better information please let me know. I would greatly appreciate it. Thanks. __________________ 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.