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Unread 09-08-2010, 09:08 AM   #1
RjTack
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1985 CJ7 
 
Join Date: Aug 2010
Location: Central/Western, New York
Posts: 275
304 auto/manual flywheel/flexplate

Hi All,
Is the flex plate/ flywheel the same for the auto tranny as the manual? I'm swapping in a 304 that was hooked to a manual 3-speed to my '85 CJ7 that had a 258 and has an auto trans. Do I need to locate a flywheel from a 304/Auto trans, or will the torque converter bolt up to a 304 manual trans flywheel?

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Unread 09-08-2010, 09:19 AM   #2
BioTex
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2006 TJ Wrangler 
 
Join Date: May 2008
Location: Alpine, Tx.
Posts: 3,173
Automatics have flex plates. Standards have flywheels. You need a flexplate balanced for a 304 behind the motor, to go with an automatic. Hope this helps.

Edit:
While you have it apart, don't forget to change the pilot bushing/bearing.
__________________
'85 CJ7, BDS 4" lift, 1" Body lift, 33x12.5, Shrockworks Sliders, 304 V8 with RV cam., T-176, D300, Dana 30, AMC 20.
1986 CJ10-A SD-33 Diesel/727/np208
1971 800B with 345/T-19
06' TJ Rubicon, 4" R.C. springs, BFG/AT 35s M.C. 6" fenders, rockers and surrounds, Currie front & rear adj. tracbars, tattons DC rear shaft, adj. upper - lower CA's. Bilstein 5100's
YJ Buggy Build Current project. Stroker/FI ?
1990 MJ Comanche 4.0L AX15/np231
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Unread 09-08-2010, 09:55 AM   #3
RjTack
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Join Date: Aug 2010
Location: Central/Western, New York
Posts: 275
Flex plate re-balancing

Anyone know if I can get my 258 flex plate re-balanced to use with a 304? If so were would I get that done?
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Unread 09-08-2010, 10:01 AM   #4
BioTex
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2006 TJ Wrangler 
 
Join Date: May 2008
Location: Alpine, Tx.
Posts: 3,173
Post in the wanted section of the classifieds on this forum. That's where I got one. Re-balancing is done at a machine shop. Cheaper to purchase a used one probably. I'm not certain if it is possible to do without the crankshaft out.
__________________
'85 CJ7, BDS 4" lift, 1" Body lift, 33x12.5, Shrockworks Sliders, 304 V8 with RV cam., T-176, D300, Dana 30, AMC 20.
1986 CJ10-A SD-33 Diesel/727/np208
1971 800B with 345/T-19
06' TJ Rubicon, 4" R.C. springs, BFG/AT 35s M.C. 6" fenders, rockers and surrounds, Currie front & rear adj. tracbars, tattons DC rear shaft, adj. upper - lower CA's. Bilstein 5100's
YJ Buggy Build Current project. Stroker/FI ?
1990 MJ Comanche 4.0L AX15/np231
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Unread 09-08-2010, 12:37 PM   #5
h2ojeep
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1978 CJ7 
 
Join Date: Oct 2008
Location: Cottonflat, TX
Posts: 677
Each AMC engine has a unique harmonic balancer and flexplate (fly wheel if standard transmission) and cannot be mixed between different types of engines. A 258 cannot be put on a 304, 304 cannot be put on a 360 etc. However a they can be changed between the same engine, 304 from one engine will go to another 304.

So as Biotex said, you might do better finding a used flexplate from another 304 verse the expense and logistics of balancing .

New is not all that bad a price

Flywheel, Automatic Transmission 8 Cyl AMC 304*5351820 by the Jeep Specialists | Morris 4x4 Center

Hope this helps
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Unread 09-09-2010, 08:41 AM   #6
Supertrucker
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1979 CJ5 
 
Join Date: Jun 2008
Location: Kentucky
Posts: 59
Don't know exactly where you are, but I have a 304 flexplate I just removed from the motor I am dropping in my CJ5. It's yours if you want it, just pick it up or pay shipping and I will get it on it's way to you. Let me know, I will be back on here tomorrow night or sometime Friday.
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Unread 09-11-2010, 12:03 PM   #7
Supertrucker
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Location: Kentucky
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PM sent. Sorry for taking so long to get back to you. I broke down on the way home and spent last night at a lovely diesel shop in Lexington, Ky. I'll let you know what shipping costs Monday morning.
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304 , auto trans , flexplate , flywheel , torque converter
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