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Auto Tran to Man swap violent shake |
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chrizti4
AMC Fan Joined: Jul/01/2019 Location: Wentzville, MO. Status: Offline Points: 14 |
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Posted: Jul/02/2019 at 9:14am |
AMC Friends, I'm stumped! 1978 CJ7, removed 304 3spd swapped in running (78?) 360 out of a J10 auto. Ordered flywheel and input shaft bushing and installed working 5spd. Engine starts fine, no odd sounds from starter or anything. At 800 rpm shakes violently till around 3k (didn't go higher than that). Engine responds like its new, no blow by, no burning oil on accel or de-accel. Vac gauge at a solid stable 16lbs needle has no waiver or shake, timing and firing order checked four times, 5degBTDC with ported line attached. Changed plugs, wires, dist cap. Header temp only varies <50deg between pipes. Don't want to (shouldn't) drive it with SHAKING the whole jeep. Doesn't overheat, stays a good 165. Carb flow checked, and everything within standards. After warmed up did rev it a bit, sounds fantastic with both open headers and with mufflers installed, shaking doesn't change. But at idle smooth as a kitten and when hitting accelerator smooth as a tiger. Have built a lot of vehicles, this is second AMC build. I AM STUMPED! I know some say the 401 has a different flywheel, but I ordered one for a 360. Next step is dropping drive-train, installing the old flex-plate, building a temp rear block mount and starting the engine again. Is there anyway to tell if the flywheel is the wrong one? Thank you sir!
Respectfully submitted, Christopher Wuertz
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ramblinrev
Moderator Group Joined: Dec/28/2008 Location: Wisconsin Status: Offline Points: 11469 |
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Yes, sounds like you have an engine balance issue. The manual flywheel (correct or not) is not going to have the same balance as an automatic flexplate.
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74 Hornet Hatchback X twins (since 1977)
62 American Convertible (still worth the $50 I spent in 1973!) AMCRC #513, AMO #384 70 AMX 360 4-speed (since 1981) |
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chrizti4
AMC Fan Joined: Jul/01/2019 Location: Wentzville, MO. Status: Offline Points: 14 |
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Thank you sir for the response, how do I fix this?
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tufcj
Supporter of TheAMCForum Supporter of TheAMCForum Joined: Jul/10/2007 Location: Watkins, CO Status: Offline Points: 4065 |
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Did you use the 304 flywheel or order one for a 360? AMC V-8s are externally balanced. The flywheel (and harmonic balancer) have to be for your specific displacement. If you still have the automatic flexplate that came off the 360, you can take that and the flywheel to an automotive machine shop and have them "match balanced". Bob tufcj
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69 AMX
74 Javelin AMX 67 Rogue If you need a tool and don't buy it... you'll eventually pay for it... and not have it. Henry Ford |
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BrotherBamc
Supporter of TheAMCForum Joined: Jan/22/2009 Location: Lewiston Status: Offline Points: 2248 |
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Have your flywheel neutral balanced...
A reputable machine shop that does balancing will be able to help you out with that.
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SC397
AMC Addicted Joined: Apr/30/2009 Location: Michigan Status: Offline Points: 5428 |
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A pleasure to meet you Mr. Stumped, If you have the original flex plate from the 360 you could have a machine shop match-balance the new flywheel to the old flex plate. Or, disassemble the engine and have a machine shop externally balance the rotating assembly.
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mark09
AMC Nut Joined: Dec/14/2012 Location: indiana Status: Offline Points: 279 |
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Brotherbamc there's a big difference between neutral and match balance.
V-8 's not neutral ballance unless specifically done at a rebuild .
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Greyhounds_AMX
AMC Addicted Joined: Nov/14/2009 Location: Kansas City Status: Offline Points: 1268 |
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They actually would have the same balance. When I converted from auto to stick, I had my new flywheel match balanced to the old flexplate. My engine had previously been rebuilt and rebalanced, so stock balance weighting didn't apply anymore. I recently had a friend with a similar problem and it turned out to be the clutch/pressure plate that was the culprit. You might try it with the clutch and pressure plate removed but keep the current flywheel and see what happens.
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1968 AMX 390 w/T5
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BrotherBamc
Supporter of TheAMCForum Joined: Jan/22/2009 Location: Lewiston Status: Offline Points: 2248 |
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I stand corrected then... I had a 360 flywheel "neutral balanced" when I put a T-10 behind my 258. I believe that the 258's are externally balanced then..?? |
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tufcj
Supporter of TheAMCForum Supporter of TheAMCForum Joined: Jul/10/2007 Location: Watkins, CO Status: Offline Points: 4065 |
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Neutral balance is correct on an I-6. Those are INTERNALLY balanced. V-8s are EXTERNALLY balanced and rely on the harmonic balancer and flywheel/flexplate for balancing. Bob tufcj
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69 AMX
74 Javelin AMX 67 Rogue If you need a tool and don't buy it... you'll eventually pay for it... and not have it. Henry Ford |
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