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70 390 Vibration following clutch job |
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uncljohn
AMC Addicted Joined: Jan/03/2013 Location: Peoria AZ Status: Offline Points: 5394 |
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Being as the AMC engine is supposed to be externally balanced which means the balance weights are supposed to be part of the harmonic balancer and the flywheel, do you know whether you had the whole assembly neutral balanced as some people seem so inclined to do so it creates a Franken Engine or whether you had it balanced as it was intended to be. And if so have any of the changes made since then affected things.
Also if there is any possibility that the harmonic balancer outer ring rotated due to rubber degradation throwing the whole mess out of balance? |
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70 390 5spd Donohue
74 Hornet In restoration 76 Hornet, 5.7L Mercury Marine Power 80 Fuel Injected I6 Spirit 74 232 I-6, 4bbl, 270HL Isky Cam |
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indcontrols
AMC Fan Joined: Mar/26/2014 Location: South Florida Status: Offline Points: 22 |
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I had the engine balanced as it was intended, using an NOS damper and the original flywheel. I did inspect the balancer this morning, did not see any signs of slippage or damage.
I have been running this motor for a while now without any issues, but when the wife & daughters went away to visit family (hence I had no adult supervision) - I went out and had too good of a time and smoked the clutch.... get them hot enough and eventually even Mickey Thompsons will grab pretty well...
I had the flywheel resurfaced by a reputable shop. I know it's my flywheel because I had stamped the engine build date in the flywheel. I replaced the clutch with a RAM kit - pressure plate, disc, release bearing.
The vibration is small, but definitely there. It is a street motor, but I run the living *&$% out of it, looks like I'm going to have to pull it apart. I truly love this motor - it performs like a hero - I guess I will take it to Mesa and get it balanced... or I might just change the clutch assembly again. Just really wierd, I have had many hotrods, and I am definitely a "third pedal" guy - just never had a balance issue from a clutch before !
Last night I had a local kid (who has a newer Camaro) suggest to me that I should "put a chevy in it"... I have to get this sorted out so I can go adjust his viewpoint to the wagon's tailgate...
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indcontrols
AMC Fan Joined: Mar/26/2014 Location: South Florida Status: Offline Points: 22 |
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Unclejohn - I see you have a 70 390 5spd Donahue - what 5 speed setup and bell did you use ? I could always use another gear... and I am obviously going back into the clutch...
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uncljohn
AMC Addicted Joined: Jan/03/2013 Location: Peoria AZ Status: Offline Points: 5394 |
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I using the Ford Mustang T5, what is called the World Class version for the V8 engine and was used from 1987 through 1993. The bell housing is generally called the Multi-bell, used by AMC on their T-4 and T-5 equipped cars. Multi-bell in that it could be found being used on other 3 speed transmissions during the same time interval.
And you want to be some what careful before making a decision to use something like this in that the gear ratio of 1st is quite low, 4th of course is 1:1 and over drive is exactly that. Working from memory about .75. I'd have to look up the specifications. The point is when doing something like this you want to take into account your rear axle gearing in that if you are planning on keeping the 3.54 OEM final drive, bolting on this transmission with out further though gives you the following: 1st becomes functionally a Granny Gear. 2nd through 4th becomes a wide ratio 3 speed and 5th becomes an overdrive. To make this a functional conversion your rear axle gearing becomes about a low 3:XX or a high 2.XX in order to get a workable 5 gear set up. Those who ignore this generally discover that they were better off not doing it at all. I am using a 3.15:1 positraction rear axle and the gearing works out quite well for me with road speed in 5th about 32mph/1000 rpm which is quite typical these days for multi-geared OEM cars. The other thing to keep in mind is that the transmissions are not rated very high in torque. So if you plan on beating it, death will come early. I have hear another set up I can assemble one from except in this case I have the same transmission but one as used from a Merkur the German car ford broad in but re-engined it with the Turbo-4 which was also used in T-Birds. The gear ratio's are even wider as 1st and 2nd gearing is even lower than the V8 version. It would have to rebuilt with differnt 1st and 2nd ratio's and when doing that, those values can be selected to be better which both changes the transmission to make it more useful with a short geared rear axle and also improves the torque rating. There are other a couple of other things that can be done to improve the reliability too. But realize again these are now old transmissions and technology has both changed and newer options are open that may not have existed in 1991 or 2 or so when I assembled this. The whole thing is ALMOST a bolt in on an AMC engine and car IF yours already is a standard transmission equipped in the first place and you have a broken T-4 for parts, although that is not absolute, just handy. I've had no problem with mine and would do it over again in a NY min. But, I don't beat on it. Mine was a 4 speed car and the 4 speed wore out and rather than rebuild it the 5 speed made it much more happier on the South West high speed interstate roads. |
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70 390 5spd Donohue
74 Hornet In restoration 76 Hornet, 5.7L Mercury Marine Power 80 Fuel Injected I6 Spirit 74 232 I-6, 4bbl, 270HL Isky Cam |
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indcontrols
AMC Fan Joined: Mar/26/2014 Location: South Florida Status: Offline Points: 22 |
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Yeah, I had eyeballed the world class T5 when I put the car together, but decided to put "all the right stuff" in the T-10 instead. I am doing more travelling to cruise ins and shows than I expected to, which is why I am thinking about another gear. I think I would definitely break up the T5. I think a TKO 600 is in my future, I guess I had better start adding to the penny jar... I run a 4:88 with 29.5" tall tires, people are doing 80 on rt. 95 down here in FL., they're running me over !
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uncljohn
AMC Addicted Joined: Jan/03/2013 Location: Peoria AZ Status: Offline Points: 5394 |
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It is self evident with out argument that a 4.88 is not a street gear for cruising. And it can be said a 2 speed power glide makes a good drag racing transmission if you only want to run a quarter a mile at a time.
Multiple gears gives you a low for acceleration and a high for freeway driving and the middle gives you flexible driving. But you can really screw that up by choosing the wrong rear axle gears. With what you have at the moment the only viable solution would be a gear vendors overdrive which takes care of the cruising gear ratio and leaves low alone. My Donohue is a nice running 390 built to be a tunable street engine and frankly can be tuned to pass smog and MUST run on 91 octane which is the premium gasoline out of the street corner pump. You have 94 octane out of the street corner pump in Florida. That says the engine can be different, but it won't run well on 91 octane. As a street motor mine is fast and reliable. The gearing and the transmission lets it be that way. I've owned it since 1979 and it has seen a quarter mile about 2 miles worth during that time, which is enough for me. Cheers and have a good day. |
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70 390 5spd Donohue
74 Hornet In restoration 76 Hornet, 5.7L Mercury Marine Power 80 Fuel Injected I6 Spirit 74 232 I-6, 4bbl, 270HL Isky Cam |
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