BAD vibration at 1800rpm

NoVaEaTeR

NoVaEaTeR

New Member
Apr 21, 2004
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#1
ok so i did some searching and didnt come up with anything that sounded related to my situation so i thought i would ask for some input. I have a 68 mustang i just put my 289(fresh rebuild) and a t-5 in it and after eating a cam i got the engine running fine and smooth except for the fact that it has a really bad vibration( more like a really bad shaking) that starts at about 1800rpm. Its really bad so i am thinking that it has to be something big to make it that noticable, ie HB? flywheel? or clutch? It does it parked, driving, in gear and out of gear so that tells me it is something from the clutch forward right? i know i have a 28oz HB and flywheel, and the flywheel only goes on one way right? so my question is does the pressure plate only go on one way? there were no alignment pins on the flywheel for the pressure plate does there need to be? and the last question is would the Harmonic balancer shake the whole car like this? thanks for any input!

Pat:SNSign:
 
#5
1320Stang: yes it still does it with the clutch pedal all the way down.

1.)t year was the last year they used a 28oz cb?

2.)ld the Harmonic dampner produced a vibration that shakes the poop out of the car?
 
#8
Right now, my guess is that the outer ring of the harmonic balancer has spun on the inner ring creating the imbalance. I'd try a new balancer, or at least inspect the old one, make sure the rubber is good. One way to check for shift is to confirm the timing is correct. A few degrees off would make too much difference as far as vibration, but a loose outer is an accident waiting to happen.
 
#12
I did a recent drivetrain upgrade with a 347 and T5 swap and I am also experiencing a vibration similar to yours. I got a new HB, although it was fairly low end - Professional Products I belie and ran about $90. I also got a new Flywheel and paid about the same and have been suspecting the FW may not have been within spec. Both were supposed to be 28oz. My mechaninc had my transmission and clutch off to resolve a scraping issue with my block plate (I just love working the bugs out of these projects) and made a comment that the counter weight on the FW looked really big. Unfortunately, we didn't really identify or start troubleshooting the vibration problem until after he had everything back together. I'm gonna have to pull it apart again, but may not get to it for a while now that winter is here. You mention your FW was replaced and resurfaced, where did you get your FW?
 
#13
hb is brand new from a local frp store and i am 100% sure it is 28oz. so that rules out outer ring shift. i got the flywheel from a friend. i remember looking at the year code on it and i cant remember what it was but i was sure when i looked at it that it was a 28oz year, but again i didnt write the year down so i am not 100% of th cb of the fw. so i am gonna do a comp. test and be sure its not the engine then i will drop the tranny. but can anyone tell me does the clutch pressure plate have to go on only one way? i mean does it have a counter balance to it that if installed wrong would shake the poop out of the car when i take the rpms up?
 
#14
NoVaEaTeR said:
i got the flywheel from a friend. i remember looking at the year code on it and i cant remember what it was but i was sure when i looked at it that it was a 28oz year, but again i didnt write the year down so i am not 100% of th cb of the fw......but can anyone tell me does the clutch pressure plate have to go on only one way? i mean does it have a counter balance to it that if installed wrong would shake the poop out of the car when i take the rpms up?
Click to expand...

The clutch is not balance-dependent so that can be ruled out. Since you don't have definite numbers for the flywheel, I would suspect that. It's not always the easiest to I.D. a flywheel balance weight just by looks. If it helps, the switch from 28oz to 50oz was made no earlier than the late '70s.
 
#18
no i did not get the hb fw and crank balanced because i was told by the machine shop that i use that it is only needed if i am going to be taking it above 6000rpm, and that as long as i get the right imbalance parts(ie hb and fw) that it will be fine because thats how they came factory.
 
#19
did you check to make sure the exaust or anything on the motor isn't coming in contact with the car?

First Id pull the harmonic balancer and check it out...looks like you're going to have to end up dropping the trans though. Not that big of a deal since the t5 is so light. I had a badly spun harmonic balancer on my 66 mustang and the vibrations werent as bad as it seems like yours are.
 
#20
good news and bad news all at once! i pulled the tranny and flywheel and looked at the date and yup its an E1(81) which is the first year ford started the 50oz cb. so thats good that i found out what is wrong but it sucks cuz now i need to get 200 for a new flywheel:nonono: how much do these 81 50oz flywheels sell for? new ring gear and resurfaced? thanks for all the input.:flag:
 
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