Bad Shaking

[DKeen]

My car gets a terrible vibration when accelerating, as soon as it gets above 3.5-4k rpms it gets horrible. Before that its pretty docile and drivable, not too noticable. I really think Its something under the car rubbing against something else, but i cant seem to pick it out. (thats the nature/feeling/sound of it) would this happen if the driveshaft was hitting the exhaust maybe?

My exshuat rubs against the framerail, and I tied it away from it, and the shaking was still there. I cant tell if the driveshaft rubs, because it moves up and down when i jack/lower the car. It does it when accelerating (over 3.5 mainly again) but also when I rev up to that standing still in neutral.

any ideas anyone? recently replaced the motor mounts/harmonic balancer and a few other things. its just getting old trying to figure this out, and it definitely feels like its under the car. thanks

 

[5ive.oh]

Clutch?

 

[bill302]

my exhaust was hitting my driveshaft and here are the marks it left....if yours is hitting it will have similar marks..but it could be a number of things u-joints, tranny mounts,unbalanced driveshaft,wheel unbalanced,front end alignmentect....run a search on this site alot of people here has had similar problems some have solved them and some never do...you need to know if it vibrates when accelerating or/and decelerating clutch in or out or/and while coasting.when exactly does it begin and end example accelerating above 3.5 rpm's and stops imediately when you apply clutch....and post results..

View attachment 457108
View attachment 457110

 

[DKeen]

my exhaust was hitting my driveshaft and here are the marks it left....if yours is hitting it will have similar marks..but it could be a number of things u-joints, tranny mounts,unbalanced driveshaft,wheel unbalanced,front end alignmentect....run a search on this site alot of people here has had similar problems some have solved them and some never do...you need to know if it vibrates when accelerating or/and decelerating clutch in or out or/and while coasting.when exactly does it begin and end example accelerating above 3.5 rpm's and stops imediately when you apply clutch....and post results..

View attachment 457104
View attachment 457106

I'll have to check for those marks tomorrow, but to answer some questions:
-I plan to re check the tranny mount, but it seemed fine.
-wheel unblanced and front end alignment are out, because it does it when I'm sitting still in neutral when revving up.
-doesnt shake at all while coasting cluch in, rumbles lightly whole driving at lower rpms, feels like a jackhammer when punching it above 3, shifter tries to shake my arm off. does it when accelerating at mid-high rpms and also when decelerating down in the higher rpms too. (compression braking only).
-don't know much about u joints, but would they still make it happen sitting still and revving?
-ran tons of searches, having a hard time finding another with the same thing.

thanks again.

 

[DKeen]

oooh also, This car has a 351w in it, I bought it that way and it had recently had a new tranny put in. While I did add a new balancer trying to fix this, would it behave like this if the shop didn't put in the right balanced flywheel maybe?

 

[bill302]

with the info. above that would rule out anything basically from the tranny back....i would think either a balance or motor mount problem did it do it before the balancer installation and exactally which balancer did you install and i would recheck the motor mounts and could it be a miss in the engine?

 

[bill302]

oooh also, This car has a 351w in it, I bought it that way and it had recently had a new tranny put in. While I did add a new balancer trying to fix this, would it behave like this if the shop didn't put in the right balanced flywheel maybe?

exactly you may have the wrong balancer for your flywheel or viceversa...did you install a 28 oz. balancer and i'm not a professional on this matter but maybe someone else will post with more experience but i believe if the balance is off you can damage a motor especially if its as bad as you say and if it is in fact a balance problem...i would not drive the car until verified and fixed.

 

[DKeen]

well its a 351w, so the balancer I got is a 28 oz (the one on there was too, and the vibe was present before I switched them.

The motor mounts I just replaced (again, trying to solve this)

I have a growing suspicion that it might have the wrong flywheel for the motor. (50 oz flywheel with the 28 oz balancer)

if that were the case, would it seem to drive okay at some rpms, but be exceptionally violent at others? or would it suck all the time, thats what I'm wondering now.

 

[bill302]

if that were the case, would it seem to drive okay at some rpms, but be exceptionally violent at others i believe this statement is correct...but it seems that fastdriver in the link i posted below is more knowledgable on this subject and he is online maybe he will step in or you can send him a private message...
http://forums.stangnet.com/showthread.php?t=646794

 

[DKeen]

if that were the case, would it seem to drive okay at some rpms, but be exceptionally violent at others i believe this statement is correct...but it seems that fastdriver in the link i posted below is more knowledgable on this subject and he is online maybe he will step in or you can send him a private message...
http://forums.stangnet.com/showthread.php?t=646794

thanks, pmed him

 

[bill302]

was he able to help you....keep me updated.thanks

 

[DKeen]

he asked me to do a few things, waiting for him to get back to me. in the meantime I have suceeded only in confusing myself more:

I found the casting on my block, it says d9ae, which makes my motor a 1979 (28 oz balanced) for some reason though, I realized that the balancer only fit on it right with the 1980+ spacer... so that seems a little whacky..

anyone have any ideas?