What will cause vibrations above 4k rpm?

[StangBangRicers]

It's definetly rpm induced and only when I stomp on it and let it get above 4k rpms. Whole car starts vibrating and makes me cringe... It's an auto and before my rear gear change it never got much above 3k now that I'm hiting the 4k+ zone... I've started to notice it.

I'm thinking it must be the balancer. I checked the timing and it seems accurate, so I don't think it has spun.

Any other suggestions or possiblities before I replace the balancer?

 

[IndyBlk5.0]

when your at idle does the balancer wobble around? only thing that could make a vibration like that is a rotating mass... balancer is my guess.

 

[StangBangRicers]

It does seem to wobble a bit... but I'm not sure if it's actually the balancer or just the weight creating an optical illusion.

I think I may just replace it for the hell of it anyways....

 

[5spd GT]

I'd be willing to bet it was the harmonic balancer as stated...you might ought to check your driveshaft...maybe it got warped somehow????

David

 

[banditmwp]

I had the same problem after replacing the gears, and it turned out to be the driveshaft. I replaced it with an aluminum shaft and the vibration disappeared. Does it vibrate if youre in park/neutral and rev it up to 4k? If not, then i would go with the shaft...if it does vibrate in park, it's probably the balancer.

 

[banditmwp]

another way to check is to put it in neutral when you reach where it starts vibrating on the road...if the wheels are going 80 and the engine is only spinning 800 rpm and you still have a vibration, then your driveshaft is warped or missing a counterweight.

 

[StangBangRicers]

It still vibrates in park... gonna replace the balancer.

Thanks folks.

 

[UnderPressureGT]

dumb thing, but i had the same prob as u.. vibrations after 4K.. turned out that my stock clutch fan was shot... just take your belt off and rev it up and see if the vibrations gone

 

[90mustangGT]

Most likley the Harmonic Balancer/Dampener. Get a SFI aproved one, trust me, it's worth it. The stock one is only rated to 4500rpm and still isn't very good. It is just two iron rings with a rubber layer in the middle. I put a Romac on mine and it is a noticable difference. First of all, it looks alot better, i wouldn't care if looked like poo as well as it works. I never really had any engine vibration, but I noticed it was wobbling. I just couldn't drive knowing the balancer was about to self destruct. When I put on the Romac, I was suprised of how smoothly it revves. I can be at 5500rpm's and it car feels as though it was at 2000rpms, the only way I can tell is be the tach reading and the exaust note. Harmonics reek havoc on main berrings.

dumb thing, but i had the same prob as u.. vibrations after 4K.. turned out that my stock clutch fan was shot... just take your belt off and rev it up and see if the vibrations gone

Good point, it isn't very likley but a possiblity.

Another possiblilty is the flexplate, I have scene them warp and cause all kinds of vibration, but once again, not likley.

 

[HISSIN50]

dont mean to jack the thread, but it sounds like it will be pertinent to SBR, and there is a knowledgable audience already here.

what balancer do you like? who has the best price? i dont mind less extreme units - dont see over 3K hardly ever.

 

[StangBangRicers]

dumb thing, but i had the same prob as u.. vibrations after 4K.. turned out that my stock clutch fan was shot... just take your belt off and rev it up and see if the vibrations gone

I didn't have a chance till today to yank the belt.
Sure enough... no vibrations.

You rock man!

 

[85_SS_302_Coupe]

replace the balancer anyways if you have the cash. If it's stock it could be on it's way out someday soon, and new ones make your engine run so smooth it's well worth the purchase