Vibration at high rpm's under acceleration

[87lc2]

When reaching about 4k rpms in any gear the car starts to vibrate badly and seems to make much less power. I just rebuilt the rear about a month ago, and the driveshaft and u joints are all tight. What else could this be? Motor mounts? they look ok.....anyhelp appreciated

 

[BlownFiveLiter]

Sounds like a bad balancer. If it's the stock one, they go bad all the time, when the rubber dries out over time. The outer ring probably spun, since it's bonded to the balancer by the rubber. I wouldn't drive the car until it's inspected/replaced, unless you have a new shortblock in your near future plans.

 

[87lc2]

wow, didnt think they went bad....sounds right though as i cant even spin wheels in first, the engine just revs.....i have an u nderdrive kit i was going to put on, would that fix it?

 

[87lc2]

is there anyway i can tell its bad for sure?

 

[FiveOfastback]

is there anyway i can tell its bad for sure?

Yeah! Replace it! No! the underdrive kit doesn't have anything to do with balance

 

[peak-j]

Vibration

I have an 89 Mustang GT, I have had the same problem in the past. First mine was the driveshaft, it was bent a little bit. Second time, it was my clutch coming apart. When I pulled the bellhousing pieces of the clutch fell out. Had a hell of a mess. It vibrated like hell when you got on throttle hard. Hope this helps.

 

[jackchan]

humm i wonder if my balencer is bad and that is what caused the starter bolts to vibrate loose and not my solid motor mounts? will have to check that!
thanks
Jack

 

[mr.b]

put a chalk mark across the hub to the ring. drive it around, if the lines start to move around from each other the outer ring is moving and that will tell you it is not in the greatest condition.

 

[jackchan]

thats a good idea.............i usually paint my balencer white........then use a pencil to mark the balencer or a black sharpie....that was there is no problem finding your marks!
Jack

 

[87lc2]

yea, i looked under the car and the rubber is not coming out, but its cracked up pretty good and dry rotted. i was just going to put a stock replacement from the parts store on.....should that be ok? also, ive taken balancers from other cars off in the past and did not neet a puller, it just came off after the crank pulley was removed. are these cars different?

 

[BlownFiveLiter]

You'll almost certainly need a puller to get it off, but especially to get the new one back on. Personally, I'd spend a few bucks and get an SFI approved one like a Romac or something. Get one that you won't need to replace again and you'll be set.

 

[87lc2]

where can i get an SFI balancer? (sorry, new to stangs) also, why would a puller be needed to put it on? they just slide on over the notch

 

[Paul Perreca]

maybe it's the driveshaft, after people do the rear, and put gears in, alot of the time theres vibration and it's fixed with an aluminum driveshaft swap