1996 Mustang Cobra vibration at certain rpms.

96moonlightblue · 03-05-2009

Ok, so the shop just got my cobra back togather and gave me a call. The tranny was bad so I had it rebulit. Also I just had the clutch done and there was some virbration at ceratin rpms most notiveable right above idle inbetween 900-1000. I thought when they did the clutch that the flywheel might of been surfaced un evenly this was the case but it did not solve the issue. The car as had alot of work done lately.

New clutch,new spark plugs, Spark plug wires,Energy suspeion Engine mounts,transmisson mount,fuel filter,IAC valve,TPS EGR valve cleaned. Transmisson as been rebulit main shaft was bent so this was also replaced. The flywheel was machined out of spec so they had it resurfaced. I have not gotten it back but the shop e-mailed me and said the virbration was better but still present. I also had some underdrive pully's on it so I switched it back to the OEM ones. This did not help. No idea where to go next, Coil packs maybe? Any input would be awesome.

daboyho50 · 03-06-2009

Ouch man, I'd be pullin my hair out. . . I've got nothin.

2oo5GT · 03-06-2009

Could be incorrectly gapped plugs, bad driveshaft or bad ujoints. that's all i can think of right now.

96moonlightblue · 03-06-2009

I forgot that part drive shaft as been replaced with a ford racing from american muscle. I'm think gap on spark plugs. As i have heard this a couple times. They will be coming out twmr. I'am pulling my hair out but right now i'm just glad to have my car back after 2 weeks with out it.

96moonlightblue · 03-06-2009

I just started it in the garage with the lights off and some sparks are jumping from the wire to the alt and too the valve cover. Its a blue spark. I just replaced these wires though. I guess I must of got a bad set.

66restomod · 03-10-2009

sounds like the insulation on the wires is leaking, replace them and you should be good, another way to test for leaking secondary ignition is in low light, lightly mist water out of a windex bottle onto the coils and around the wires down to the plugs, watch for the spark to jump.

96moonlightblue · 03-10-2009

Replaced them still no luck. Found a old thread that described my problem to a T. The guy replaced the harmonic balancer and that solved the issue. So I ordered a OEM on today see if that solves the issue fingers crossed because if it don't I'm out of ideas. Mine does have the rubber coming out of it about a 1/4 of a inch in two places so I have high hopes for this. I would of tired this sooner but I replaced the underdrive with the the orginal and it still did not help but I gues the oem got beat up laying in the tool box.

66restomod · 03-10-2009

ya the balancer could have spun, had it happen on a 302 from a Merc, but it wouldnt run at all.

96moonlightblue · 03-12-2009

The harmonic balancer helped a ton. Still got a slight shake but I would not even call it a vibration at all. guess it probabaly comes with the stiff energy suspension mounts. Also got a high speed vibration but I'm thinking that is just do to the 4:10's. This is hope for the cobra yet.

66restomod · 03-12-2009

high speed vibration? all the tires in perfect balance?

96moonlightblue · 03-12-2009

Yeah all the tires are great just had them rebalanced a week ago. It sounds like a drive shaft out of balance. I might be 180 Degress out I guess I'll try turning that twmr. Its fine all the way up to 95 then about 100 starts getting the vibration.

96moonlightblue · 03-12-2009

Ok just noticed something after searching the fourm. When I installed my new drive shaft i just put it in. Used the same bolt holes that the old drive shaft used. I did not use any aligment mark as I have heard mentioned in some other post. What is this and how do I line it up. There was no mention of it on the tech article that I read on american muscle.

96moonlightblue · 03-13-2009

Well clocking the drive shaft 180 did not help in fact I think it made it a little worse at high speeds and a little better below 80. It looks like a weight might of got knocked off the drive shaft. E-mailed american muscle about it I have only had the drive shaft for like 20 days and it just got installed,

This has been really frustrating. It did none of this before the gear install. I had the gears swapped the issue started gears are quite and don't whine at all. I got the drive shaft issue was still there. So I took it back to the shop that did the gears they said everything was fine with the rear end and the issue was with the transmission tail shaft bearing. So I paid the 1100 bucks to have the tranny rebulit. Get it back shift smooths and great but still have this annoying "womp womp womp" at 60 then shakes the crap out of the car above 95. In the last two months the car has had a complete tune up, tires all balanced, new wheel bearings in the front,Brakes all around, Drive shaft. Rear end rebulit, tranny rebulit,new harmoni balancer,IAC,TPS new transmisson and engine mounts. I really sure it is the drive shaft well see I guess. This is getting old really quick. I guess it I'm wrong about the drive shaft which I doubt at that point it will be time for some new wheel bearing in the back and after that I have no idea. Maybe have another shop look at the rear end although this shop seems to be good. They have not had any issue double checking everything. I trust them I just don't know why I can not get this think to stop vibrating. I was about to just deal with it but then drove it and remembered how bad it was.

96moonlightblue · 03-14-2009

I changed the rear wheel bearings and this helped a ton. Good until 120 now. Which at 120 i'm thinking there is going to be a little vibration. Note(This speed was done on a closed airport run way.))