92'GT 5spd, I get a realy bad vibration when I try to accellerate. The vibration is bad enough that i feel it through the seat, the shifter, and even the floor. Don't seem to notice it while at idle (only had the car for 6 months and it has idled a little rough since purchesing). Any ideas?

 

Bad u-joint or bent driveshaft. Probably u-joint.

 

Like AlsCobra check the u-joints but also check tranny mounts and motor mounts. when these go they can change the pinion angle, some cars react different than others meaning the vibration can be more suttle or worse. If it is the driveshaft( even my steel one had a slight vibration) get an aluminum either ford racing (i'm running this one) or for cheaper awd aerostar van (not the 2wd too long) change out the u-joints and use your yoke, use u-joint parts

Precision Regular U-Joint, Greasable, PCN-353 from summit racing or
Precisoin Super U-Joint, Greasable, PCN-275 from summit racing

If you still have issues then we will have to go deeper. The aluminum DS is a known vibration cure for the fox over the steel unit.

 

U-joints are cheaper than drive shafts so I'll start there. Thanks for the help.

 

When you pull the driveshaft, you should be able to tell if the joints are bad.

 

YUP, MY 89 did the same thing......

 

Check if the flywheel is surfaced correctly.

 

Bad harmonic balancer?

 

If the vibration is only on acceleration, it's driveshaft/ujoint every time.

 

+1. all the symptoms of a bad u-joint like we stated or at the very least a possible bad DS. MstngMikeGT a bad HB would cause problems at idle also. 92CornerCarver go for the u-joints 1st if you don't want the summit ones napa has a good set also but get thier high end ones they are much better, if the vibration is still there then look towards the drive shaft. you have a couple of options the aluminum option like I gave or you probally have a driveshaft shop in your area that can check it and rebalance it also.also check the DS angle. keep us posted.

 

Ordering a Heavy duty U-joint from Latemodelrestoration.com. Once it gets here and I install it I'll let y'all know how it turns out. Thanks again for all your help.

 

Ok, so I checked the U-joints and they where not the source of the problem. After talking with my father in-law he said that his Ford truck had the same issue about a month prior and he had to replace his spark plugs and coil packs. So, after replacing the rotor, rotor cap, plug wires, and plugs I am glad to report the vibrations have vanished.

 

So what you are saying is that you havent done a tune up in awhile right?

J/K man . glad you got it taken care of with little money spent.

 

I'm glad it worked out. check your motor mounts, that was alot vibration you described for just a tune up to fix unless the motor was jumping enough to transmit it through weak mounts or even solid ones. I had a nasty miss once that didn't transmit like that.

 

I'm having the same problem but mine is instead of accelerating mine happens when I'm in 5th and let go of the gas, I feel the shifter shaking and the seat. What could it be please help

 

This is EXACTLY what I just encountered with my '98 Cobra. What turned out to be the culprit? Universal joint?