Foxbody Vibration At High Speed

[General karthief]

Don't cost a thing, and don't discount the bent axle neither, would it be possible for you to start the motor while you have it jacked up and place it in second gear and let the driveline spin and see if something is out of wack. This can be very dangerous, maybe ask someone to help you? Really need two people for that.

 

[Wetblanket]

That's what i thought you were saying.

that doesn't leave a lot for it to be. You have your wheels and tires balanced properly. It does the vibration no matter what gear your in starting at a certain speed, not engine rpm, that kind of takes out the worry of the pilot bearing. So transmission forward is ok and your wheels are ok. Not much left between those two points.

You have a tailshaft housing with its bushing and seal, the driveshaft with u-joints, and if you screwed with it, the pinion flange/pinion nut/crush sleeve and pinion gear. Did you take the pinion flange off for some reason?

As far as that goes, did you leave the rear end on the car during this?

When you dropped the transmission, did you install a new tailshaft housing seal and bushing? Like @90sickfox mentioned, this could produce a nice amount of vibration that would travel right through the new crossmember.

You said you had the driveshaft balanced and runout checked, right?

We really are getting past my limits knowledge here with this one. I suppose it's possible that some other thing just had bad timing to go out on you too, but i doubt it.

It just sounds like this would be in the driveshaft area of the driveline, from the ts housing to the pinion gear.

I'm going to invite a couple more people to your thread to see what they might know. @madmike1157 @Boosted92LX @hoopty5.0 @RangerJoe

should I rotate the ds into the holes that it was never in before the other pinion holes? I know it's been a while but I've had a bunch of stuff I've been doing

 

[Wetblanket]

Also someone told me not to long ago about the the new crossmember may have accidentally messed with the pinion angle if I get a newer crossmember will that do anything?

 

[General karthief]

should I rotate the ds into the holes that it was never in before the other pinion holes? I know it's been a while but I've had a bunch of stuff I've been doing

Just rotate the ds to the next hole that is used, I'm not sure the next hole will line up with the rest

Also someone told me not to long ago about the the new crossmember may have accidentally messed with the pinion angle if I get a newer crossmember will that do anything?

I don't know about that 'cause I don't know what crossmember you used, plus trans mount it is a possibility, can you contact the manufacturer of the crossmember? What trans mount did you use and ask the manufacturer of crossmember if its correct for their part.
Can you hold up your old crossmember to the replacement to compair? Maybe take a straight edge and compare bolt hole centerlines to trans mount pad.

 

[broncojunkie]

I'd like to follow along as I've been having the same issue. But I've replaced multiple parts with no change. (Note: most parts weren't changed to try and address the vibration, just for upgrades and general repairs). I've had 3 different t5's, new crossmember bushings/bolts (old ones were trashed), new transmission mount (polyurethane), switched to aluminum driveshaft, new flywheel, clutch, pressure plate, pilot bearing, throwout bearing, and I've re-indexed the shaft. Motor mounts are solid and in good condition.

It's worth noting that the vibration I'm feeling is pretty obviously NOT from a tire (which have also been replaced with a new matching, balanced set). It is a much higher rpm vibration than you'd get from a tire and (I presume) axel. I almost have to think the driveshaft is the culprit, although it does it with both the factory one as well as the aluminum one. The aluminum shaft is not brand new, but did come from another car that had no signs of vibration. U-joints were replaced just in case.

Another thing I tried....I added the weight to the tailshaft housing of the t5. I'm not sure if they all had them from the factory, but I had one lying around and threw it on just to see if I noticed a difference. No change.

Mine is noticeable starting at around 50 MPhil and gets progressively worse as speed increases. It is LESS noticeable when accelerating and MORE noticeable when letting off the gas and coasting.

 

[broncojunkie]

I'd like to follow along as I've been having the same issue. But I've replaced multiple parts with no change. (Note: most parts weren't changed to try and address the vibration, just for upgrades and general repairs). I've had 3 different t5's, new crossmember bushings/bolts (old ones were trashed), new transmission mount (polyurethane), switched to aluminum driveshaft, new flywheel, clutch, pressure plate, pilot bearing, throwout bearing, and I've re-indexed the shaft. Motor mounts are solid and in good condition.

It's worth noting that the vibration I'm feeling is pretty obviously NOT from a tire (which have also been replaced with a new matching, balanced set). It is a much higher rpm vibration than you'd get from a tire and (I presume) axel. I almost have to think the driveshaft is the culprit, although it does it with both the factory one as well as the aluminum one. The aluminum shaft is not brand new, but did come from another car that had no signs of vibration. U-joints were replaced just in case.

Another thing I tried....I added the weight to the tailshaft housing of the t5. I'm not sure if they all had them from the factory, but I had one lying around and threw it on just to see if I noticed a difference. No change.

Mine is noticeable starting at around 50 mph and gets progressively worse as speed increases. It is LESS noticeable when accelerating and MORE noticeable when letting off the gas and coasting.

 

[General karthief]

Replace the harmonic balancer?

 

[broncojunkie]

Replace the harmonic balancer?

I believe that would be rpm-dependent.