Foxbody Vibration At High Speed

Wetblanket · Dec 16, 2016

So this is my third post about this and I haven't fixed it yet. After a clutch job two summers ago I've had this horrible vibration at high speed not rpm dependent just speed dependent. We bought the flywheel from oreilys we changed everything but we did not change the pilot bearing or atleast I'm pretty sure we didn't I can't really remember. We also changed the crossmember to the ford performance one. This vibration starts at 50 or so and get progressively worse. It feels like it's just gonna come apart it does it when rolling down hill too. I've already had my ujoints done by a shop and a rebalancing on my aluminum driveshaft. I already have the aluminum driveshaft I have my wheels balanced because people always say those two things. I'm lost I have no clue what to look for or anything. This is driving me insane I'll honostly do anything for someone to tell me the fix to the problem. This was after my clutch job but I thought if say the flywheel was out of balance or the pilot bearing was bad it would be rpm dependent not speed in probaly wrong I don't know. If someone can please help me that would be great. It drove fine before the clutch job so it shouldn't have anything to do with the axles cause we didn't touch those

jrichker · Dec 16, 2016

The driveshaft has a yellow dab of paint on the rear u Joint flange. The rear axle flange has a matching dab of paint. Those are alignment marks and they are supposed to be lined up so that they are right together. Misalign them and you will get vibrations.

General karthief · Dec 16, 2016

A couple questions
When it starts to vibrate, does it go away when you push the clutch in? (leaving it in gear)
At speed when its out of gear, clutch released
Did you rev the engine up to the rpm where it would be at speed where it would vibrate

Wetblanket · Dec 16, 2016

karthief said:
A couple questions
When it starts to vibrate, does it go away when you push the clutch in? (leaving it in gear)
At speed when its out of gear, clutch released
Did you rev the engine up to the rpm where it would be at speed where it would vibrate

It still vibrates when the clutch is pushed in at gear at 1k rpm and I'm going right now to test and see if it does it when at high rpm when not in gear but rolling I'll let you know

Wetblanket · Dec 16, 2016

karthief said:
A couple questions
When it starts to vibrate, does it go away when you push the clutch in? (leaving it in gear)
At speed when its out of gear, clutch released
Did you rev the engine up to the rpm where it would be at speed where it would vibrate

So I just tested it it kind of of vibrates when you rev it out of gear like you said but it doesn't feel like it does when you're going 70 it's just minor but you can definitely feel it

General karthief · Dec 16, 2016

Lets backup a second
Wheels balanced check
Driveshaft balanced check
Vibration check
Now if I read correctly you stated a slight vibration when you rev the engine. If you were siting still when you did that and have a vibration and you didn't have the vibration before the clutch change it is likely a balance problem with the clutch assembly and/or flywheel.
If this is accurate than I think you got the wrong flywheel, first check the part number on the recite for the flywheel they may have given you the wrong flywheel or the wrong flywheel got put in the box.

General karthief · Dec 16, 2016

jrichker said:
The driveshaft has a yellow dab of paint on the rear u Joint flange. The rear axle flange has a matching dab of paint. Those are alignment marks and they are supposed to be lined up so that they are right together. Misalign them and you will get vibrations.

Would that be relavent if he has an aluminum driveshaft?

Wetblanket · Dec 16, 2016

karthief said:
Lets backup a second
Wheels balanced check
Driveshaft balanced check
Vibration check
Now if I read correctly you stated a slight vibration when you rev the engine. If you were siting still when you did that and have a vibration and you didn't have the vibration before the clutch change it is likely a balance problem with the clutch assembly and/or flywheel.
If this is accurate than I think you got the wrong flywheel, first check the part number on the recite for the flywheel they may have given you the wrong flywheel or the wrong flywheel got put in the box.

The vibration from revving isn't bad at all it's probaly just my motor mounts and it's only at like 5k rpm so it's not that while driving it has to be high speed that's why I'm so lost

jrichker · Dec 16, 2016

If I remember correctly, my aluminum driveshaft has the paint dab, but it was manufactured sometime between 2000-2004..

General karthief · Dec 16, 2016

That would apply to factory shafts, not aftermarket?

Wetblanket · Dec 16, 2016

There is also a clunk sometime when putting it into second from first or reverse to first idk if this will help

General karthief · Dec 16, 2016

Wetblanket said:
The vibration from revving isn't bad at all it's probaly just my motor mounts and it's only at like 5k rpm so it's not that while driving it has to be high speed that's why I'm so lost

I think you have a balance problem in the clutch/flywheel area
You should have no vibration at all, a slight vibration when revving the engine out of gear, sitting still is an indication that makes me believe the clutch/flywheel is the problem, a slight vibration 'free revving' is going to be worse when in gear and driving down the road.
Thats just my opinion/experience from what I have read on this post, I don't know what engine trans combo or vehicle year and modifications if any.
There are two different 302 ci engines that have two different flywheel balances, one way to tell is firing order, but your problem I believe will be clutch/flywheel related because thats the only thing you say was changed when vibration started.

General karthief · Dec 16, 2016

Wetblanket said:
There is also a clunk sometime when putting it into second from first or reverse to first idk if this will help

That will just confuse me, did it do that before the clutch change?

General karthief · Dec 16, 2016

Part number for crossmember please.
And transmount
They where changed same time as clutch right?

Wetblanket · Dec 16, 2016

karthief said:
Part number for crossmember please.
And transmount
They where changed same time as clutch right?

Yes crossmember is https://lmr.com/item/M5059/82-93-Mustang-FRPP-Adjustable-Trans-Crossmember and transmount is https://lmr.com/item/LRS-6068A/79-98-Ford-Mustang-Transmission-Mount. Also the clink started after I took my ds to the shop and got u joints and balance.

General karthief · Dec 16, 2016

First, I don't think your trans mount/crossmember is a problem as long as it was a bolt in affair.
Did you mark your driveshaft/flange and pinion flange so it could be bolted back together in the same place? I have been told this makes no difference when replacing ujoints but I do it every time I remove the shaft from the rear end flange regardless of joint replacement. If you didn't mark the orientation of the shaft/flange you may try to unbolt it and rotate it one bolt hole at a time amd see if it makes a difference.
I still lean towards the clutch/flywheel, rotate the driveshaft a couple times one bolt hole at a time, it costs nothing and may fix it.

Wetblanket · Dec 16, 2016

karthief said:
First, I don't think your trans mount/crossmember is a problem as long as it was a bolt in affair.
Did you mark your driveshaft/flange and pinion flange so it could be bolted back together in the same place? I have been told this makes no difference when replacing ujoints but I do it every time I remove the shaft from the rear end flange regardless of joint replacement. If you didn't mark the orientation of the shaft/flange you may try to unbolt it and rotate it one bolt hole at a time amd see if it makes a difference.
I still lean towards the clutch/flywheel, rotate the driveshaft a couple times one bolt hole at a time, it costs nothing and may fix it.

Alright I'll try and do that tommorow this vibration is gonna drive me insane

RaggedGT · Dec 16, 2016

I'm with @karthief - the clutch/fly wheel is where I would start

General karthief · Dec 16, 2016

RaggedGT said:
I'm with @karthief - the clutch/fly wheel is where I would start

You may regret that, I'm not the sharpest knife in the drawer,
Bbbuuuttt, I'd bet he got the wrong flywheel.

90sickfox · Dec 16, 2016

Where do you feel it the most...center console...rear of car...steering wheel ? I've seen some weird stuff in my years as a technician. Sometimes tires can have imperfections in the radial belt that can cause vibrations at speeds over 45mph. The only way to find out is with a road force balance. All shops don't have that type of balancer but it is the best. I've had instances where the tires have balanced to zero with a conventional balance but the customer still had vibration issues. Once we put it on the road force balancer we found we had to rotate the tire on the rim in order to counter out of roundness in the tire.

The issue with conventional tire balancers is they don't simulate load on the wheel. The road force machines actually put a load on the rim and tire and measure the weight and how far out of round the wheel tire combo is.

Like every one else has said...including you. If it started when the clutch was done then it probably has something to do with that. If it doesn't change in or out of gear...or on or off the gas...then you can almost cancel out the trans and rear. Axles and flanges can also bend causing vibrations that don't change except for speed.

at 50mph you're not spinning the motor at 5000rpm. at 50mph you should be somewhere around 2000rpm. Load is load and rpm is rpm. So, 2000 rpm in 3rd gear is like 2000rpm in 4th and 5th. The wrong flywheel will shake the teeth out of your mouth at the same rpm.

I had a car that had a broken factory plastic fan blade. That thing shook worse than a misfire and solid motor mounts. Check the fan blades. While jacking letting the motor tilt back to remove the trans its pretty easy to hit the shroud and crack a fan blade... Trust me...I've been there and done that.

Foxbody Vibration At High Speed

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