Bad vibration at 80+ mph

go-stang5.0 · Jan 24, 2007

Im getting a vibration in the trans tunnel area and it starts at about 75mph and gets really bad above that (feel it in the trans tunnel and shifter). I know ist not rpm reated as it onl happens at this speedand above. Shifted from 5th gear, 4th gear, neutral, and at this speed and it does not change the vibration. I have since replaced the axels and a rear wheel (curbing incedent) and everything in the pumpkin looks fine. So unless I missed anything, its gotta be the output saft on the tranny or the DS. I checked the u joints on the DS and they seem fine (I didnt remove DS from car, jus wiggled it) and I feel 2 weights on it and cannt find a weld where a weight might be missing. This is a FMS alum. piece. Anyone have any ideas? Also this happend on the highway at 150+ mph. Everything was fine and then I heard a clunk underneath and things started rattling like crazy. I immediately pulled it down to about 55mph and it was fine again. But since then I cant get it over 80 without the bad vibes. Any thoughts? -Robin

go-stang5.0 · Jan 24, 2007

Oh and there are no abnormal noises from the tranny.

VibrantRedGT · Jan 24, 2007

Had the same issue. Replace the driveshaft with an aluminum one.

Bosko5.0 · Jan 24, 2007

where the driveshaft connects to the input shaft on the front there is a rubber ring like the harmonic dampner since the car is old it could be coming apart just like when it happens to the dampner which means it rotates some which causes the balance to be off.

i took a pic of it but camera died right there after.

go-stang5.0 · Jan 24, 2007

I do have an aluminum one vibe. Well, you obviously werent reading my post.

A rubber thingy? I thought it was just the u-joint and the slip yoke that went right into the output shaft of the tranny? I'll have to look see tomorrow morning. Any other ideas...keep em coming.

go-stang5.0 · Jan 24, 2007

So far it looks like everyone says driveshaft....thats good. I'm a happy camper as long as i dont have to pull the tranny.

HISSIN50 · Jan 24, 2007

Did you also check the wheels for missing weights?

I still kinda like the DS possibility - it's too bad it's such a pain to get them dynamically balanced.

Do you have a buddy with an alum DS? He could let you swap it onto your ride for a test drive.

Good luck.

go-stang5.0 · Jan 24, 2007

I still have the stocker, I bought the car w/ the aluminum DS installed but since the previous owner didnt throw it out (and gave it to me with the purchase of the car) I'm assuming its still good...so maybe I'll try that (gotta go rummaging thru the shed ). And no it wasnt a missing wheel weight. Well, I did throw some wights on a wheel (first thing I checked) and had it rebalanced and checked the other wheels however that made no differece in this problem.

1TallMF · Jan 25, 2007

Bosko5.0 said:
where the driveshaft connects to the input shaft on the front there is a rubber ring like the harmonic dampner since the car is old it could be coming apart just like when it happens to the dampner which means it rotates some which causes the balance to be off.

i took a pic of it but camera died right there after.

I'd like to know more about this as well. The only other peice that I'm aware of is the tailshaft bushing, which is metal. I've got the same problem but with a stock driveshaft. Aluminum one is coming as soon as it gets warm enough to work on the car.

1bad04GT · Jan 25, 2007

same problem here with stock ds. extremely interested

go-stang5.0 · Jan 25, 2007

I called 2 shops and both think its a ujoint. I was told remove it amd move it thru a full range of motion to check not only for play but binding/seizing. Im gonna pull it out now and see what I can see.

go-stang5.0 · Jan 25, 2007

For those who care, I just removed the DS and I did indeed throw a weight off of it. Now I gotta find a place that will balance thje fu*ker.

HISSIN50 · Jan 25, 2007

Glad to hear that you found it. I personally think a dynamic balance is kind of neat if you can find a driveline shop to do it (they balance the entire rotating driveline assembly, not just the DS itself). The rest of the driveline can be a little off (at the factory, the components are loosely balanced as a whole), so even a perfect DS can result is slight vibes (and I don't mean Joe's kids ).

Again, nice work tracking it down - that's half the battle.

Good luck.

VibrantRedGT · Jan 25, 2007

HISSIN50 said:
the components are loosely balanced as a whole), so even a perfect DS can result is slight vibes (and I don't mean Joe's kids ).

Again, nice work tracking it down - that's half the battle.

Good luck.

I'm glad you specified that.

5.0_GT_kid · Jan 25, 2007

I had this same problem...my U-joints were bad.

go-stang5.0 · Jan 26, 2007

Well got the DS balanced yesterday (not dynamically) but hey it will have to do. Havent had the car on the highway yet so I cant really compare this balance vs. the ford balance (before I thru the weight) but I think it will be fine. I'll post back when I drive the car and get some speed going on it. Thanks for the help.

Donny · Jan 27, 2007

Hopefully that will fix your problem but I was going to say I had a similar problem and it turned out that one of my rear tires was causing it.

go-stang5.0 · Jan 31, 2007

Anyone who cares, yep the balance fixed the prob. Thing is the place did not have a TIG or aluminum weights. So we balanced it with steel weights, drilled it out (the weight and DS) and pop rivited the weight in. THey said thats how they do all the driveshafts and havent had a problem yet. My only other option that would tig a weight on was a place 50mi. away (this place was like 5 mi.) so thats that. I know its too late now but I dont think it will be a problem, do you? I think I'm gonna go measure the diameter of the driveshaft and find the angular force on that rivet @ 170 mph, then try and find a load rating for the rivet.

Bosko5.0 · Feb 1, 2007

i think it should hold but you could try and figure all the calc. out but.......

glad you fixed it.

1TallMF · Feb 1, 2007

If you don't mind me asking, how much did the ballancing set you back? I was always under the impression that the cost was close to what a new driveshaft would be.

Bad vibration at 80+ mph

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