Gumby

Front end is all rebuilt, good alignment, July 4th night on a back country bumpy road suddenly anything over 55 has a strange vibration you can feel in the stick also.

Had the rears rebalanced, just did a test on the fronts with a diff set of rims n tires and its still there. I was almost sure it was a balance issue in the front.

Totaly lost where to look now.

Ta Re Ser

Sounds funny but if you have a steel drive shaft make sure you didn't throw a weight. Happen to me on a pick up once

sofakingdom

iTrader: (1)

Not too hard to tell the difference between a wheel-speed vibe and a drive-shaft-speed one:

Hmmmmm = drive shaft

Wubbawubbawubbawubba = wheel

Start there.

Assuming it's a wheel thing AT ALL, look for a bent axle or bent wheel; or even, a warped rotor. Those, the brakes will drag at one spot more than elsewhere, so it acts almost like somebody is tapping the brakes once every time the wheel goes around. VERY hard to tell the difference between that and some one of the other problems. One set of symptoms that points at brakes though, is if it's worse at some times than others, comes and goes for no apparent reason while driving down the highway, and changes right after it's been side-loaded (goes around a curve or the like).

B.A.M.F.88

Wheel bearings all good?

InfernalVortex

iTrader: (4)

I found a bent axle on mine. Didnt notice until I put my 17's on. It had been bent for YEARS and I just never go fast enough to notice. I had ar eally bad vibration above 70mph... barely noticeable at 60mph... but at 75 I had screws in my console vibrating themselves out.

I'd check bearings as well.

krazefbird

I would guess warped rotors on the front. If you did some heavy breaking after the front end rebuild and overheated the rotors, that would be it. Just a thought...

InfernalVortex

iTrader: (4)

Warped rotors are possible, but I would imagine if a front rotor was warped you'd see/feel the shaking in the steering wheel, and maybe in the pedal as well.

Bubbajones_ya

Another thing to check on the driveshaft would be the U-joints. When I had bad ujoints in my bronco, it made a slight vibration.

If you are under the car and jack it up enough, it would be easy to check the ujoints if you are checking the weights on the driveshaft too. You could unbolt the 4 bolts holding the shaft to the rear yoke and then move the front and rear joint around without pulling the shaft from the transmission.

Hopefully you find out what it is soon and good luck!

akanitro

iTrader: (2)

I had siMilan vibration concern. Had new u-joints installed and aluminum driveshaft balanced and now no vibration even at 130+

Gumby

Well info I found online said if its drive line it should do it at the same RPM in any gear. I can run up to 4000+ on take off and nothing, but over 55 it happens, clutch in or out, in N coasting or not. But I do feel the vibe into the stick and it does feel like right front.

I guess it could be a rotor, they were the cheaper ones as when I was chasing my brake problem, I had to elminate them, so I put on new pads n rotors and removed the crossed drilled n fancy pads.

I don't do allot of hard braking, I down shift down to 3rd when stopping.

krazefbird

I hear ya on the not so much hard braking as no one usually does unless they are road racing the car. But, all it takes is to get a rotor warmed up good and then go through a deep puddle or through the car wash, something that is going to cool the rotor quick and not let the metal cool down like it's supposed to. Mine were real bad, so bad that the car seemed sluggish on acceleration. I had to pop the brake pedal once or twice to get the pad/caliper to release right and then was fine. So got new pads and got the rotors ground/turned and was good to go. And yeah, I use the cheap pads too and bottom dollar rotors as well. I have no issues. But I would take the rotors off and have them checked and ground. Maybe new pads as well if they are worn unevenly.

InfernalVortex

iTrader: (4)

If it's the engine or pressure plate it will do it at the same RPM no matter the gear. Most parts in a manual will do it at the same RPM no matter what, but not always. Anything from the driveshaft back doesnt care about RPM, it cares about speed. So since it does it at a certain speed and doesnt care about RPM that just tells you it's not the engine and probably not the transmission.

I would put the rear axle on jackstands and then run it up to speed with the car stationary. That will tell you a lot. Be safe and chock the front wheels well. If it doesn't do it with the rear on jackstands it's probably in the front of the car. If it DOES do it on stands, then it's got to be in the back of the car.

krazefbird

[QUOTE=Gumby;5857807] I can run up to 4000+ on take off and nothing, but over 55 it happens, clutch in or out, in N coasting or not.

Your words right there say it all...clutch in or out, neutral coasting or not - no vibration unless over 55...therefore, I don't think u-joints, driveshaft, or engine issues. (Although I could be wrong - I am not a professional genius) but look for the simple stuff first - in this case you said right front, so right front rotor would be my guess.

I'm curious to know what you find!!

Gumby

monday I get the parts for my Buick so ill be able to park it again and look closer. Though I member again why the Firebird was such a nice car, with gas so cheap, I can drive for days n days and it cost little.

InfernalVortex

iTrader: (4)

If the driveshaft is out of balance it will vibrate as speed, and the driveshaft is part of the driveline. It's much more accurate to say that if it speed dependent and not RPM-dependent, then it's not the engine. It can still be the transmission or anything through the chain farther back, as the speed of revolution for most of those parts changes with speed. It's unlikely to be the trans since it's a manual, and most things in a manual turn with the engine, but not everything in it does.

Bubbajones_ya

I'm still thinking it may be the u-joints or drive shaft balance. Definitely check the front though if you think it may be coming from there, but if that checks out okay, I would check the shaft and joints next. I suppose I don't have the best guess though since I haven't experience the actual vibrations, but I had a similar situation with speed that turned out to be the U-joints.

Like what InternalVortex said, the rotation of the drive shaft is depend on the speed of the vehicle. Since it only happens 55+, it seems that the issue is also only speed dependent.

Now it could be a warped rotor or possibly even a bulging/damaged tire, but I also think those issues would be more noticeable in the steering wheel if they were on the front tires.

Anyways, good luck with finding it and hopefully it is a cheap fix!

krazefbird

ok, but wouldn't a driveshaft or u joint out of balance vibrate at any speed? Just more noticeable over 55? And since he said it came from the front, I would think that would rule out the drive shaft and u joints?

Bubbajones_ya

It could yes, but I think its also possible that a slight imbalanced shaft or messed up U-joint can vibrate at different speeds to.

Potentially, if the drive shaft threw a weight or something, it could introduce a new critical frequency of the system at a certain speed which in this case is around 55+. Now, if it were a new critical frequency that was introduced, the vibrations should stop if the speed changes a lot. So if he goes say, 75, it would probably disappear. Same thing could be said about the u-joints too.

Now if the vibrations continue at 55 even up to 75, then it may not be a critical frequency causing the issue.

I've had weird sounds and vibrations on my Bronco before, and I could have sworn they were from the front, but they ended up being elsewhere in the drive-line.

I definitely would check the front still if that's where it is seeming to come from, but if that checks out okay, checking the driveshaft would be my next move. It shouldn't be too hard to tell either with the rear jacked up, and the front choked.

InfernalVortex

iTrader: (4)

It would have resonant frequencies where the imbalance matched the natural damping of the other part sof the frame, suspension, and driveline and the amplitude of the vibration would increase.

It's very common for a driveshaft to vibrate in a 10-15mph window and then fade. Although that may not be the main resonant window, it could just be a harmonic of the resonant frequency.

Im not saying it's the driveshaft, just saying you cant rule it out. Put the rear on jackstands and run it up to speed and see what happens.

sofakingdom

iTrader: (1)

Which one have ya got? Doesn't make much sense trying to troubleshoot a wheel something if it's really a drive shaft something, or vice-versa.

Gotta know what part of the car is farkled before you can fix it. At least, what SECTION to look in.

Gumby

been to dam cold n I just got a stone drive way to work on.

krazefbird

Any Luck?

Gumby

Still dunno, just yesterday the last of the 3in of ice behind it melted, the ground is soggy wet. [ was nearly burried in snow not long ago, up to the top of the doors ]

Gumby

Finally able to get it out, but only for a drive, still there, I can yank the wheel side to side hard at speed and its beyond responsive, not a hint of slop, like its glued to rails.

still deff comin from the right front area. still only happens over 50 comes in good at 55+. RPM don't matter. still felt it up to 70+

Need things to dry out a bit more then ill yank the wheel off and look more, eyeball the rotor.

ground will be to soft for a while to get a jack under it to get it up high enough to inspect the shaft.

krazefbird

I know you said not the tires but I would double check, maybe out of balance? Maybe there is something on the tire itself causing it? Otherwise possible alignment issue? Tie rod? I got no idea otherwise!!

John in RI

iTrader: (167)

Sure it's not a tire ?? ( just pulled this off my 95 ! )



Many times a bad tire can't be seen by eye at first & not all tire failures are as significant as the one I had on my Z last week !! When that tire failed ( front end ) I started getting a minor vibration but the tire looked fine. But, as I continued to drive the car the vibration continued to get worse. ( then it just gave out all-together !)

All joking aside,..... once you can lift the front end you'll KNOW much more than just how it feels when driving. After grabbing the raised wheel @ the front / back you'll know if the steering linkages are loose, after sticking a pry bar under the lifted tire and prying UP you'll know if there is any play in the Ball joint, and after spinning the wheel you'll know if the bearings are OK. If those 3 things appear fine then I'd remove the wheel and check the tire for defects and balance.

Bob88GTA

iTrader: (2)

!!!!!!!!!

That don't look good John! Put the bad side down!

John in RI

iTrader: (167)

That one might be ugly,..... but at least it wasn't SCARY !!

This is the one the blew out @ 125 on the 5-6 upshift about 2 months ago: ( I think it was an 'H' rated tire )




That,........ Was scary ! Even this tire seemed "perfectly fine" before it failed.


P.S. When ever possible the FIRST thing I try to do when I try to find a vibration is to swap wheel(s). A wheel &/or tire is almost always responsible unless there was. It's pretty easy to find slop/slack in the front end, but no possible to "see" a wheel/tire defect.

Gumby

I rebuilt the front end not long ago, it was fine after that, it happend suddenly on back coutry road on 4th of july, I have put a different set of rims and tires onthe front and it was still there.

Gumby

near 70 yesterday, woke up to snow and slush, spring can be curel, as I just got stone drive way outside to work on.

jmd

iTrader: (4)

You feel it's at the right front.

Get things in the air and spin the tire. There may be run-out that's not as bad as John's, but enough to cause a vibration. Even the new ones I just got late last year aren't all that great, but in comparison to one I have that lost it's weights, they're grand.

Also, a device that measures the frequency of vibration would potentially be helpful. There's a phone app oscilloscope that tells you the kHz(?) and if it's between like 10 or 13 k at 60mph, it's a tire, a few times higher than that would tend to be driveline. It's not perfect, but it's basically free and my weight-less wheel showed up exactly as I expected.

Gumby

Ive had that app but how does that work? hold it in hand, lay on seat, floor?

how smooth does the road need to be? most are still full of buckles from the freeze thaw of winter.

Gumby

Well I can say I check more stuff today, all I can find is the rotor does drag a bit more in a spot then other, when I spin it by hand.

Gonna get an earlier start tomorrow n just change it, only $25 for an autozone special.

Bob88GTA

iTrader: (2)

Just a suggestion...get new inner/outer bearings and seal while your there. The new rotor will have the new races already in. No sense in using old bearings on the new races. JMO

Gumby

Well its not the rotor, ao I pulled the shaft and the Ujoints are all tight, only place I find any slop is the output shaft.

Google search "T5 output shaft slop" finds 999 questions and nearly all of them say its normal.

not my vid, but same thing, as his was a new tranny
https://www.youtube.com/watch?v=87VhntVzOAE