Its been awhile since I've posted...lifes had me busy but alas, I've found myself working on the T-bird again. To update I put a 8.8 from a auto TC in the car along with Steeda lowering springs and CHE adjustable lower control arms. After that the car developed a healthy vibration. This only occurs at certain speeds when you let out of the accelerator and/or get back into it and also when you get to higher speeds. I assumed (and had a Ford mechanic friend look at the car) that the pinion angle was way off due to the lowering springs and other changes. I just installed the adjustable upper CHE control arms and took my first drive after adjusting the pinion angle downward...I still have a pretty serious vibration. But now it seems to occur sooner and is a little worse at higher speeds. Obviously I still need to adjust things but I'm concerned it still won't take it all the way out. Previous to this I also lowered the trans crossmember to try and help. Just wondering if anyone has had this problem and how you solved it? Who knows maybe if I simply adjust a little more it will take the vibration out...
On a side note I was impressed on how the control arms improved the ride and handling. A nice little bonus!
I hate trying to get pinion set!
But frist check driveshaft and make sure U joints are all good and its bolted to rearend right.
After that you can redo pinion angle.
Here are tips to doing it right.
Using a gravity angle gauge (Available at hardware stores) to measure the angle between the driveshaft and the ground & the pinion and the ground.
Hold the gauge on the bottom of the driveshaft. Align the gauge front-to-back under the car in line with the driveshaft and read the number from the gauge (Note if angle is up{+} or down{-}). Write down this number.
Next, hold the side of the gauge against the front of the pinion (beside the driveshaft). Write down this number (Note if angle is up{+} or down{-}). Subtract the first number from the second number. This is your pinion angle
Mounts change the degree's
All solid mounting points. -1 to -1.5
Half Solid & Half Poly Mounting points -1.5- to -2.5
All Poly mounting points -2.5 to -3.5
All Rubber mounting points -3 to -4.5
The more you get away from having all solid mounting points the more the rearend is going to try and rotate upward during launch. Therefore the more angle you must start with to prevent the angle from becoming positive (+). The idea is that when the rearend rotates you want the angle between the driveshaft and the pinion would be 0.
Wow thanks man...I will have to work on the car more this weekend. I've spent the last two nights putting the control arms in and working on trying to adjust a little at a time. That gets old; jack car up, adjust arms, drive, repeat. I was getting more than a little frustrated last night.
This should help!
I put all new U-joints in a while back so that should not be an issue...
Totally unscientific input, but when I replaced a soggy oil drenched tranny mount with a new mount (which raised the tailshaft), my vibration levels were reduced significantly. I added some washers to raise it some more and that helped too.
So I've adjusted under the arms several times and never did get it just right. I still had a slight vibration. The last time I was under it I forgot I had it in neutral and the car rolled into my garage door and put a dent in the fender. All these years of babying the car only to do that...man was I pissed.
I think I'm going to take it somewhere where they have a nice lift and let them do it. Thus far I've done most of the work on the car but I've had enough of this pinion angle !!
Once this issue is ironed out and I fix a couple of small oil leaks (rear main, valve covers, etc.) i think I'm going to look into getting the car painted.
Sorry to resurrect one of my old posts. I ended up taking the car to a friend of mine who does rear end work this summer. He adjusted my pinion angle and readjusted the backlash on my 8.8. Once I got it back there is still the same vibration (though not as bad). Couple of questions:
1.) Could a broken motor mount cause a vibration that sounds like it is coming from the rear of the car? I know for sure I have a broken one right now and I guess the sound could travel.
2.) Since the car has the original driveshaft and different rear end should I consider having the driveshaft balanced?
So far I have had the wheels/tires rebalanced, the pinion angle/backlash reset, and new u-joints. I freakin' hate trying to figure this kinda stuff out. Its starting to get expensive too.
Does the vibration occur at a specific RPM? if so your drive shaft is probably out of balance. Also is the dampener on the end of the transmission slip yoke still there? It's a big round donut you can't miss it. If you'd like I can send you a picture of my drive shaft without one. (Don't ask)
From what you described, it sounds like what happened with my TC.
The pinion bearing developed play, and would vibrate, but would vibrate worse if you didn't have a load on the car, like coasting downhill in neutral.
Eventually the pinion bearing exploded at 85mph because the rear had a very slow leak I never noticed.
I was gonna say it's the pinion bearings not the pinion angle.
Replace all the rear end bearings any get pinion bearing preload right
Try a hose clamp on the drive shaft, rotate it a 1/4 turn at a time, see if it gets worst or better. a simple but effective way of checking ds balance. It worked for me I had a vibe at about 70.
actually its still on, Had it with my stock setup and my new one.
I have a aluminum ds to put on someday.
I'm fairly confident its not the pinion bearning. The guy that was in the rearend the last time said it checked out fine.
It does it around 70-75 mph and gets worse the faster you go. And it will also come and go as you get in/out of the throttle. I'm gonna crawl under the car this weekend and check for the exhaust rubbing anywhere...who knows it could be something that simple.
It seems to be more speed specific than RPM specific. The dampener is still there.
Get a carbon-fibre driveshaft - a tiny bit expensive (lol) but it solves all the vibration problems!
lol. yeah I should get a carbon fiber driveshaft...and a '03 Terminator Cobra motor and 6 spd while I'm at it too. lol. I think that would break the budget, but at this pace I will have more than the cost of a carbon fiber driveshaft in figuring it out!!!
What sux is I can't really drive the car to tweak and test...stupid winter time.
Somehow I got in on a group buy for PST carbon fiber driveshafts on a Mustang site - it's definitely nice :D
I bet...if you don't mind me asking what kind of $$$ are those puppies?
Heh, you don't want to know!
Off the shelf Mustang is $585, custom length (like ours) - maybe $700?
I got mine for like $439 IIRC - a very good deal!
http://www.pstds.com/carbonfiber.htm
:punchballs:Resurrecting this thread again. I am still fighting this darn vibration. Today I took the driveshaft to a driveline place and they checked it for balance for me. They said it is balanced perfectly.
So far I have changed:
1.) all new bearings in rearend (totally rebuilt, even has a new carrier)
2.) adjusted pinion angle to within spec with CHE adjustable UCA's
3.) new Chuck W motor mounts
4.) rebalanced all wheels/tires
5.) new front wheel bearings
6.) all the exhaust components have been changed while the vibration has been going on and nothing has changed, so I am confident there is no rubbing
7.) driveshaft checked for balance
8.) new u-joints
I'm really about ready to go nuts with this guys! As I stated before, the vibration starts around 70 mph or so and gets worse with higher speeds and started after I put in the 8.8 and lowering springs. Anyone want to throw some ideas at me?? Would it matter how the driveshaft is clocked when bolted to the rear? Obviously this is not the original rear so could there be some sort of imbalance between the two? Could the tranny somehow be causing a vibration like this??
HELP!:dunno:
It may be the angle of the input shaft of the driveshaft into the trans. If the angle there is too sharp it will cause a vibration.
I had a vibration after swaping out a T5 for a T56. The tail of the trans was too close to the floor. I drilled holes in the crossmeber below the stock one's, made a dramatic difference.
I had the same thing happen on my Mustang when I installed drop motor mounts.
Mark
LOL. I already drilled holes in the trans crossmember and dropped it as part of my pinion angle experiment.
I have read on Corral forums about some people going to a aluminum driveshaft and curing this problem. Something about critical speed of a steel driveshaft after changing rearend gears?
I have the same problem but mine was a shiznitty gear change, (I hope) I chased everything also I have had the problem for over a year still gathering parts to fix it.new gears, spool, axles, and c clip eliminators. I hope that this fixes the problem.
I am on year 6 of my vibration. I don't drive the car much but want to drive it more...I'm just afraid too go any distance due to the vibration. I am so close to having this car where I want it...:toilet:
My vibration problem went away after the aluminum drive shaft was installed by me.After the gear swap,vibrations were normal,now,no more of them.
did you do the aerostar shaft or the crown vic?
Crown Vic.It was free.I sent the yoke,,and drive shaft to Performance Driveline in Oklahoma City (shipping was only like $22.00 or so),and they cut it,welded it,installed the correct yoke and I sent with new adapter u-joints,balanced it,and sent it back.I sent it on Monday around 4:00,and at 3:00 Tuesday,they called and said it was ready.Awesome guys.
what yoke did you use
I would borrow or swap tires with someone. I had a horrible vibration through two sets of tires on my wifes neon. Had the tires re-balanced many times and couldn't get rid of it. Ended up getting a flat tire and threw the mini-spare on, and no vibrations. You could not tell the tire was damaged.
I dropped the driveshaft on my car when my front u-joint broke. Put a couple of dents in it and grinded the end on the ground untill I came to a stop from about 65mph. I have a slight vibration, but I think it is my front brakes being warped so bad. My vibration remains constant and is noticeable from 35 mph up. All the brakes for our cars are now made in china. I drive anywhere from 55-85mph every day and drive about 150 miles a day, mostly freeway.
I don't think the driveshaft is as critical as people make it out to be. It only turns about 1/3 the speed that the rear end does, depending on your rear end. I would really swap out the tires/rims before I ponied up for a aluminum driveshaft. It is something I want to eventually do though.
I have aluminium driveshafts in both cars and had them both balanced prior to adjusting the crossmember on the T-Bird (on the Mustang I replaced the drop mounts w/standard height mounts).
Chasing an aluminium draftshaft is a red hearing, the material of the driveshaft is irrelevant.
Isolating each component in a process of elimination is necessary. With the car on a lift or jack stands, start pulling off or disconnecting one item at a time. You've replaced lots of parts, it's got to be something simple. You'll find it and probably wonder how you missed it...
Good luck.
One from an '88 Bird.I had an extra yoke and in the garage,and that's what I sent them.I removed the Crown Vic yoke and to save on shipping charges.They are probably as heavy as the shaft itself.With shipping and all,I'm probably into the drive shaft for less than $140.00.Pretty fair to me.I've always been taught that the aluminum drive shaft transmits less vibration that the steel one,and by the cast amount of Stang owners (and myself) who have also had great results from using an aluminum piece,I would agree.
to the OP: can you swap axles to see if one (or both) may be bent?
Thunderjet302 had a bent axle once....
Just thought you might find this an interesting read since the OP brought it up:
http://www.tccoa.com/articles/tranny/transmission/page17.shtml
Darren
I am 99% sure that the last guy that worked on the rearend for me checked the axles. Maybe I need to recheck them.
I think that the material of the driveshaft can be important due to its mass when changing to 3.73 gears or higher...at least that's how I understand it.
You've got it right though...it has to be something simple!
Yep passenger side. I replaced the axle and the vibration went away.
I have a factory driveshaft and 3.73 gears. I have no noticeable vibrations at highway speed (I did have it rebalanced). I have a slight vibration between 73-77 mph on the highway that feels like driving over rumble strips but I know it's the road surface. How do I know? Every other car I've driven over the same stretch of road has the same vibration at those speeds:hick:
With a drive line vibration issue, checking the shaft for balance illiminates it from the diagnostic process. Aluminium or steel, makes little difference.
If the desire is to replace the shaft w/aluminium as an upgrade & added expense, great.
If the steel one is balanced, replacing it with aluminium won't get rid of the shake, something else is going on.
I'm good with that.I still like the aluminum shaft a lot,and,it wasn't much.I spent about,or less,than $140.00.
In regards to the driveshaft...is there anyone near you that has a Bird/Cat? If you could borrow another 'shaft for a few minutes, it may rule out yours being out-of-balance...
In my area seeing a fox t-bird/cougar is like seeing a unicorn these days. Most of the white trash folks have ragged them out by now.
I guess Mercuryman is the closest to me or maybe Chuck W but I doubt if they would let me "steal" their driveshafts. Especially since I have never actually met either one of them.
That is a good idea though.
If you were out here I would let you borrow mine. I am sure someone has a stock driveshaft in your area laying around.
Are you absolutely sure its coming from the rear and its not due to the front end being out of alignment?
Car has had the front end aligned twice since I've had a vibration. The 1st time was when i put the lowering springs in back on 2005, 2nd time was when I installed the Mustang front brakes a year or two ago.
I've gone over the front end and everything seems solid.:dunno:
A bad front end alignment won't cause a speed sensitive vibration.
K well i was just wondering cause i have almost exactly the same problem but i know my front wheels are about 2" out of alignment with each other.
I had a BAD vibration in my '86 (when I had it). When I would let off of the throttle the vibration would show its ugly head. I replaced the u-joints on the driveshaft and it all went away.
I am still fighting this vibration and would appreciate any ideas you guys could throw at me. Its not noticable at speeds under 60 (where I do most of my driving) but rears its head the faster you go. At 70-80 mph its really bad. It is not RPM related at all, all speed related. It definately seems to come from the rear of the car.
Just to recap, the vibration started after I swapped to a junkyard TC 8.8 rear, changed springs, and added CHE control arms (this was done all at once). It has the brake rotors that came with the axle but I had them "turned" at my local NAPA.
I have done the following since the vibration started (some to try and cure the vibration, others just mods):
1.) rearend completely rebuild, every bearing, etc
2.) trans has been recently changed to T5 from AOD (including crossmember, trans mount, etc)
3.) new motor mounts
4.) tires rebalanced twice
5.) exhaust changed
6.) added CHE adjustable upper control arms and set pinion angle (I have had two shops go through the rear axle, one guy specializes in drag car/race car rearends and could find nothing wrong with the axle)
7.) changed u-joints
8.) cussed, stomped feet, turned red, hit things, etc
9.) took driveshaft to driveline specialty shop and had them check balance...balanced out 100% perfect
So I am at a loss...I've read that the two most common speed-related vibration problems are 1.) tires or 2.) warped/bad brake rotors. As mentioned earlier, I had the original TC brake rotors "turned" when I swapped in the axle. Could these be warped or somehow messed up enough to cause a vibration as described??
HELP ME!!! lol.
Did you swap the axles? Maybe one has a super slight bend in it......just enough to cause a vibration.
No vinnie I have not swapped them. Supposedly the guys that checked out the rearend made sure they were "true", but like you said it could be just very slight. It would not take much to get a vibration.
This is making me want to swap back in the stock 7.5 rearend, springs, and control arms. I HATE this vibration. If I ever figure it out, I'm gonna throw a party to celebrate.
Did you try clocking the DS every 90 degrees? Get a 1" dial indicator with a magnetic base and you can check the run out on the axles at the back of the . If you need I can sketch up how to do this and post it.
Darren
Try swapping just the axles. I believe they're the same.
Pull the 7.5" axles and measure them from the end of the splined end to the wheel side of the axle and post that. Someone should be able to verify if the TC rear axles are the same length.
Darren
Man I feel your pain I too am dealing with the same problem all new suspension, drive line new u joints and balanced, rebuilt trans, new axel bearings,had a shop align and set pinion angle, and still have same vibration I have all new wheels and tires on order to see if that helps
Good read not that it will solve your problem but it has some good basic understanding of how the geometry works:
http://www.drivelinespecialist.com/Tech1.htm
I battled bad vibration in my Bird for years and I finally got rid of it when the valve in the driver side AFR 185 dropped into the #7 cylinder...problem solved. Hopefully with this new build I won't have to battle it again as it sucked to drive the car and it stayed parked most of the time because of it. Mine was cyclic and is what most call a sympathetic vibration due to the cyclic nature. Anyhow, stick with it and quit throwing money at it. Make a list of all the things you have tried and what else you can do that is free. One question I do have is when you are at speed and you put it in neutral does it go away? What about neutral and the clutch engaged? Doing this eliminates everything upstream of the transmission output shaft. If the only thing you changed was the rear end then it is definitely between the drive shaft and the axles of the rear end. Pay very close attention to the angles of the two u-joints as they should be equal in degrees but no less than 1 degree and too much of a degree will also do bad things. Read the article that I have listed here and the one I posted last year and make sure you understand them.
Also, I am going to have to call bullshiznit on the DS material not doing anything with vibrations and once you balance a steel DS then you should eliminate it from the equation. Can balancing a steel DS solve some vibration issues? Sure it can but its not the cure for all vibrations and this also holds true for an aluminum DS as they are not the one and done answer either. Different metals have different harmonic properties. Steel and aluminum translate vibrations and very differently hence all of the people who have switched to an aluminum DS when going to numerically higher gears and resolving the vibration issue. Read the article by the Ford driveline engineer that I posted in this thread last year and he explains and proves this very fact. All I am doing is randomly regurgitating what he presents in a very well written article.
Darren
Thanks for all the ideas, fellas.
I would have guessed that the 7.5 axles are the same length, but would a 7.5 axleshaft have a different amount of splines than an 8.8(I have no idea)?? The old 7.5 axle is just laying in my Dad's barn, so this may be worth a try.
At this point, I really can't remember if I tried reclocking the DS. But I will definately put that on my to-do list for this weekend. I assume to check the runout you just turn the axle and use the dial indicator to measure any change on the ?
If you put it in neutral or push in the clutch, the vibration is the same.
Thanks again guys...
Spline count should be 28. The four cylinder Fox Mustangs have 7.5's and the Fox 5.0 cars have the 8.8's but the axles are identicle so one would hope Ford would do the same thing with the Birds. The neutral thing just firms up my theory that its DS to axle related which is pretty much what everyone else is saying. You are dead on with your dial indicator on the axle description. I would do this before I started clocking the DS as that is a pain in the rear where the run out is pretty easy to do. Good luck man and hopefully you can get this sorted out tomorrow or Saturday and enjoy the weekend.
Darren
I'm betting the passenger side axle.
I hope that's what it is, hell if the axles are the same from 7.5 to 8.8, I might as well swap them just to elimated that from the possible causes. All it would cost me would be some gear oil and some time.
You have the 86-88 TBird 7.5...which is the wider housing. The axles are not the same. The length is the same, but the bearing surfaces are not.
However, you MAY be able to use them in the narrower housing if you can verify that you have enough bearing surface on the axle to account for the difference. You would need at least 3/4" more bearing surface INBOARD on the 7.5 axle for it to work in your 8.8.
I don't know if this helps but since changing my axles, spool, and gears I am vibration free.... sort of I think the vibration I had before caused my tranny to fail so now that I fixed the rear end I now have a new vibration at 110mph, before it was 65mph and and I thought my car was going to blow up, if I throw it into neutral the vibration stops. I know you might not want to hear this but you gears might be setup wrong, I was almost ready to change out my complete rear end because no matter what I bought for it I could not fix it, I did upper and lower double adj. control arms, coil overs, new drive shaft, set pinion angle, I MEAN NOTHING WORKED!!!! I fought this problem for 2 years, now I am one happy man, and I did it myself so it feels even better.LOL
:punchballs: I guess at this point I just need to do some looking at the axles to verify if they are bent and if so, hope that the 7.5 ones will work ...
Anyone have a good stock set of 8.8 axle shafts they want out of their garage?
They
could be setup wrong, but I highly doubt it. The guy that did them for me the last time is very good. Most of his business is axles and driveline stuff for high performance applications (circle track, drag cars, etc).
I'm going to guess a bent axle shaft or perhaps a bad rotor. That's got to be it. I have 3.73s and my drive shaft does not vibrate at all. I chased a vibration problem for a year or so till I found a bent passenger side axle. If the car was fine previous to the rear swap then it has to be the rear.
Just a FYI but if you have a bent axle I'm going to bet you'll need a new rotor and pads on the side with the bent axle. When I replaced the axle on mine I had to replace the drum and shoes on that side as well. Since the axle was bent it ended up egg shaping the inside of the drum.
There was a bronze bushing inside the back of the tailshaft housing that when replaced helped some with a vibration, but it was an auto.
It might help to check lateral and radial runout to eliminate some components.
Also knowing what order the vibration is a possible way to eliminate some components.
It's been a long time since NVH class but I think there are 1st, 2nd and 3rd order of vibrations when dealing with vibrations in the majority of vehicles in locamotion. You may be able to use a simple small engine tachometer that measures frequency and then calculate what order the vibration is.
Saturday I took off the rear wheels and spun the axles to check to see if they were bent. From what I can tell they are fine. The rotors and brake pads look perfect. I did rotate the tires and it did not change the vibration at all.
I'm going to take her on power tour and just try to stay below 75 mph, that's where it really vibrates. I really don't think its a bent axle...I'm wondering if maybe it has something to do with lowering the car so much. I found this writeup and it really helped me understand the importance of u-joint angles, etc: http://www.hotrodhotline.com/md/html/drive_shaft_harmonics.php
Tomorrow I'm going to get the car on jackstands and check everything one more time with the driveshaft, pinion angle, etc.
I hear ya, the guy that did my 3.73's did them perfect, but 8 years later the 4.33's were aweful, and he has done a lot of gears since then, also he is a good friend of mine, but even when I took him for a ride he said it was the drive shaft.
Just in case anyone finds this thread someday looking for answers to a similar problem--I did have a custom aluminum driveshaft made by Action Machine in South Bend, IN and the vibration is now gone.
That was probably the best $300 you ever spent.lol
I'm sure it was.. I had a 70 mph vibration problem too in my old tbird and it really made me hate driving the car.
Good Fix 50tbrd88!
Thanks guys...the enjoyment level of driving the car has gone up with the new shaft!
Hooray! I loathe vibration issues. I never liked my Merkur after going to a T5. I tried and tried but never got it totally smooth. That gearbox hated that chassis harmonically.
Driveshafts all flex, and the steel one must have had a 'bad' harmonic in your combo. the aluminum one must dampen that out, apparently.
Good thread! Sticky worthy?
You said "shaft"....
I can make fun of it now that that car is fixed.
Darren
I was about ready to give the whole car "the shaft" for awhile...it was that frustrating. I'm glad that's all behind me now.
A vibration you can't find is the worst. I have one in my van that I've been chasing for years. I'm at the point of F it and just drive it till it rattles it self apart.