driveline vibrations Reply #45 – May 26, 2011, 08:03:28 PM 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, etc2.) trans has been recently changed to T5 from AOD (including crossmember, trans mount, etc)3.) new motor mounts4.) tires rebalanced twice5.) exhaust changed6.) 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-joints8.) cussed, stomped feet, turned red, hit things, etc9.) took driveshaft to driveline specialty shop and had them check balance...balanced out 100% perfectSo 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. Quote Selected
driveline vibrations Reply #46 – May 26, 2011, 08:21:42 PM Did you swap the axles? Maybe one has a super slight bend in it......just enough to cause a vibration. Quote Selected
driveline vibrations Reply #47 – May 26, 2011, 08:24:53 PM 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. Quote Selected
driveline vibrations Reply #48 – May 26, 2011, 08:40:50 PM 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 Quote Selected
driveline vibrations Reply #49 – May 26, 2011, 08:40:52 PM Try swapping just the axles. I believe they're the same. Quote Selected
driveline vibrations Reply #50 – May 26, 2011, 09:05:38 PM 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 Quote Selected
driveline vibrations Reply #51 – May 26, 2011, 09:15:05 PM 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 Quote Selected
driveline vibrations Reply #52 – May 26, 2011, 10:44:49 PM 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.htmI 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 Quote Selected
driveline vibrations Reply #53 – May 26, 2011, 11:09:27 PM Thanks for all the ideas, fellas.QuotePull 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. QuoteTry swapping just the axles. I believe they're the same. 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.QuoteDid 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 itAt 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 ?QuoteOne 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?If you put it in neutral or push in the clutch, the vibration is the same.Thanks again guys... Quote Selected
driveline vibrations Reply #54 – May 26, 2011, 11:40:17 PM 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 Quote Selected
driveline vibrations Reply #55 – May 27, 2011, 05:39:14 AM I'm betting the passenger side axle. Quote Selected
driveline vibrations Reply #56 – May 27, 2011, 11:15:02 AM 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. Quote Selected
driveline vibrations Reply #57 – May 27, 2011, 11:54:50 AM 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. Quote Selected
driveline vibrations Reply #58 – May 27, 2011, 11:58:44 AM 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 Quote Selected
driveline vibrations Reply #59 – May 27, 2011, 01:52:49 PM Quote from: Chuck W;360727You 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 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? Quote Selected
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