vibration thread - aluminum driveshaft cures it!

Topic: vibration thread - aluminum driveshaft cures it! (Read 15638 times) previous topic - next topic

vibration thread - aluminum driveshaft cures it!

Reply #15 – February 25, 2012, 09:57:18 PM

Quote from: 87thunderbirdBlackJack;381913

check the backlash in the rear end... my old 7.5 used to make the car shudder going down the highway. i'd get in it and it would go away, but maintaining speed at 65 70 mph was a vibrating mess.

The guy that did the rearend for me did check the backlash when he had it in his shop. He told me it was fine. My car just vibrates around 65-70 and it does not matter if I'm in the gas or coasting in neutral. But if you slow down a tad it does diminish. It will get worse as I speed up more. Fastest I've been is 110-ish and it did seem to level off and quiet down a tad at those speeds.

Anyone else have any ideas?

vibration thread - aluminum driveshaft cures it!

Reply #16 – February 25, 2012, 11:46:58 PM

Are those MN12 "fan blade" wheels? I gotta see those on your car!!!! Those are my FAVORITE style of MN12 wheel.

vibration thread - aluminum driveshaft cures it!

Reply #17 – February 26, 2012, 01:33:34 AM

Is it a "hum", like a really high-frequency vibration...compare it to a DA sander or tattoo gun? Or at about the speed the wheels are turning, AS IF you had a big chunk of rubber hypothetically glued to the tread of one of your tires?

vibration thread - aluminum driveshaft cures it!

Reply #18 – February 26, 2012, 10:12:34 AM

Quote

Are those MN12 "fan blade" wheels? I gotta see those on your car!!!! Those are my FAVORITE style of MN12 wheel.

No these are 93 Cobra replica's (17x8.5)

Quote

Is it a "hum", like a really high-frequency vibration...compare it to a DA sander or tattoo gun? Or at about the speed the wheels are turning, AS IF you had a big chunk of rubber hypothetically glued to the tread of one of your tires?

Its definately a hum or roar, but you can feel it too. It literally shakes the rearview mirror!

vibration thread - aluminum driveshaft cures it!

Reply #19 – February 26, 2012, 11:24:32 AM

Yeah that's rear end noise. At least that's exactly what my red car does at about 90 or so. I had Richmond 3.73 gears put in. Cost about the same, I should have bought Ford Racing ones or tracked down a set of unabused ones from a factory 3.73 equipped ranger or something. They're not bad, like I said about 90-100 they do that kinda bad, you get up above a buck it goes away LOL.

Either a factory fault or that rear end was modified or re-setup.

vibration thread - aluminum driveshaft cures it!

Reply #20 – February 26, 2012, 08:08:01 PM

I still keep thinking driveshaft. I know it was professionally balanced, but it makes me wonder if the change from 2.73's to 3.73's has the darn thing spinning twice as fast and is causing some wierd harmonic inbalance or something.

vibration thread - aluminum driveshaft cures it!

Reply #21 – February 27, 2012, 07:52:27 PM

So tonight I had to move the car out of the garage. When I went to move it back in, I noticed a chattering sound coming from the rear of the car. I have also noticed in the past a "clunking" noise coming from the rear when I hit bumps. It also used to clunk pretty loud when I had the AOD and would put it into reverse.

Do you guys think the combo of stiff springs and aftermarket control arms could be causing these noises and the vibration I am experiencing? I am thinking about putting the stock control arms back in along with the TC spec Moog springs I have just to see if it eliminates anything.

vibration thread - aluminum driveshaft cures it!

Reply #22 – February 27, 2012, 08:50:35 PM

Did you change anything right before the vibration started? Does the vibration change any whatsoever with tire rotation? How about the exhaust hangers? Could exhaust vibrations be traveling up the hangers and into the cabin? I am really grasping for straws here. This would be a great time for Tom to join in.

vibration thread - aluminum driveshaft cures it!

Reply #23 – February 27, 2012, 09:44:22 PM

Now that the tires and wheels are eliminated as a variable, I wouldn't suggest chasing your tail replacing suspension components. Retorque all the attachment points to eliminate a loose component. Unless the bolts you put into the upper control arms were too small (which I've done...), if everything is properly torqued, there should be no clunking from the suspension.

From your discription of the vibration, it points to driveline.

Though it may have been checked in the past, the first and simplest item to check is the driveshaft. Clunking can be u-joints or differential. This has been going on for some time, it is possible the vibration has caused issue with the differential or worn out the u-joints.

I believe I mentioned this is past threads: I had a vibration issues due to the angle of the engine and the transmission in relation to the driveshaft. I had drop motor mounts (on a Mustang), this caused the tail shaft of the trans to rise, messing with the angle of the driveshaft as it entered the trans: I replaced the motor mounts with standard units and the issue was solved. The same issue surfaced on the Thunderbird when I intalled the T56 with an aftermarket crossmember. The crossmember pushed the tailshaft very close to the trans tunnel: I drilled lower holes in the mounting brackets, problem solved.

As has been stated, it has to be something simple. Just not easy finding it...

vibration thread - aluminum driveshaft cures it!

Reply #24 – February 27, 2012, 10:28:41 PM

hmm.. didn't think of this before, but since the bolts have been mentioned..

make sure none of the mounting holes have been egg shaped if you find any loose/not tight enough bolts.. it's a common problem with 70's broncos/F150s for the panhard bar bolt to bash around when the bushing gets a little worn and beat the hole (in the bracket on the frame) egg shaped, causing front end issues and the occasional noise

vibration thread - aluminum driveshaft cures it!

Reply #25 – February 27, 2012, 10:38:32 PM

Just do a random check. Jack up the rear end of the car and put it on stands leave it in gear and roll the tires back and fourth and listen. You can uncover a bunch of issues. If you hear a loud clunk it could be the pinion bearing or a U-joint.

Im still leaning on one of the carrier bearings being bad.. or possibly an axel bearing.

vibration thread - aluminum driveshaft cures it!

Reply #26 – February 28, 2012, 12:12:36 AM

is it possible... that one time or another in the cars past... that it ran over a big ass hole... and possibly very ever so slightly bent a wheel hub... and now it causes vibration from the teeny tiny warble that its causing amplified 10,000x when at high speed?

vibration thread - aluminum driveshaft cures it!

Reply #27 – February 28, 2012, 06:00:22 AM

Pinion bearings and carrier bearings that go south cause exactly what you are describing. They MOAN at speed. Also check the spider gears and cross pin and pin retainer. I have seen them chewed up pretty good on many 8.8 rears. Clunking is not good from a final drive. I had a customer lock up a diff by having the cross pin let go. Is your diff posi??Without driving the car it is difficult to diagnose. But if the rear gears are not set up correctly. And i have found most so called experts dont know how to do it or lack the proper tools as well. Normally tires will not cause this condition as you said they were new and swapped from front to rear. Also try indexing you drive shaft 180* in the yoke or . This just may point you in the right direction. Now was all the rear axle bearings changed when the gears were replaced??? And is all the PRE-LOADS CORRECT!!! Also did you leave the rear vibration weight on the 8.8 from the turbo coupe rear??? Very important to also have the weights on the tail of the 5 Speeder conversion. Is the tail weights installed on the tranny?? This is stuff that has to be checked. The drive shaft was checked as you explained but is the U joints ok?? Clearly you have a drive line vibration that plagued ford and they came up with weights on the final drive and tranny tail. Good luck

Below is a pinion race i changed to correct a bad vibration my truck had. Notice how the thing is chewed up!!!

Pinion angle most likely wont be an issue as i am sure you compared the new control arms for length with the originals. And lowering the car is not a factor most of the time because the 4 link keeps the arms in the proper drive shaft angle. You would have to be way out. Example when guys raised those 4X4 vehicles through the moon they really did not vibrate. So check you diff and by the way the race i posted was from my truck and if i did not cut the cage off and remove the roller bearings the thing looked PERFECT. Also back lash is important and should not exceed .008 in a 8.8. I normally run the street driven 8.8 at .005. Always replace all the races and bearings when replacing final drive gears. I only use FORD gears in our shop. I personally dont like the aftermarket off brand stuff. just me could be wrong. Good luck

vibration thread - aluminum driveshaft cures it!

Reply #28 – February 28, 2012, 07:50:24 AM

Now that you mention the clunk in reverse...

While it's jacked up be sure and and push/pull on each rear wheel in and out, there should be just a hair of slop. I forget the actual figure. But my silver cat has plenty of shaft end-play, which can happen from worn out Trac-Lok clutches. Though it burns both of them pretty well, so I don't know. I haven't ever done a rear end, I'm going to this summer half just to be able to say I know how. But how is thrust-bearing accomplished side to side? Just the sides of the framing that holds the main carrier bearings? I remember when my red cat's 3.73s were put in, going around a broad bend in the road would make it hum more, obviously shoving the gears into each other a little more. Then of course after about two weeks the break-in was done and again, at any speed up until about 90 there was absolutely no noise back there at all.

vibration thread - aluminum driveshaft cures it!

Reply #29 – February 28, 2012, 08:01:09 AM

Again, I am just grasping for straws. If your rear is limited slip, it needs the right amount of anti-slip additive. Without it there may be some strange noises and vibrations, but they would change as u make turns.