Rear End Vibration!?

[4.6andSlicks]

I also had FRPP 4.10's (w/bearings) professional installed in a mustang with original 3.73's by a trusted speed shop in the area. I had the same vibration as described. It almost sounds like a bad bearing.

I took it back to the shop and the tech also thought it sounded like a bearing. Suspected and changed the pinion bearing and checked the gear install. I picked it up and it still had the noise. It's had it for almost a year now and it's no worse.

Tell me if yours is the same. Under power I hear it fairly loud at around 80. If I push in the clutch and take my foot off the gas, it's quite as a mouse. Everything is still spinning at the same speed. If it was an imbalance, I don't think the sound would go away.

 

[Nightstick]

Had a shop put 3.73s in my Gt. Had very noticeable vibration above 65, esp. when lifting of the throttle. Was told it may be a bad u-joint after the tech. road in the car. Decided I would take a look see....turns out they had the D/S rotated
180* on the pinion flange from where it was. I lined up the very faded factory paint marks(shop chose not to mark it) and no more vibration.

 

[hotcobra03]

for those who are wondering?READ THIS

[/url]http://www2.dana.com/expertforms/depdf.aspx?prod=JOI............DRIVESHAFT INSTALLATION MANUAL

 

[YLWRCR]

Interesting discussion folks.

I too had brand new FMS 4.30 gears installed in my 96 Cobra two weeks ago and am noticing just a bit of vibration starting at about 2800RPM in 5th gear. I can hear/feel the high frequency vibration throughout the entire car but interestingly the shifter is not really rattling at all... It continues at about the same magnitude as I speed up too. I have not yet had a chance to get it above 100mph to see if it goes away after a certain speed. I do notice that it gets just a bit worse once I let off the throttle or put it in neutral letting it coast. If I am at full or part throttle it is less detectable. It continues like this until I slow down to below 60mph or so when things go back to being extremely smooth. However, it doesn't seem to be present 100% of the time (even at or above 2800rpm) which throws me for a loop... It seems to be 100% speed related and independent of the car being in gear or not.

This was not present at all with the 3.27 gears.

Here are my thoughts:

1.) Since I did not perform the install myself, perhaps the driveshaft orientation was not marked and the driveshaft was installed 180* rotated from its original orientation relative to the pinion flange? Does the factory leave any marking that will allow me to easily verify this?

2.) I mentioned that I start feeling the vibration at ~2800 RPM. Since I am using a 305-35-18 tire, that means that with my 3.27s, 2800RPM came out to approximately 100mph, a speed that I almost never drive. Maybe once or twice for a few seconds but I was surely not paying close attention to vibration. Now I have 4.30 gears, which means that at that same engine RPM in 5th gear, and same driveshaft rpm, I am now only going 76mph! This leads me to believe that perhaps that vibration may have been present before, however, I was never rotating that shaft fast enough to notice?

The individual who swapped my gears is very experienced and has a great deal of knowledge on gear swaps (probably done over 200+).

I am also using Royal Purple 75W-140 which already has the limited slip additive (no Friction Modifier required). Not sure if it matters but I also had the trac-lock rebuilt at the same time.

I will probably start by checking the driveshaft orientation. If that does not help, I may try the aluminum shaft... Can't believe how much the prices have increased for these things since I purchased on 7 years ago for $150 lol

One other key note, I removed the 6lb dog-bone under the rear differential about 6 months ago with no notable adverse effects. Would it make sense to add it back to see if it helps?

I look forward to any feedback you can provide!
Thanks guys
YLWRCR

 

[wmburns]

wow! Heavy tech!

When I read some of the detailed information in the Dana site, it's a wonder that more installs don't have problems.

http://www2.dana.com/pdf/J3311-1-DSSP.pdf

To the poster that removed the weight on the pinion, the weight is there to keep the pinion angle in check (the diff case is back end heavy).

So what about lowered cars? Doesn't that change the pinion angles?

 

[merc123]

3.73's installed by Ford. I put close to 30,000 miles on them before something gave way in the tranny (bearing?) and had 0 whine and 0 vibration.

 

[fast97gt]

I will, alrite people I swapped u joints in my 97, it had no vibes at all, even 30*** miles after the gear swap. However when I did new u joints I got a vibration, I had put the ds on the pinion flange in the wrong location, turn it to the next set of holes and fixed it. Now I'm agreeing with the ds not spinning faster theory, it spins quicker through the rpm range but your ds is spinning the same speed once you hit top gear, now hold on ok, here's my theory, my 5th gear is like my 4th gear, so with me in 5th with my 4.10s is like doing 70mph in 4th with stock gears. So yes you can say its spinning faster but its not the same. So if had no vibes at 70 in 4th with stock gears you should have none now. When they had the ds off they could of not put it back in the right holes
Posted via Mobile Device

 

[Kilgore Trout]

i get the drive shaft imbalance possibility, i dont think its that, just for the simple reason that

before 75mph = 2000rpm - no vibration
now 2000rpm = roughly 55mph with vibration

sooooo if the driveshaft was imbalenced before, it would have vibrated then at 75 or higher. I am wondering if the shop might have accidentally installed one of the bearing races in a little cockeyed, or if the lash is set too close. i watched him check the backlash and it was .10 which is good, but if the gears are heating up and expanding, maybe that lash is closing up and causing the roar. What do you guys think?

If they did not mark the drive shaft prior to removal then its a crapshoot as to whether they will bolt it back on the SAME WAY IT WAS. These kind of sloppy mistakes indicate a poor shop.

ALWAYS MARK THE DRIVE SHAFT PRIOR TO REMOVAL so it goes back on the same way it was.

 

[Trav4011]

Sorry to rehash an old thread, but, I think I have the same problem..

I just had 4.10's installed in my 2011 GT, and I have a vibration issue from about 45 and up.. It's especially noticeable when I decelerate through 60-45mph. I'm going to jack up the car and check the drive shaft. Hopefully, it's just rotated from where it's supposed to be.

Travis

 

[d98gt]

I hope its an easy fix such as that for you. Report back and let us know.

 

[hotcobra03]

viberation

wow old thread here...

funny i just got tired of mine 2 months ago..changed the pinion flange...100 percent viberation gone..

ive had this battle with another site,,,

the driveshaft is balanced on a machine with slip yoke and flange yoke as a unit...

the pinion yoke only centers the driveshaft in the rear,

the output shaft on trans centers the front,

the pinion yoke is balanced on its own...

my pinion flange..see hole in side...thats how they balance it,they remove metal

here is a shaft being made in a balancer,,notice its bolted here with ubolts,,,ours would have a flange setup

here is fixture our style bolts to in balancer...notice other holes...thats for other size flanges...the lip in middle centers shaft just as pinion flange
View attachment 206765

here is what the shaft in pic would be bolted in..notice tabs on ends that hold ujoint from sliding side to side,,that centers the driveshaft.

 

[twogts4us]

REAR END VIBRATION?

Sorry, couldn't help myself...

 

[Kilgore Trout]

So much great info and then zerogts4us has to be a child. Nice.

 

[twogts4us]

So much great info and then zerogts4us has to be a child. Nice.

There ain't nothin childish about that a$$. Get over yourself and ignore it if you can't handle it.

This is especially surprising coming from you, the one who loves to add his two cents whether the thread starter asked for it or not.