tdbrown75

I have been fighting a vibration which I first noticed in December, about a month after I had my 4.10s redone by a dealer due to a bad install at a speed shop. The vibration occurs at highway speeds (55+) and increases in frequency as the car speeds up. By 75+ it's noticeable even on terrible roads. It's in the floorboard and there is an audible rumble associated with it. It seems to worsen once the car gets warm and is worst when cruising although present on both acceleration and deceleration.

These are FRPP 4.10s dealer installed, full bearings, cups, etc. At first they were silent, but over the past few months they developed a slight whine and howl, so last week I returned and the dealer installed set #3. Again full bearings and cups were installed and they were not able to get them 100% silent. After a call to the Ford tech line they ended up installing a new axle housing due to the original being warped? In any case I now have the quietest set of gears I have ever "not heard".

Problem is the driveline vibration persists. I know its not a tire (I swapped wheels form another known good car), I have new gears, new axle housing and what I think is a perfect install all within spec. On previous visits drive shaft balancing was attempted with the "worm clamp" procedure and the driveline angles were checked and then corrected with Adj. UCA and Panhard bar (I have Steeda Ultra-lite springs and FRPP dampers).

The dealer is mod friendly but I'm starting to worry about them giving up and claiming it's due to the suspension modifications. I had the UCA professionally installed and the pinion set at -2 degrees and it made absolutely no difference. Nothing's made any difference so far, the darn vibration just persists through everything we try. What the heck else could be the cause here?

Tim

Gtpony325

Do u have a one piece driveshaft or the stock driveshaft? I know when i had my 3.73 gears installed it had a crazy bad howl on the deceleration. That was due to one bearing having a scratch on it. I replaced all the bearings and no more noise. But since you have already replace tye vearings a few times the drive shaft is the only thing i can think of

tdbrown75

I'm running the stock shaft. I wonder if someone didn't drop or damage it along the way, it's my #1 culprit right now too.

Tim

Gtpony325

The driveshaft could be damaged or it might just need to be balanced. i think before you dive into it too much you should try to figure out some way to test it. About the only way that i can think of is to get ahold of another driveshaft and out it in ur car. Not exactly a super easy project

tdbrown75

Yes and if so that could have been what caused the last set of gears to develop noise. It's still at the dealer (body shop, a whole 'nother story for another thread), so I'm not driving it right now. Once done with the body shop it'll go back over to service for the vibe.


Fortunately it’s still under the extended power train warranty and everything that's been done so far has either been covered by Ford or the Dealer. I'm headed down there tomorrow morning to return a rental; I think I'll be having a chat with the service manager about the driveshaft.


Tim

Gtpony325

Ya i know all about the body shop. But i hope everything goes well when u talk to the service manager. I have never had any luck talking with anybody from ford when it comes to anything performance wise with my car

ieatv8

Have them rotate DS 180 degrees.
Simple & worth a try. My .02cents

tdbrown75

A good suggestion and I’ve seen more than one thread where this was the cause. In my case they tried indexing the DS on the previous visit (when they determined driveline angles were off) and it had no effect on the vibe.

Tim

Gtpony325

What happend to the car that made the drivelines angles skew from where they shoyld be??

tdbrown75

It was lowered with Steeda ultra-lites, but this was nearly 4 years ago and I drove it three and a half without any vibrations whatsoever. I guess the angles were just slightly "out of spec" so they fingered that as the cause and sent me packing.

I had to get the control arms to correct the angles before they would continue to troubleshoot further. In hindsight I should have just threw some stock springs back in there and brought it back, but at least I know it's all in spec now.

Tim

Gtpony325

I see. I know all about having to return my car to stock in order for ford to touch it. I had to strip every mod off my car last year before ford would even look at to tell me why i had a random misfire on the left bank. And by every mod i mean the car had to undergo almost 4 full day of work to bring it back to %100 stock. I hope u dont end up having to do the same thing

tdbrown75

I’m thinking I’ll probably be OK, we are just talking a few suspension mods and considering the noise was there before I installed half of them I don’t imagine them going there. The dealership has been awesome, they stand behind their work and have not given me any trouble over mods to date. They are a FRPP and Roush dealer so mods don’t scare them like others. However Ford maybe another story if they end up having to go back to the tech line. Just going to keep after it, eventually it’ll make itself known (I hope)!

tdbrown75

Spoke to the shop foreman this morning and discussed the situation with the car. He’s going to have it back on the EVA (electronic vibration analyzer) to reassess the vibration now that the rear axle has been changed out and the gear noise is gone. We discussed everything that’s been done to this point, talked about the mods, pinion angle and possibility of an unbalanced drive shaft.

His next steps will be to re-index the driveshaft, if that’s ineffective he will weight it with clamps to see if he can identify an imbalance. He felt confident he could narrow it down and even suggested we was going to try a few different pinion angles himself to completely rule that out as well. I even mentioned returning the car to stock ride height and he said it would not be necessary.

I didn’t feel I needed to sit there and make any demands about changing driveshaft’s or anything else, I like the approach he is taking and through the process of elimination this will eventually get narrowed down and eliminated. I consider myself very fortunate to have access to a dealer like this; I can’t even imagine the cost of trying to figure this out on your own.

Tim

70MACH1OWNER

Gee Tim,
Sorry to see your having all these issues. I know the shipping would be expensive but I have a perfectly good stock DS in the garage I will never use. It's your's if you need one and cover the shipping.
Scott

Gtpony325

I also have a driveshaft you could have if younneed it. I dont kno what the shipping would be from chicago would be to where you are but its your if needed.

tdbrown75

You guys are awesome thank you so much for the offers! I’ll let you know how the dealer thing comes out and depending on what happens I might take one of you up on the offer. Thanks a lot guys, I really do appreciate it.

Tim

Gtpony325

No problem man.

tdbrown75

Well the car should be back over to the shop on Saturday (it's in paint now) and we will continue troubleshooting. I'll post some updates next week when they start working on it again. Got my fingers crossed!

Tim

tdbrown75

After another week in the shop the dealer has reached the end of the line. And after 20 minutes on the phone with the Service Advisor I’m pretty sure I’m just going to give up too. In a nutshell after another attempt with inconclusive EVA readings the dealer ended up having to contact the Ford Hotline, who basically told them the 4.10 gears are the cause of the harmonic vibration. They provided some supporting technical detail, most notably NVH data Ford has specific to the gear set that almost exactly matches the EVA readings they took on my car. They have a file with the readings and information for me to review when I go pick it up, but I also plan to talk to the Foreman tomorrow to understand exactly what they did with it (tests, procedures) and to ask him why he thinks the EVA rules out DS balance, etc.

I know I know, I’ve seen the “I have 4.10s and no vibrations at all” threads too. But here’s where it gets really interesting. I got a ride from my buddy last Friday over to the dealer. He’s got a 06 GT with 4.10s and guess what? HIS DOES IT TOO! The exact same humming, harmonic vibration only his was masked by his FRPP stingers, some gear whine and suspension rattles. He does not feel he has a harmonic vibration, I suppose it’s all relative to the other noises the car makes and ones “sensitivity” to such things. I know a few other Mustang club members with 4.10s and you can bet I’m going to be taking some rides this summer to test the theory.

I suppose I could try a replacement DS next, or perhaps 3.73s (which would force me to mess with my tune for months on end again), perhaps change the pinion angle, or ride height, or a dozen other variables which could be the cause if it’s not in fact the gears after all as the Ford Engineering hotline claims (what the heck would Ford know about it anyway). In fact there’s probably no end to the things to try, replacement parts, money and time to invest trying to figure something out that I only ever occasionally experience and doesn’t seem to have any negative impact on performance anyway. I think the fix in this case is to quit hyper analyzing every little noise the car makes, crank the radio up and enjoy the hell out of the thing.

Tim

Gtpony325

Sucks to hear that the dealer cant figure out your problem. I wouldnt go changing to a 3.73 just to get rid of the vibration. My friend has an 07 gt with 4.10s and doesnt have any vibration at all. But with my 3.73 i had a really bad whine during the deceleration that turned out to be a scratch on the pinion bearing. That could be something you could look into. Other than that you seem to have some ideas on what you can try