steeda059

I replaced my LCA's with 7,500 miles on them and they were already starting to crack

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

tx_zstang

Sounds like you're getting well taken care of. See what they find, give them a chance.
Let us know what they find. Good luck!

kpd1031

I had the same exact problem after my dealer installed my 410's. My dealer is also very good and took all the same steps yours is taking, even replacing the driveshaft. Nothing worked. In fact after every trip to the dealer, the vibration would move to a different speed, say from 45 mph to 65 mph, it was very frustrating. Finally I decided to take matters into my own hands and I dropped the rear of the shaft, rotated it 180 degrees and made sure I tightened the flange bolts in a star pattern very slowly to the proper torque spec with red locktite. Vibration gone! Bottom line is I don't think the orientation of the shaft is as important as properly tightening the flange bolts. Its a very snug fit between the pinion flange and the shaft and the shaft must be seated properly. Its a real PIA dropping a shaft in your driveway while laying on your back, but trust me it was worth the trouble. After four trips to the dealer with no solution, I was just about ready to get rid of the car. Car is absolutely vibration free now.

1LAP2GO

I agree with SteedaGus. "Your problem is most likely driveshaft balance." I had an 06 GT Vert with a highway vibration. I thought it would go away when I replaced the BFG's at 48k - Nope. I thought it would go away with road force balancing - partially. I thought it would go away when I had a slight bend in one of the wheels straightened - helped a little more. Finally went completely away when I cleaned all of the aftermarket undercoating overspray off of the drive shaft. The company/tech that applied the undercoating, coated one side (the bottom side) of the drive shaft the whole length of the both sections. You wouldn't think so, but the undercoating acted like a balancing weight the whole length, especially as gravity drew it to the very bottom of the shaft as it dried. A little WD 40, a rag and presto - vibration was completely gone.

tdbrown75

Thanks for all the feedback guys! Car is at the body shop now getting some paint work done, after that it's right back to the shop for the vibration issue. With a little luck I'll have her back sometime late next week all purtied up and vibration free. I'll be sure and post an update when I get some new information, but I'm really hoping the third times a charm in this case.

Tim

kpd1031

No vibration before the 410's. Vibration after the 410's. Same drive shaft= same balance. The only thing that may have changed is the orientation of the shaft or the way it was reinstalled. Shaft is good, trust me on this one. Some may argue that since the shaft is spinning faster with the 410's that it will vibrate more. Before my 410's I did 130mph with stock gears and stock shaft with no vibration at all. After 410's vibration at 60mph. The dealer simply did not take the time to properly torque the flange bolts. Do it properly, and you will be happy.

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. If something breaks I can always fix it down the line.

Tim

tdbrown75

I will try this as a last resort, it worked for you maybe it will work for me. The only thing that makes me feel it's something other than a balance issue is the fact that it gets worse after the car warms up completely, if a balance issue wouldn't it be same all the time? Also it's definatley sensitive to throttle input which would also lead away from a balance issue I would think. It's got stock fluid in it right now and I plan on changing to RP after the break-in, not sure if that will make any difference or not.

Tim

ShaneM

you have the pinon angle checked? i was contemplating an aluminum DS and all said that it needed to be precisely at OEM settings (which i forget now) or you get vibration at speed. perhaps the angle is off leading to the vibration. i once had a bad u joint on a 87 lx 5.0 that vibrated at one specific speed and nowhere else.