Please help on vibration problem

[cdover73]

I started a thread a while back on resonating from the rear end. At higher speeds there is a vibration that seems to come from the rear end, but only when backing off the throttle. I originally thought it was improper installation of the 4.10's, but my dealership said it was my drive shaft. He supposedly did a chalk test, which I don't trust, and he DID spin the shaft on a lathe and checked the runout (not on a dynamic balancer). This made sense so I started looking for an aluminum shaft. I CAN'T FIND ONE!! Ford Racing has them but they only go up to '02 Mustangs. Will it fit my '03? The problem is getting worse to the point that I am getting scared to drive the car. If it is the shaft, what is the chance it will fail and cause my car to catapult?
Then I read other threads that describe a vibration due to the gears. How can I truly determine the problem whether the shaft or the gears? I am so frustrated with this because I know it is a simple fix but I can't fix what I don't know is broken and I can't put my finger on it!! :grr:
Note: I have eliminated most of the obvious such as tire balance and condition, loose spare tire in trunk, etc.

Raj, I thought the problem was solved but I guess Murphy is working against me. If you come up with anything on yours, please PM me with what you find.

Thanks,

[Comp Orange 04]

Sounds like it may be driveshaft related. I have seen several posts about vibration after gear install that were cured by going to a aluminum driveshaft. I have also seen many more posts about no vibration after gear install. So I would exhaust all posabilities with your installer, then try the driveshaft.

[Phil]

I started a thread a while back on resonating from the rear end. At higher speeds there is a vibration that seems to come from the rear end, but only when backing off the throttle. I originally thought it was improper installation of the 4.10's, but my dealership said it was my drive shaft. He supposedly did a chalk test, which I don't trust, and he DID spin the shaft on a lathe and checked the runout (not on a dynamic balancer). This made sense so I started looking for an aluminum shaft. I CAN'T FIND ONE!! Ford Racing has them but they only go up to '02 Mustangs. Will it fit my '03? The problem is getting worse to the point that I am getting scared to drive the car. If it is the shaft, what is the chance it will fail and cause my car to catapult?
Then I read other threads that describe a vibration due to the gears. How can I truly determine the problem whether the shaft or the gears? I am so frustrated with this because I know it is a simple fix but I can't fix what I don't know is broken and I can't put my finger on it!! :grr:
Note: I have eliminated most of the obvious such as tire balance and condition, loose spare tire in trunk, etc.

Raj, I thought the problem was solved but I guess Murphy is working against me. If you come up with anything on yours, please PM me with what you find.

Thanks,


Since the dealer determined it was the driveshaft from your other thread, has the shaft been replaced with another factory assembly? Aluminum driveshaft assembly for a 2002 5 speed GT will fit the Mach.

You say this vibration problem appeared after you were at the track? This vibration only happens at high speeds over 100 mph when letting off throttle? So what your telling me is after you had the 4.10's installed you never had it at high speeds until that time you were at the track and since then you have taken it up over 100 mph trying to figure out this vibration!

[cdover73]

Phil,

The dealer has a replacement shaft on order, but no I have not replaced the bad one yet.
I'm not sure if I am understanding your last statement. What are the exclamations for? Is there something you don't agree with? I'll try to clear it up:
I bought the car with the 4.10's already in it(32,000 miles at purchase).
I did run the heck out of it before I took it to the track, but didn't notice the vibe.
I trashed third gear at the track (requiring the TSB) and I guess I started paying closer attention to the car to see what else I tore up. It was then that I noticed the vibe. But I don't know if it was caused at the track or I just didn't notice it before.
I took the car in for the TSB on the tranny, and the mechanic checked the gears and drive shaft. He said the gears were good but the shaft was bad and would order a new one. (Remember, he only checked the run out on a lathe, not a dynamic balancer, and did the old chalk method to check the gear mesh).
Now, while driving along the interstate at about 80-85 mph, I can feel and hear the vibe. It gets worse closer to the 100 mph mark, but I don't make it a habit to go that fast, especially when I KNOW something is wrong. I keep it at traffic flow speed and it seems to be getting worse.

[Phil]

Phil,

The dealer has a replacement shaft on order, but no I have not replaced the bad one yet.
I'm not sure if I am understanding your last statement. What are the exclamations for? Is there something you don't agree with? I'll try to clear it up:
I bought the car with the 4.10's already in it(32,000 miles at purchase).
I did run the heck out of it before I took it to the track, but didn't notice the vibe.
I trashed third gear at the track (requiring the TSB) and I guess I started paying closer attention to the car to see what else I tore up. It was then that I noticed the vibe. But I don't know if it was caused at the track or I just didn't notice it before.
I took the car in for the TSB on the tranny, and the mechanic checked the gears and drive shaft. He said the gears were good but the shaft was bad and would order a new one. (Remember, he only checked the run out on a lathe, not a dynamic balancer, and did the old chalk method to check the gear mesh).
Now, while driving along the interstate at about 80-85 mph, I can feel and hear the vibe. It gets worse closer to the 100 mph mark, but I don't make it a habit to go that fast, especially when I KNOW something is wrong. I keep it at traffic flow speed and it seems to be getting worse.

I was just trying to get a better understanding of the situation with this vibration problem your having. Hopefully a new driveshaft assembly which includes the U-joints will take care of it. However you are saying it's starting to get worse which means a U-joint can be starting to get punished with the driveshaft having out of tolerance run out. A worn clutch/flywheel can cause vibration and so can a wheel bearing as it starts to go bad. The tranny was rebuilt, If a new clutch was installed was the flywheel re-surfaced? Do you feel the clutch pedal vibrating a lot? After the driveshaft assembly is replaced this will tell a lot.

[badappl]

For what it is worth,
I have an aluminum ds...also had extensive suspension work done. Afterwards, I was getting a pretty good vibration @ 115, had my lr (driver's) wheel rebalanced as it looked like I threw a weight. Now the vibration is not as bad but still there @125. Looked @ my rf (Pass.) and cant find an exterior wheel weight on it. Could also be pinion, wheel balance alignment or fact that my harmonic balancer is now off the car. I guess I'm saying that alum. ds wont necessarily fix your high speed vibration problems.
gl

[cdover73]

Thanks guys for the input. I think I will wait for the factory shaft to come in and let the warranty pay for it. If that doesn't help, I will let the pros figure it out. I have always considered myself mechanically inclined, but I give up. If anybody else is having this problem keep an eye for my updates. The least I can do for all the help I get on this site is post the fix, if it is ever found, so maybe the next guy won't have the headache I have had. Again, I appreciate all the advice. :hail1:

[raj]

I started a thread a while back on resonating from the rear end. At higher speeds there is a vibration that seems to come from the rear end, but only when backing off the throttle. I originally thought it was improper installation of the 4.10's, but my dealership said it was my drive shaft. He supposedly did a chalk test, which I don't trust, and he DID spin the shaft on a lathe and checked the runout (not on a dynamic balancer). This made sense so I started looking for an aluminum shaft. I CAN'T FIND ONE!! Ford Racing has them but they only go up to '02 Mustangs. Will it fit my '03? The problem is getting worse to the point that I am getting scared to drive the car. If it is the shaft, what is the chance it will fail and cause my car to catapult?
Then I read other threads that describe a vibration due to the gears. How can I truly determine the problem whether the shaft or the gears? I am so frustrated with this because I know it is a simple fix but I can't fix what I don't know is broken and I can't put my finger on it!! :grr:
Note: I have eliminated most of the obvious such as tire balance and condition, loose spare tire in trunk, etc.

Raj, I thought the problem was solved but I guess Murphy is working against me. If you come up with anything on yours, please PM me with what you find.

Thanks,


Sorry Carey I Just have not been able to get my car to those speeds yet after my driveshaft re-balance. My dealer did say that it was out marginally but still within spec and probably would not cause the type of vibration and humming I was describing. I know some of the guys at my dealer so I do trust their opinion and the have a sneaky suspicion that it is the gears since it is coming from that general area...from what I could tell anyways. I will update as soon as I can.

01 1/2 - 04 Gt's and Mach's use the same driveshaft.