richmod

will gear whine (decel) or (pinion) bearing noise still be there in neutral?

AmericanMuscle4.6GT

well, when i first start the car, and i let the clutch out in neutral, it begins a rattling sound, like something is engaging.


could you be referring to the same noise, that when you rev it in neutral, it makes like a winding down sound? like a full 5500 RPM rev? and u can hear it better with the hood open?

richmod

well, i definitely have some whine on decel (more of a flutter) that goes away on tip-in. Also goes away if I shift to neutral. I also have a hum/moan type sound above 25 mph, which is independent of throttle position or gear/neutral. I'm fairly confident the decel whine is the gears, i was mainly wondering if the hum could also be differential related.

btw- i have an auto tranny (sorry - shoulda mentioned that earlier).

Centurion96

From my experience with Ford 8.8 rear ends eating pinion bearings in their trucks (as in my Bronco and F-150), a failing or stressed pinion bearing will whine under acceleration and deceleration but when you put the auto in neutral the whine goes away. As I see it the force of the motor is pushing against the resistance of the wheels and axles under acceleration. When decelerating the force of the wheels and axles is working against the dynamic braking of the motor. Both of these cases would produce a whine with a failing pinion bearing. Now by putting the auto tranny into neutral you remove any opposition to the forces exerted by the rotating wheels and axles.

If this is something that has been coming on slowly over time without you modifying your suspension, then one of your pinion bearings is going south. If however this is the result of a suspension change then you need to have your pinion angle checked.

richmod

So from what your saying, the hum/moan I'm getting (which is present under all throttle conditions and in nuetral) is probably not gear or diff related, correct?

Centurion96

No, not necessarily, I'm not sure what you mean by moan or hum. A whine is like when you put your car in reverse and accelerate. Your differential gears are cut to make the least amount of noise and provide the best contact when driving forward. When in reverse, they whine. When a pinion gear starts to fail the sound is much lower in pitch. The sound increases over time and you don't realize by how much until the vehicle is fixed and you hear how quiet it has gotten. The loudness of this sound changes with acceleration or deceleration but in my cases it has almost completely gone away when the tranny was put into neutral. Notice I say almost, I don't hear anything but others say they can hear it. I do have a slight hearing loss due to working on flight lines for several years. Jet engines have caused me to have problems with 3000 Hertz and each of it's harmonics up to the upper limit of my hearing range. I had a close friend who is a very good shade tree mechanic tell me about my rear end noise 6 months before I heard it. He had a very good trained ear. It was also funny watching two mechanics trying to hear where the sound was originating while at the dealership. One was driving and the other was lying down on the floor boards with the rear door open and his head hanging out. They drove back and forth behind the dealership for about 20 minutes before deciding it was the diff. Here's the difference between warrantee and non warrantee work. On the warrantee work they pulled the pinion gear and replaced the bearings. On non warrantee work they refused to pull the pinion gear and stated it was standard policy to replace the whole axle rather than mess with the pinion gear and it's bearings. I decided not to have them work on it and took it to a 4x4 shop in the area. They pulled a fast one on me by using all used parts in the repair when I specified and paid for new parts. Needless to say the sound came back within 6 months. I opened up and inspected the rear end to find that the one shot sacrificial pinion nut, crush sleeve and pinion shaft retaining bolt had been reused. They took a cold chisel and crushed one side of the nut and bolt to keep them from backing out. Gotta love Ford and local mechanics, I do all my own axle work now.

Since you haven't provided any additional information, I assume that the supension has not been modified. If your vehicle is still under the bumper to bumper warrantee, then I suggest having it checked by the dealer. My wife's 98 Grand Marquis started to develop rear end noise when it had only 20K miles on it. I opted to have the dealer work on it as it was still under warrantee. Upon return they told me that the ring and pinion gear were bad but to me it didn't sound like gear noise. I then checked the ticket and noticed that they replaced the front and rear pinion bearings as well as the ring and pinion gears. I suspect the bearings were the real culprit. The Merc now has 149K miles on it and it has not had another problem with the rear end.

I really need to crawl under my new Mustang to see how the carrier housing differs from my 96 C-150 and my 98 Grand Marquis.

richmod

Okay, here's my situation: Initial problem was axle hum above 65 mph only on acceleration. Dealer did TSB 5-20-02 (ring & pinion) - obviously didn't bother to set them up, 'cause they whined like a police car from 60-30 mph decel. Same dealer tried 2 more times to fix it, improved it but whine not gone. At some point in this process the hum started again, but this time at 25 mph and up until about 70 - independant of throttle or gear. Took it to different dealer, did TSB again and replaced ALL bearings (wheel bearings included), got rid of most (not all) of the whine, but hum was still thereAND he created a vibration at 70 mph. tried to fix that, couldn't - so they put in a whole new rear end. Guess what - new rear end had slightly worse decel whine, hum is still there, and vibration still there. After trying to rephase driveshaft about 3 times, they finally replaced the driveshaft by swapping it with another GT on the lot (new driveshaft from factory actually made vibration worse). So now - no vibration, but some mild decel whine 55-40 mph, and rear end hum above 25 mph (at 28-30 mph it is loud and has a woob woob type rotational sound to it). I'm going in next week to swap my 18" BFG wheels for 17" to see if anythinng changes thus isolationg the tires as the problem(s). I doubt it. BTW - all stock, no mods (yet).

Centurion96

Man, I feel your pain. This is probably a dumb question but did the dealerships check pinion gear to propeller shaft angles? I would guess after all that work that they would. Interesting that with each repair the problems changed and then with further repairs original problems re-occured. I read somewhere on one of the Ford Mustang forums that the replacement gears Ford uses are not the same as the originally installed gears. I don't know if it is true or not as I haven't been able to confirm this rumor.


Your problems have gone beyond my experiences and I wish you luck.

richmod

Is that also known as the pinion angle? If so, I was told that it can only be changed with adjustment control arms.