zkiller

Friction modifier is for the clutch packs in the 8.8. They can chatter without it. Whine is a harmonic vibration.
No gears should whine.
If they whine they are not set 100% correctly. I have 4.10 in my fox body and 3.73 in my S197 and I have never had any whine. My gears were both done by a Senior Ford technician that does driveline work only. He also installed my Kenne Bell supercharger. He is a fox body drag racer for twenty years also. He said the key to doing 8.8 gears is using a new bearing set and accuratley shimming the pinion depth. Many people assume the depth is the same as the pinion they are replacing and dont actually use a pinion depth gauge.
Pay a qualified technician and it wont whine. Let "Billy the grease monkey" do your gears cause he had "dun 'em before" may not have the expected result.

TheDarkPath

If the whine gets worse, get it back to the shop. After the 4th time i had the shop i went to (well known in houston) work on the gears in my car, the whine started getting a lot worse after 200 miles. It got to where I could barely hear my radio at normal volume. The inside pinion bearing was burning up.

Also, a whine on decel won't usually be detrimental to the gearset. Whine on accel can sometimes lead to the gear eating itself. If you pull the cover, you can check the teeth on the ring gear. If they're sharpening, it's eating itself. You'll eventually break a tooth and bye bye rear end.

And sometimes...whine on decel and accel is just annoying and will cause no problems in the future.

As has been said before, if you have gear whine, they weren't installed properly. I still have whine in my 4.10s but it's livable. I just recently checked the pattern when I changed the gear oil and it is off a little so it wasn't a perfect install.

hotstud737

I have a 2007 mustang Gt 5-speed with new 4.56:1 yukon ring and pinon gears installed I little gear noise. Why is there gear noise in the rear end because first off the gears are spinning alot faster then my stock 3.55:1 gears drive shaft is turning faster. Do you know anything about a diablo sport tuner. I have the performance tune on mine for 91 octane, Does that preset tune also take off the speed limiter automaticly ?? Thanks My 4.56 gears allow me to hit redline in 5 gear 6000 rpm at 160 mph

08Bullitt215

Well it looks like my gears are whining. It's a whirring type noise between 40 and 75mph. Goes completely away above 75. Can be heard only upon throttle application. Zero noise when coasting/decelerating/braking. The guy at my work who always services the car says the pinion depth is off.

Now, today I drove an employee's 96 GT with a lot of gear whine, but his was primarily on deceleration and sounded like a doomsday whistle/fire truck siren, VERY pronounced at lower speeds, like 25-30mph or so, very noticeable when turning a corner or changing lanes, but all his shimming/pinion angle was checked and is correct.

I know the guy who did my gears had a hell of a time, but has installed quite a few gearsets in his time. My coworker says the problem may cause the ring and pinion to be damaged (if it was just annoying I could live with it). I am semi-anticipating a hard time from the original installer re: making good on the job, since it was a 5 hour or so job and like I mentioned he was really cursing the car out doing it.

So I guess my question is, what did everyone's gear whine sound like, what speeds etc, and did you have them reset or just lived with it? Thanks.

I hear the same gear whine in my 08 bullitt, took it to the dealer said they didnt know what it was and thought it was normal, which it probly is...

desslok40

I only really have bad whine during decel, seems like most everyone has it during accel,does that scream out an obvious issue with my set-up?

07 GT/CS

I only have gear whine while down shifting. I have a 07 GT/CS with about 16000 miles. It started whining at about 3000 miles. It only does it when downshifting from3rd to2ndand from2nd to 1st.It sounds kinda like a fire truck siren. I asked the dealership about it and they said it was normal for our trans and gears to whine and that it was nothing to worry about. Does anyone else get this affect when down shifting. Also I'm not down shifting at high RPMs just normal driving. Also my car is completely stock from the ground up.

Vapour Trails

I have what I think might be rear diff whine as well. Previous owner had FRPP 4.1s installed by a reputable shop. When I get up to 55-60mph I get a whine/whistle from the back of the car that reminds me of the sound of a wheel bearing starting to go south. There is no noise below highway speeds. I'm not sure if the sound goes away past a certain speed, like others have mentioned. The noise isn't particularly loud or annoying. I guess I will just keep monitoring it. If the original owner had the 4.1s installed by ford, as I understand, it would be covered by the warranty. I suppose he didn't because he was leasing the car.

addison85

woops...wrong thread