Gear Install - Now Whines
 

I just had 3.90 motive rear gears put in my 2010 mustang. now it whines significantly, and is louder the faster you go. It whines under acceleration, deceleration. Its loudest when you are just coasting and in neutral or put your foot on the clutch, so there is no load. What could cause this whine?

The shop didnt follow the directions that came with the kit bc hes done it for years. He is saying it looks like the ring gear was lapped but the pinion gear wasnt, which doesnt make sense because they are lapped together as a set. I'm having him take it out to check the serial numbers. if they match, then its a good set. But the shop keeps saying its the gears.

He set the backlash at .005" when motive recommends .008"-.012" and stock it was .012". Could this cause it?

Right now I'm having the shop take it out and check the serial numbers on the gears to make sure they match. after that, I'm having him install it per the instructions that motive provides (with a new bearing) to see what happens. I just really want to know what could cause the gears to whine. Could it be the backlash?

I googled it and saw a few threads in different forums where guys had similar problems and they had their backlash around .006-.007 and going from that to .010-.011 helped a ton. I called the shop and asked him to adjust the backlash to around .011-.012 and see how it sounds. ford recommends .012-.015 and motive recommends .008-.012.

Sorry to hear about the gear whine.

Not everygear installation is the same on every car and companies recommend certain backlash and specs because it's what their products work best with.

I recently had my gears switched to 4.10s from 3.55s. They are absolutely silent and make zero noise.

A backlash adjustment will hopefully change your noise.

The guy who did my last gear install said 8.8's need minimum backlash. He sets them a .008".

Unfortunately 3.90's have a rep for making noise. It has to do with the number of pinon and ring gear teeth and how they mesh.

Noisy gears suck. Sorry to hear about your misfortune.

yeah well i wish i had known that before. the gears are still loud being set to .012" (factory setting). its annoying and i wont let it stay like this. I'll most likely be getting some 3.73 FRPP gears and having a different shop install them. and spend another $600 :(

Sorry to hear that Ice. I just finished installing my 4.10's this week. I used FRPP gears. All of the Ford Service manuals call for .008-.015 backlash, with .012-.015 preferred. I'm right at .012, and all seems well, no noise yet. Another thing to check would be the pinion height, this is very critical. Unless you have the right tools to set this, it is very difficult to get it right. Before changing the gears again, check the wear pattern, that may be able to tell you what's going on.

You're the victim of a bad install. If he had set the backlash correctly the first time, you would have no whine. Unfortunately, after you drove with them in for a while at the improper backlash setting, they established a wear pattern that caused the noise to continue even when adjusted to the proper backlash (if the mechanic even reinstalled them, which I am suspicious of). There is no "noisy" gear ratio. All gears should operate silently and any mechanic who tells you otherwise does not deserve your business.

^ diabolical i have heard that so many times. and it sucks bc now i have to spend anohter $170 on gears (im gonna get 3.73 frpp) and i dunno who to take it to. this guy has been doing trannys and gears for many many years, but he messed up on this. there is another local guy who will do it for $400 but i dont have another $600 to spend on gears right now.

The drive line shop I used would not guarantee FRPP gear sets to not whine. If I wanted a guarantee of no whine, I would have to allow them to choose the parts. Wound up with a FORD OEM 3.73 gear set which is absolutely quite. They tried a US Gear set first but it whined. So they redid the job under their warrantee. I paid more for the job than some report although much less than the Ford Dealer wanted.

It is in the install, and any shop that tells you different is just covering their own butt.

Your BEST bet starting out is to locate a shop who will work under the following circumstances:
1) Set a price, complete, and have them buy the parts so they can warranty them
2) For agreed price, they will guarantee there will be no rear end noise when finished.
3) If there is any noise at all, you will return and have them re-do it for no charge to you, including fluids, parts, or labor.
4) They will make it right, regardless of how many tries it takes, at no additional cost to you.

When I set out to find a shop willing to follow those rules, I encountered a lot of places unwilling to guarantee their work. Eventually, I found a shop who was willing to do it. The price was at the top of the spectrum, but if I had done this to begin with, I would have saved thousands. The first install by that shop was perfection, and after 600 miles on the new gears, still quieter than stock. (3.73 frpp gears btw).

Previously, I went through 2 sets of gears and 4 reinstalls. One swap was to go from 4.10 to 3.73. I paid for full labor 2 times (initial 4.10 swap and initial 3.73 swap), after which the shop paid labor for reinstall but charged for parts and fluids (gets expensive with royal purple each time). Regardless of the fact that the mechanic who did all those installs and reinstalls had done over 1000 rear ends in his life, in the end it was his failure that caused the noise. The first install showed a perfect pattern, which we rechecked after 500 miles, and I witnessed the pattern myself. Everything was in spec according to the instructions. Despite this, there was noise.

The last mechanic to work on it (the one who did it right), was able to point out many flaws, including the necessity to shim the pinion bearing, something the first mechanic never did.

I would let the shop you had do the gears have one more shot at it, and then look elsewhere for a better mechanic, one who will guarantee his work. If the shop is associated with one of the big parts stores, they may have an insurance program that will allow you to take it elsewhere and have all labor covered (as well as any parts that store sold to the mechanic, hence the reason to have the mechanic buy the parts).

Good luck, there is NOTHING more irritating than whining gears, I put up with it for over a year, and never should have had to.

where in va are u at??? i'm in northeast tn..and there is a very good guy here

my motive 3.90 are quiet as can be,been to the track and never did a break in period, just floored it right away to see how they were, still no problems or noise.

im in northern va

Rear end gears don't need a break in period. After you get them up to highway speeds just once after leaving the install shop, the pattern is set.

I want to believe that so bad. I'm going in for a gear and differential swap and really want 4.30's, unfortunately almost all the feedback on them is to expect noise. I'll ask my gear guy about his experience with them. I've been the victim of a bad install before and this guy knew what the other shop did wrong and was able to install dead silent gears for me.

To the op: spend the money on a good install and be done with it. It's not worth your time or piece of mind to put up with noisy gears.

I'm glad you are looking at the 4.30s.

I did the same thing as Bruce and was very happy about it. If you have the time or connections, talk to people who race at your local drag strip and ask them who they have used. It's what I did and it worked out really well for me.

Believe it or not, the whine I initially had with my 3.73's is now nearly gone. At first there was nothing, then shortly thereafter I noticed it.....now? You have to really concentrate to hear it.

I promise you, that's the way it is. I worked in two automotive performance shops before hurricane Katrina. The reason I quit the first one was because the owner (who also did the gear installs) had a bad habit of giving customers the runaround every time he did a crappy install (not just on gears, but on anything). If a mechanic won't warranty his labor for a gear install against gear whine, find a new mechanic.

I'm in NE TN as well and looking someone to install gears. Who do you recommend?

I remember the trouble you went through with the dealership. Is this your second set of 3.73's or did they just reinstall the first set?

Hey Man,
I wish i could tell you something better but from what i have heard you may just wanna get a new gear. If you do, get one from ford racing.
I just had a mustang shop put a 410 in mine and had the same issue. at 1st they tried to tell me that there was nothing wrong. So I spoke with a buddy whos been racing for about 20 yrs and he told me it cause they didn't use the tool to make sure the shims, spacing, and depth were set correctly. I took it back again and told them what he told me and advised them that they could redo it our I could have someone else do it and send them the bill. After they pulled it apart and used the tool it was perfect. Although, from what I have heard from guys who tried to use after market ring n pinions all had bad luck with them if they were not set up right the first time because it causes a wear pattern because the metal is not as hard as the ones from ford racing.

noe's performance in morristown...scott is extremely good and he knows what he's doing.