JimsGT

I'll try to make this as short as possible: I had went from 3.31's (on my auto. 06 GT) to FRPP 3.73's. the 1st installer only used the gearset and new fluids (RP & Ford friction mod), I had a slight noise, (like a howling), between 60 and 40 mph on coast, and slightly on accel. It got to the point that I questioned the 1st installer about it. He said don't worry. I needed a second opinion. Well, now 8k miles later, I went to a SVT/ Motorsport Ford dealer, who has a great rep, to look at the gears. They found bad axle seals, driver's side axle bad, and the pinion depth was not set right, needed a new r & p. They installed the new r&p, new axle, seals, all new bearings, cups, they used the Ford housing spreader tool,install kit, the whole nine yards,( I basically have a rebuilt rear axle) and guess what? SAME noise, even after 500 mile break in! They checked it out, everything looks ok inside, they are puzzled. What are the odds? Two different installers, two different gearsets, and the same exact noise? They used new pinion bearing, set the pinion depth right and preload, but the noise is worse than ever on coast. I'm ready to go back to my 3.31's and see if that clears it up, I'd rather the 3.73's but the noise is killing me! Could it just be the FRPP gears? (And both sets are not Motive ones). Any help at all would be appreciated, because I'm disgusted, dumbfounded, and my nice, 3 year old car sounds like an old piece of sh*t!! (And I'd really like to stay 3.73 if I could.) Thanks!!

2007Vert

I am having FRPP 4.10 gears installed by Modular Depot in early June. We talked about potential gear whine. They stated that it does not matter what gears you use. The whine comes from a bad install not the gears.

Diabolical!

Bad installs, period. Take it back and make them do it right. Tell them you KNOW what an incorrectly set backlash sounds like.

05 Mustang

+1^^

you should have NO noise what so ever.

mustangtestuser

Did the new lower control arms come before or after the gears? I'm guessing before the gear change.

I'll offer a different opinion. I had my 3.73 gears installed by a Ford Dealer on my automatic and they did not whine. That is, not until I added my Steeda Lower Control Arms. I noticed a slight gear whine on deceleration immediately after the install, exactly like the one you're describing. My gears do not whine under load at any speed. I did a bunch of searches at the time and discovered some other owners with aftermarket lower control arms were complaining of gear whine as well.

My gear whine isn't all that bad, at least, not to me. I asked Steeda and they attributed it to the stiffer bushings transmitting more noise. It made sense to me, since the ride is also rougher and haven't followed up on the issue.

Anyway, I noticed in your signature that you have different lower control arms. Perhaps your vehicle is reacting like mine? Different suspension setups will often translate into increased noise, vibration and harshness that the factory goes to great lengths to dampen. Different aftermarket setups will translated into different noises, different harmonics, etc.

There's also resonance to consider. My G8 GT has a very slight noise that sounds like gear whine at a certain speed. I think it's 68 mph. The TSB says it's actually resonance that has to do with the automatic transmission and has nothing to do with the gears at all. It's too minor to address, so I ignore it. I have to strain to hear it as is.

I'm wondering if going back to the stock lower control arms would help? If anything a soft bushing will mask the noise, which is what softer bushings are supposed to do in the first place, right?

All I can say is before the lower control arms my gears were silent. After the lower controls there was minute gear whine. My experience take it or leave it.

Good luck! I hope that helps!

Simon1

I have had stock gears, FRPP 4.10s and Yukon 3.55's. Stock fell apart and were replaced for free with FRPP 4.10 gear. The 4.10s howled, bad install. 3.55's from Yukon went in with a new locker and the problem was solved.

Setting up a rear differential is an art. Just because someone "knows" how do it by the book, doesn't mean the results will good. The installer for my 3.55s put mine together, drove it, pulled it apart, checked the wear pattern, adjusted, checked the wear pattern, adjusted, drove it and it was good.

modaddict

+1000 to what everyone has already said...

Installation is what matters in gears, not brand name or size at all. Take it somewhere else for next install.