Z8 HM

I had my 3.91 Dinan differential installed 6 weeks ago by Dinan at their Mountain View shop. From day one, it whined. After two weeks, I complained and they asked me to bring in the car immediately for a day. At the same time as setting up my appointment, they ordered me a new differential and let me know that it would not be in in time for my appointment, but they wanted to check my differential anyway.

After a half day, they returned the car and let me know that I did not have any cover interference problems, and so therefore, that was not the source of the noise. (I think they wanted to check this quickly, so to minimize damage if there were filings in the oil). They asked if I wanted my factory diff back in or if I wanted to stay with the whining diff until the new one arrived. I elected to stay with the 3.91.

Yesterday (3 weeks later), I had the new differential installed, and all noise is gone. The difference is amazing. I am not a rear-end expert, but the following was explained to me. My new differential has an all new gear design. Apparently there is a real art to gear design. There are direct tradeoffs between noise and parasitic loss in the differential. If the gear faces are closer to perpendicular (straight cut), there is less loss, but potential for lots of whining. As the angle becomes less, the gears get quieter, but parasitic losses go up. The trick is to find the optimal point. I can attest that this new gear set is dramatically quieter.

I have been thoroughly impressed with Dinan's service and professionalism throughout this entire process. A class outfit.

Z8 HM

PS They've said no break-in, other than coming back after 1,000 miles.

parkcitytom

GREAT NEWS! I'm due for replacement next week.......and I agree......Dinan has been first class throughout this....

Thanks for sharing!

__________________
Tom


Park City Utah, @7,225 Feet In The Rockies

2006 E60 M5
Pictures and Videos at: M5s.us

Silver Gray Metallic - Silverstone Ext Leather - Aluminum
Charcoal Filters: Out - Tint: Ceramic 50% / 20% - Bra
iBrights 2.0 (White) - V1 Hard-Wired
Dinan: Exhaust - Stage 2 Suspension - CF Front & Rear Braces - Wheels - 3.91 Limited Slip
Dinan: Pedal Cover Set - Throttle Bodies (Paid For, Awaiting Installation)
EvoSport: Headers - Power Pulley Kit - Stage 2 ECU Upgrade (Waiting To Order)

canysmc

Did Dinan say:

Whine is totally eliminated?

And any possibility of hearing any whine at all?

__________________
20XX M5 Its Got To Be Red
2008 328i Vert Crimson Red/Brown
1996 Porsche 993TT Iris Blue/Grey
2007 Ducati Monster S4RS Testastretta
2005 Ducati S2R
2007 Aprilia Sportcity 250ie
2009 Aprilia Sportcity One 125

2007 Mini Cooper S Vert Sidewalk Package Sparkling Silver/Malt Brown
2006 750Li White/Brown
2006 M5 Indianapolis Red/Indianapolis Red
2001 M5 Imola Red/Black/Imola Red
The Mercedes Benz/Range Rover Years
1992 Miata Red/Black
1987 535is Blue/Beige
1987 930 Black/Black
1985 535i White/Black
1985 911 Black/Black
1972 911 Blue/Black

EuroCarFan

Good to hear your positive outcome. I talked to my sales guy there today and it looks like they're on back order so I'll wait.

__________________
2006 M5 Blk/Blk/Alum Fully Loaded
Engine: ESS/RPI Stage 2 Tune | RPI Ceramic Coated Headers + GTS Exhaust w/Gloss Black Tips and Red RPI Logo + Ram Air Scoops + BMC Filters + Block-Off Plates + Pulley + Oil Cooler | Sprint Booster V2 | Euro SMG LC Tune
Wheels, Susp & Brakes: Neez QD7s Hyper Black 20x9-10 | PS2s | KW V3s | Dinan FRC + Rear Sway Bar + Front & Rear CF Strut Braces | Brembo 380mm BBKs
Exterior: Revozport CF Splitter | Hamann Replica CF Roof Spoiler | Vorsteiner CF Trunk Spoiler | Hartge Diffuser | CF Lower Mirror Covers | CF Side Gills | 3M Clear Bra
Interior: RDSport Alum Pedals | Hardwired V1 | iPod Integration Kit | BSW Stage 1 Speakers | Flat Bottom Steering Wheel w/CF Trim | AS Designs Red Tachometer
Lighting: Eurospec Headlights w/Clear Corners | LCI LED Taillights | Trinity Autosport 5W AEs | Trinity Autosport Interior LEDs
Coded Options: Folding Side Mirrors, Windows and Moonroof w/Remote | Deleted "Accept" Screen | Turn Signals in HUD | Real Speed in OBC Screen | Automatic Heated Seats Controls in iDrive

905RMP32V1x

That doesn't make sense. How could I have one of the first diff's and it not whine? Is there that much variabilty in the gear angle/set-up from diff to diff so that some of them whine and some don't? Is there now a new "quality control" regarding the angle to optimize performance and minimize whine. I'm happy they worked it out though.

__________________
2006 Indy Red/Blk/Alum loaded,
H&R springs w spacers, 167(M6) wheels,
Dinan 3.91, Evo Pulley
CF grills, CF vents, ACS Spoiler
Vorsteiner CF Vented Hood, CF lower steering wheel
905R-driver
MP32-irons
ProV1x-ball

parkcitytom

This is from a post of mine on the same subject:

We are still a fews days out for the replacement of the differential, but my SA, who is clearly an M Fan-atic.......offered HIS opinion on what's going on with these things.....he offered his opinion after a lot of back-and-forth with Dinan. That said, and for what its worth, he thinks it has to do with something called "backlash" being set too tight....causing the gears to whine as they warm up and pressure between them increases. I do recall that the whirring was not there when the car was cold...

So if (and yes, its a BIG if) this is an assembly problem, it makes complete sense why one differential made right after another one will whine while the first one doesn't. While no one knows for sure at this point, this fits the symptoms: The only apparent difference between these things is how they are put together.....the gears, covers, and dealer installation practices all seem to have been eliminated as the cause.....the Human Factor of strict adherence to assembly specs seems to be the next potential suspect in line....

That said:

We are all car nuts to one degree on another, and we want to know everything about everything about everything, in detail, in triplicate.......but as a simple consumer, you can't ask for better service......no questions asked, a loaner for as long as it takes......frequent updates to keep me posted, etc....I won't go as far as to say its been enjoyable, but I have A LOT of awful stories about car dealers and service.

LilBadM

The Dinan diffs no longer have a whine, as there was a clearance modification done to the diff cover that was causing this whining noise. It is also very important that the dealer tightens the diff cover bolts in the correct order with the correct amount of torque, or this can also cause a gear whine. We are going to get a chance to drive ours next week on Tuesday with all the Dinan upgrades done.

__________________
S85 DINAN S3R Silver Grey - Beast
S54 M Coupe Pheonix/Black - rare bird
S52 M Coupe Estoril/Estoril - show queen



GO Fast: Dinan 5.8 stroker, Dinan 13% crankshaft pulley, Dinan middle racing with 4" resonators, Dinan exhaust, Dinan air mass meter/intake, Dinan throttle bodies,
Dinan stage 3 software, Dinan CF F & R strut tower brace, Dinan stage 2 suspension, custom headers Fabspeed 200 cell race cats

Exterior: Brembo 380mm 6 piston front & 4 piston rear yellow Calipers, HRE P40 Forged Monoblock Gloss Black / Machined Face 19x9 ET9 19x10.5 ET29
Michelin PSS's, BMW Performance Gloss black kidney grills, Gloss black side grills, Trinity Autosport 3W Angel Eyes, smoked LED side markers, Euro LCI led tails.

Interior: Alcantara shift & E- Brake Boot, Black anodized "M" pedals, OEM Nappa Steering wheel

DinodealM5

That's great News Z8 HM...I'm dropping my beast of in the morning to have my whining dinan diff replaced with the modified one. Thanks for sharing.

__________________
DINODEALM5
2006 BMW M5 ALPINE WHITE
2005 MB G500 ALABASTER WHITE
2007 CORVETTE Z06 MACHINE SILVER

andrewsherman

My car is going in in about an hour to have the dif installed. Crossing my fingers.

__________________
'07 M5: Silver Grey/Black Full Merino Leather|Walnut Madeira Wood Trim|HUD|Sirius|Comfort Access|Split Rear Seats|Rear Sunshades|iPod Interface|

Goodies: ESS Software|Dinan 3.91 Rear Differential|EvoSport Pulley|Dinan Free Flow Exhaust|Dinan Front Control System|Dinan Rear Sway Bar|RPI Ram Air Scoops|BMC Filters|RPI Oil Cooler|SprtintBooster| HRE P40s in Graphite|LED Tail Lights|AngeliBright 3.0|AC Schnitzer Roof Spoiler|Vizualogic A-1250 Rear DVD Sysyem|Huper Optik ceramic tint|clear-bra|V-1 Stealth Install|Blinder M-40|Aluminum Pedals|LED interior bulbs|OE M6 style wheels w/Blizzak LM-22 255/40VR19 (Winter Set up)

Past Rides: '04 745Li Titanium Grey/Black|'01 740iL Titanim Silver/Black|'91 K1100RS|'88 K75S

Z8 HM

Sounds like there may be mutiple problems out there. I am sure that I had no cover clearance problem. 3 weeks ago, when I brought the car in, that was the first thing they checked. Also, my whine was only on deceleration or moderate load cruise. It was not present with acceleration. I can't imagine that a noise as loud as I heard, consistently, was due to interference with a differential cover. If all it was was the cover, they would have fixed it 3 weeks ago and saved themselves the trouble of ordering and install a whole new differential.

Then there is the backlash/adjustment vs gear design question. I clearly had to wait for some new part or procedure to be put in place before this "new" differential was available. The head of Dinan Mountain View specifically told me that I got a differential with a new gear design. It may be possible that an "old" gear design could be quiet with the right backlash adjustment, but I am suspicious that if that were the case, they would have pulled my differential and reworked it to solve the whine. Instead, they waited until they had a new design.

The only explaination I can come up with for the mix of whining diffs and non-whining diffs out there so far is that perhaps there are multiple manufacturers of the gears used ( I think an earlier post referred to BMW gears and a new design both being used). My original differential was certainly a later install (done in March), so perhaps Dinan had run out of the original gear sets and was using a new supplier?

In my amateur sleuthing on gear whine and differentials, I also found papers that indicated that noise (and parasitic loss) can be caused by the type of surface that the gears have. You can specify micro-polished surfacing (which is quiet but expensive) for instance. This leads me to believe that if Dinan's spec to their suppliers was loose on tolerances for surfacing, they might have gotten some variabilty there, and that was the source of noise.

Only Dinan really knows what is going on, as they clearly will have the serial number of each differential installed, the supplier used for the components, and the assembly procedure used to put the differential together. They can take all that data and correlate it with "whining".

I don't mean this to be critical of Dinan at all. As a business, they probably want to avoid a mass recall. So, they have adopted a policy that says if the customer is unhappy, fix it asap. Otherwise, leave it alone. I think that's smart business.

Z8 HM