Dinan DIFF noise saga -anyone got any ideas?

[blender]

Greetings.

I'm on my second Dinan 3.91 differential in my '06 Z4MR. The first one lasted six weeks before I nearly went insane . Both differentials exhibit excessive gear noise on Deceleration between 50 and 70 MPH. The problem sounds like a faraway ambulance siren, truck-tire-noise, or gear whine. Unfortunately most of my highway cruising it between 50 and 70 mph.

I needed tires soon anyway so I put four new Falken 452s on the car to ensure it was NOT tire noise. Decent tires by the way It's clearly the Diff and not tire noise.

I can stop it temporarily by increasing then engine RPMs a bit, but that's counter-productive to slowing down. Gear selection doesn't matter.

Link HERE, wait for a recording of the whine.

I've been through the break-in period on two Diffs now, changed the fluid in each of them, and tried Red Line and BMW SAF-XJ fluids. The noise seemed marginally louder with the Red Line fluid if that's possible.

Lastly, the noise volume seems to increase as the diff warms up. After an hour's drive it's damn loud and profoundly annoying. Dinan has been responsive to phone calls but has not as yet provided any solution to the problem.

I'd rather keep the diff since the car runs so well with these gears, but if the noise gets worse it's coming out for unit #3.

I'm spending the money to get the whole trunk lined with Dynamat tomorrow. We'll see what effect that has, if any.

Does Anybody have any ideas on how to kill gear noise from the diff??

regards

rob

[VitaminT]

Does this come as just a ring and pinion set and you have to have it installed or is it a case, R&P, LSD, etc and you just send them the old one.

The noise in the video sounds like a typical loose mesh setup on the R&P. The reason for asking the above question is did you have it installed or does Dinan provide the unit where you basically just bolt it into the car.

[pbdm4k]

Sorry to be a jerk, but you should've bought a Quaiffe.

And Dinan provides it as a prebuilt diff that you just bolt up (there's a core charge), or you can have your own mechanic install the ring and pinion.

[epbrown]

I was wondering what happened with your diff issue. I think I'd have to say the Dinan diffs are duds, or whoever is doing the rebuilds is one - someone on M3 Forum had to get one replaced as well, making 3 of us.

[blender]

I had it installed at a Dinan dealer. It was a full diff swap-out, not a rebuild.

[blender]

And yet, it didn't stop you....
"Be useful, or go away." -Gen. George S. Patton.
------------------------

Originally Posted by pbdm4k

Sorry to be a jerk, but you should've bought a Quaiffe.

And Dinan provides it as a prebuilt diff that you just bolt up (there's a core charge), or you can have your own mechanic install the ring and pinion.

[VitaminT]

Originally Posted by rcleme05

I had it installed at a Dinan dealer. It was a full diff swap-out, not a rebuild.

That sucks. Paid a lot of money for something to be done right and with the highest quality and ended up with garbage. Sounds like they are assembling them at Dinan in about 20min with 'one size fits all' shims.

I am a bit surprised because a good number of guys over on m3forum run their 3.91 diff.

[pbdm4k]

Originally Posted by rcleme05

And yet, it didn't stop you....
"Be useful, or go away." -Gen. George S. Patton.
------------------------

Patton can suck my left nut. Let's quote failed Generals for shits and giggles. Ok! Pfft...

Originally Posted by VitaminT

That sucks. Paid a lot of money for something to be done right and with the highest quality and ended up with garbage. Sounds like they are assembling them at Dinan in about 20min with 'one size fits all' shims.

I am a bit surprised because a good number of guys over on m3forum run their 3.91 diff.

From a business standpoint, it makes the most sense that Dinan is simply reconditioning and rebuilding diffs that they get back from customers and resell them to new customers. Thus the core charge when buying a complete unit. You get a newly rebuilt one, they get yours to rebuild to sell to someone else.

So yeah, maybe the guy assembling them IS a dud. Hope you score a working diff.

[pbdm4k]

Oh... and since Patton thinks I'm useless...

Don't forget you NEED to work in a diff. Find an empty parking lot and start doing figure 8's!
They aren't plug and play. They need to be worked in otherwise it may be causing the whining you're experiencing.

[VitaminT]

I am sure that Dinan takes the "core", uses the returned case, LSD, outputs etc. Probably/maybe uses new bearings, supplies the new ring and pinion, and uses new gaskets. I mean you are paying for a new ring and pinion, the rest is just to make the R&P a nice and easy drop out/drop in package.

If he didn't receive a new LSD then why would he need to do figure eights for the break-in of a new LSD. He isn't complaining of LSD chatter in parking lots and slow tight turns. He is stating he has a whine from the ring and pinion which is what was newly installed and shimmed.

[blender]

Sorry to hear about your problems.

The D773-0460 that we build is the same for the E46 M3 and the MZ4. I have done some research on the two cars regarding the diffs.

In the early development of the E46 M3 diff we sourced the 3.91 gear set from a vendor in the US. We were unable at the time to source any gears for the diff from BMW, this is because BMW does not offer any replacement parts for the diffs other than seals and gaskets. The durability and noise level of the gears sets were acceptable but they could be better.

As the development continued we were able to source the 3.91 gear set from the OE vendor to BMW under BMW's part number for the gear set. This gear set had better than acceptable noise level and durability on par with any OE diff.

When development started on the MZ4 the first thing we did was to install the diff from the E46 M3 into the MZ4. We purchased the car the first month is was available. This was Steve Dinan's personal car he was satisfied with the diff and we offered the diff for sale for the MZ4.

I have checked into the diff part numbers for the MZ4 diffs on BMW's parts catalog and they are different from the M3 even though they have the same case and gear ratio 3.62:1. Since the MZ4 has been in production there has been 2 revisions of the MZ4 part numbers one was in 04/06 and another in 05/07.

There is no technical documentation that I can find regarding why these changes were made so at this point I am speculating that they may have done this to suppress gear noise from customer complaints for one reason or another. The MZ4 has much less sound insulation in the form of isolating noises from reaching the passenger compartment due to the nature of it being a convertible.

When the original 3.91 diff came back from BMW workshop I personally performed the inspection of the diff along with the builder and found no defects in the assembly. The gear pattern was fine on both the drive and coast side of the gears. The backlash and bearing pre load were perfect. We removed the carrier and pinion gear to inspect the bearing and gear faces and both were fine. I do this on every diff that is returned for warranty.

I then located your original diff out of your car from AVUS for the core return and inspected the gear pattern as well. It is also has the same pattern as well as nominal bash lash and bearing preload. We did not disassemble the diff. I then compared the ring gear from your diff to other diffs in our core bank and discovered that the ring gear is different than most of the cores in our core bank. There are about 5 or 6 diffs of about 60 diffs in our core bank that have the same gears as your original OE diff. It is my guess that the gear faces on these diffs have a smoother finish on them to try to suppress gear noise. Visually I cannot tell the difference and I have now way to measure the finish for some type of empirical evidence.

I believe that you do have a gear noise, and from what I can tell it is unacceptable to you. Unfortunately the diff that was inspected under warranty was without defects. I was fine with sending you a replacement diff to try to rectify a potential problem. There is no other 3.91 gear set available to us other than what was installed. Sending your another diff for you to try will not help with the noise.

I have no other alternative than to have your OE diff returned to AVUS and have them reinstall it at no cost to you, and to have them refund you for the full cost of the Dinan diff.

Please contact AVUS for an appointment to have your OE diff installed.

Thanks.

Brian Wright
Tech Support/Warranty
Field service- technical manager

[mimsterzx7r]

Wow I had no idea that the Dinan diff has had issues like this. I was really looking into doing this mod but held off because of the eternal 3.91 vs 4.1 debate. Would polished gears make a difference for this problem.

So what do you guys think? Which way would you go at this point Dinan, Diffsonline, Turnermotorsport? Core exchange vs ring and pinion gear set?

I was researching on the M3 forums and some of the more popular opinons were
1. There is a bit of whine normally from even the stock diff, some diffs more than others
2. Greater whine from improper breakin
3. Greater whine from improper diff fluid
4. Whine is reduced from using polished gears.
5. Of course improper installation.

[epbrown]

Originally Posted by mimsterzx7r

Wow I had no idea that the Dinan diff has had issues like this. I was really looking into doing this mod but held off because of the eternal 3.91 vs 4.1 debate. Would polished gears make a difference for this problem.

So what do you guys think? Which way would you go at this point Dinan, Diffsonline, Turnermotorsport? Core exchange vs ring and pinion gear set?

If OI were doing it again, I'd have a good shop exchange the internals in my original. My chief reason for going with Dinan was ease of install and their reputation made them a known quantity compared to a shop I never heard of. Now, having seen so many of their diffs having issues (my own had to be replaced as well), I'd say you might as well have a reputable shop do the gears and save $1500 or so, since it's a crap shoot either way.

That said, I do love the upgrade - the 3.91 is what the Z4Ms should have come with.

[OG_M3]

Originally Posted by pbdm4k

Oh... and since Patton thinks I'm useless...

Don't forget you NEED to work in a diff. Find an empty parking lot and start doing figure 8's!
They aren't plug and play. They need to be worked in otherwise it may be causing the whining you're experiencing.

you do know that break in procedure has nothing to do with the ring and pinion, but it breaks in the clutch packs that make the diff lock right?

[O-cha]

Originally Posted by pbdm4k

Oh... and since Patton thinks I'm useless...

Don't forget you NEED to work in a diff. Find an empty parking lot and start doing figure 8's!
They aren't plug and play. They need to be worked in otherwise it may be causing the whining you're experiencing.

No you dont, that's for certain (crappy) diffs. AFAIK dinans diffs are just oem with different gearing, so doing figure 8s would be completely useless.


Figure 8s are to work in new (crappy) LSD units to prevent them from wearing uneven in the future.

[blender]

As you may have read above, I got a refund out of dinan along with re-installation of my factory diff. I'm still out of pocket for the three fluid changes, two days of rental car, and $400 worth of Dynamat lining my trunk. That's the price of experience, I guess. Maybe someone else can benefit from my learning experience.

I have arranged with Dan at DiffsOnline to get a take-off set of factory-quiet 3.91 gears from an M5, rebuilt into my Z4M diff. I'll have the gears polished as well for longevity. I'll post a note when those go in about 3 weeks hence.

FYI Dan mentioned he had a selection of near-new factory takeoff 3.85 gears [from the new M3s] at a good price. These would add some kick over 3.62 gears and being factory gears, they *should* be quiet and trouble-free. I guesstimate around 6% more effective torque, 0-60 around 4.7 [ish] seconds.

regards

Rob

[epbrown]

Originally Posted by rcleme05

FYI Dan mentioned he had a selection of near-new factory takeoff 3.85 gears [from the new M3s] at a good price. These would add some kick over 3.62 gears and being factory gears, they *should* be quiet and trouble-free. I guesstimate around 6% more effective torque, 0-60 around 4.7 [ish] seconds.

Interesting that the E90 gears fit, but I can't see why someone would bother. I've read that the 3.91s are no longer in production, so maybe when supplies run out.

[Starscream]

My 4.10's came from Dan's Diff Online and no whine,
I have to admit I have yet to drive with the top up and I might do that tonight to see but I do not hear any difference,
Also I used the SAF-XJ oil,

Just out of interest, Does anyone have a guess as to what the 0-60 and 1/4 mile times would be for a Z4M with 4.10's?

[The HACK]

Add some additional Redline Friction Modifiers to the factory BMW SAF-XJ fluid and the noise will go away.

[epbrown]

Originally Posted by Starscream

Just out of interest, Does anyone have a guess as to what the 0-60 and 1/4 mile times would be for a Z4M with 4.10's?

I was told my Z4M would hit 60 in 4.6 with the 3.91 gears; the 4.10 gears would be 4.8sec or so, due to the additional shift required.

[mimsterzx7r]

Originally Posted by epbrown

I was told my Z4M would hit 60 in 4.6 with the 3.91 gears; the 4.10 gears would be 4.8sec or so, due to the additional shift required.

I have heard this too, the extra shift would take time off your over all 0-60 time, so 3.91 would be quicker in a drag race. But are the 4.10 gears worth it for the extra visceral kick you get form putting more torque to the ground.

[Burt Reynolds]

My 4.10s hit 60 in second gear with ESS software

4.10s are FTW if prioritize peformance over gas mileage and a busier engine.