New Dinan 3.91 Rear Diff ?

JDS M5 · 24th February 2007, 21:56

Recently, I had the Dinan exhaust and the 3.91 Rear Diff. installed. I love the sound of the exhaust, and I'll have to wait to comment on the Diff. until the breakin is complete and Diff. oil changed. Maybe it is my imagination, but I do hear a slight whine at speed after you take your foot of the gas. Is this normal, and will it go away? Has any one else experienced this slight noise, is it a matter of waiting for breakin to be completed. Any thoughts, Please.

Regards,

JDS M5

bonehead · 24th February 2007, 22:00

Search it my friend. A well known and unfortunate problem that will not go away with break-in.

parkcitytom · 25th February 2007, 02:10

Quote:

Originally Posted by JDS M5

Recently, I had the Dinan exhaust and the 3.91 Rear Diff. installed. I love the sound of the exhaust, and I'll have to wait to comment on the Diff. until the breakin is complete and Diff. oil changed. Maybe it is my imagination, but I do hear a slight whine at speed after you take your foot of the gas. Is this normal, and will it go away? Has any one else experienced this slight noise, is it a matter of waiting for breakin to be completed. Any thoughts, Please.

Regards,

JDS M5

I have the same 3.91 diff...yes it has a distinct "whirring" noise only when my foot is off the gas. I am also in the middle of the break in period. A few threads here suggest that the oil change will fix the problem.....but I'm not holding my breath...

Tom

LI-M5 · 25th February 2007, 18:54

i got the diff for a while now and i got the whine , just waiting for dinan to replace it now !! when did you get it installed ask the dealer if they had it in stock for a while cause dinan supposedly fixed the problem.

parkcitytom · 25th February 2007, 20:52

Dinan was out of cores, so I had to send mine in and to have them build it...perhaps three weeks ago...the whirring is there....the only hope is the oil change, but thats really iffy IMO.

Tom

andrewsherman · 25th February 2007, 21:17

I thought this was fixed. I have one on order, but now I may hold off.

kinkade · 25th February 2007, 21:18

I am somewhat concerned, i have on order a new diff from Dinan and was assured that the new units don't "whine". This problem i'm told started after Dinan ordered gears from BMW. Are the problems that have arisen on new units? Hopefully someone from Dinan will read these posts!!!

parkcitytom · 25th February 2007, 21:25

If you do a search on this, you will find that its about an even split between those that lost the whirring when they changed out the diff oil @1,200 miles.....and then those that have had and still have the whirring.

It is slight and cannot be heard with the radio on at almost any level.....but when "silent running" you can certainly hear it....always and only under acceleration, at any level.

Tom

JDS M5 · 25th February 2007, 22:05

My 3.91 Diff was installed last Friday, Feb. 23rd. The guy from Fall-Line took it for a ride and said everything was OK. On my way home, I would lift off the throttle and hear this slight whining sound. It was repeatable every time. I.E. traveling at 70 MPH, I removed my foot from the throttle, and for the first 10 sec. I would hear the noise and it would then fade, I would accelerate again, and then lift off, and again I would hear the noise, which would then fade away. Is this what happened to everyone else, or was your noise different. Does anyone have a number or contact to call at Dinan. You should not have this problem for $3000. How can you tell if the serial number of the unit installed has an issue with the gear set??

Regards,

JDS M5

Quote:

Originally Posted by LI-M5

i got the diff for a while now and i got the whine , just waiting for dinan to replace it now !! when did you get it installed ask the dealer if they had it in stock for a while cause dinan supposedly fixed the problem.

Gustav · 25th February 2007, 22:15

Did you read this:

Important update.

I have just got an mail from Steve Dinan himself, after I e-mailed them in general. Dinan is a Sponsor of m5board.com and m6board.com.

I quote below:

"We ran out for a short period of time so we purchase 14 gears from BMW Motorsport. These are the ones that made noise. We now have our gears on the shelf and would be happy to warrant the differential for anyone who is having a noise issue. The BMW gears are good quality they are just louder than ours. Our gears are lapped so they are quite. This basically means we run the gears against each other with lapping compound. This polishes the gears and reduces friction and noise. "

End of quote.

So for you people who have issues: contact Dinan, send them regards from Gustav and m5board.com and refeer to this thread if anything is unsure. That is if you want Dinan differentials instead if BMW M GmBh ones

I hope this helps!

/ Gustav
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