DINAN 3.91 Limited Slip Differential initial impressions & review

ykjones · 19th March 2012, 05:57

After doing months of combing the forums and seeking the wise counsel of my trusted mechanics, I recently purchased and had installed the DINAN 3.91 Limited Slip Differential by the fine folks at Autohaus Frankfurt in Murrieta, CA. I am simply in awe of the improvement in low end torque and acceleration. As awesome as the M5 is, I like many, always felt that it was lacking in the low end torque department. Upon leaving the shop with it newly installed, I was like "wow, now this is special". This was in P400 mode too, no M button, no S5 or S6 or DSC off either and I was so impressed. As you can imagine I just had to press my M button just to see what it will feel like and man the beast is a whole another animal now! It is just amazing and I'm enjoying the car to a whole new level now and nearly all of my driving thus far for the break in period has been in P400 mode. As another member noted in a earlier review, P400 mode feels like P500 and press the M button, it's really insane now. When I backed into the garage like I normally do when I got home, I no kidding almost drove through the garage and into the house as I had forgotten I had the diff in and all the extra torque! That was one of the eye opening moments for me thus far. There is definitely a noticeable increase in torque and acceleration. Just in P400 mode around town it just so effortlessly pulls away now. Just doing a little drive around some little twisties near where I live, I couldn't believe how enjoyable it was in P400 mode when I would normally have the M button pressed. The tough part now is the 1200 mi break in period which consists of basically no WOT, and nothing over 5500 RPM's or 105 mph. Just pretty much taking it easy. My mechanics did recommend that the more turns, the better for helping breaking in the diff. It's actually kind of funny cruising around town just trying to put some miles on it so I can get those break in miles in. After 1200 mi you go back and get the diff fluid flushed and replaced with BMW's special diff fluid and then you can really go have some fun. So I'll follow up with another review after I get past the break in period. I, like many, give a lot of thought and do a lot of research before I do any performance mods for my M5. I can (so far) attest with DINAN stating that the 3.91 diff is the best bang for the buck mod for improving immediate acceleration for the M5. Now it's off to finish getting in my break in miles (1095 mi more) before MFest VI in Vegas on Apr 20!

C's Bimmer · 19th March 2012, 06:15

I've been strongly considering this modification for a long time. Neil (LI-M5) always tells me this is the one mod I am missing and I think he is right. I'm really curious to hear your review after the 1200 mile break in. Keep us posted!

AngelSlayer · 19th March 2012, 06:28

Do you hear any whining from the diff? There were a lot of complaints about a whining noise which is the main reason I haven't done this.

kendall993 · 19th March 2012, 06:37

Quote:

Originally Posted by AngelSlayer

Do you hear any whining from the diff? There were a lot of complaints about a whining noise which is the main reason I haven't done this.

I have the same diff and I don't really notice the wine. I think that complaint is over blown.

AngelSlayer · 19th March 2012, 06:41

Quote:

Originally Posted by kendall993

I have the same diff and I don't really notice the wine. I think that complaint is over blown.

Hmm... I guess I'll need to find someone so I can hear it in person. Hopefully you're right and it's over blown.

yk, thanks for the review!!

ykjones · 19th March 2012, 06:44

Quote:

Originally Posted by AngelSlayer

Do you hear any whining from the diff? There were a lot of complaints about a whining noise which is the main reason I haven't done this.

No hint of any wine whatsoever. Perfectly quiet and no issues thus far.

khyber · 19th March 2012, 06:46

Quote:

Originally Posted by AngelSlayer

Do you hear any whining from the diff? There were a lot of complaints about a whining noise which is the main reason I haven't done this.

From my understanding Dinan used a different manufacturer for the internal of the diff which causes the whine but that issue as been rectified. Gustavs post on the issue down below!

Thanks for the review YK!

Quote:

Originally Posted by Gustav

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
______________

ACG · 19th March 2012, 06:58

Do you have a pre dyno as I would like to know what kind of trq you gained from this mod. Like John said I have kept my distance due to the compliants of the whine but if you can let us know after the break in period has been complete that would be great.

IndyRedBeast · 19th March 2012, 07:14

i'd really like to drive one and see the differences, its not a cheap mod to experiment with.

Fiftytwoeighty · 19th March 2012, 07:19

Quote:

Originally Posted by ykjones

After doing months of combing the forums and seeking the wise counsel of my trusted mechanics, I recently purchased and had installed the DINAN 3.91 Limited Slip Differential by the fine folks at Autohaus Frankfurt in Murrieta, CA. I am simply in awe of the improvement in low end torque and acceleration. As awesome as the M5 is, I like many, always felt that it was lacking in the low end torque department. Upon leaving the shop with it newly installed, I was like "wow, now this is special". This was in P400 mode too, no M button, no S5 or S6 or DSC off either and I was so impressed. As you can imagine I just had to press my M button just to see what it will feel like and man the beast is a whole another animal now! It is just amazing and I'm enjoying the car to a whole new level now and nearly all of my driving thus far for the break in period has been in P400 mode. As another member noted in a earlier review, P400 mode feels like P500 and press the M button, it's really insane now. When I backed into the garage like I normally do when I got home, I no kidding almost drove through the garage and into the house as I had forgotten I had the diff in and all the extra torque! That was one of the eye opening moments for me thus far. There is definitely a noticeable increase in torque and acceleration. Just in P400 mode around town it just so effortlessly pulls away now. Just doing a little drive around some little twisties near where I live, I couldn't believe how enjoyable it was in P400 mode when I would normally have the M button pressed. The tough part now is the 1200 mi break in period which consists of basically no WOT, and nothing over 5500 RPM's or 105 mph. Just pretty much taking it easy. My mechanics did recommend that the more turns, the better for helping breaking in the diff. It's actually kind of funny cruising around town just trying to put some miles on it so I can get those break in miles in. After 1200 mi you go back and get the diff fluid flushed and replaced with BMW's special diff fluid and then you can really go have some fun. So I'll follow up with another review after I get past the break in period. I, like many, give a lot of thought and do a lot of research before I do any performance mods for my M5. I can (so far) attest with DINAN stating that the 3.91 diff is the best bang for the buck mod for improving immediate acceleration for the M5. Now it's off to finish getting in my break in miles (1095 mi more) before MFest VI in Vegas on Apr 20!

I love my Dinan 3.91. You will be spinning well into 2nd looking for traction.

Let me know if you want to do some WOT with my broken in 3.91. I have to make a run out to Temecula this week to see my CPA.

~Woody