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M3 Cougar
Sat, Jan-29-2005, 12:40:03 AM
I just picked up my car from having the rear end diff upgraded to the 3.91 and was surpised to learn that there is a 1200 mile breakin period. Is this standard with diffs? I was really looking into jumping on it too! :banghead:

FLGHTM34U
Sat, Jan-29-2005, 01:05:14 AM
I just picked up my car from having the rear end diff upgraded to the 3.91 and was surpised to learn that there is a 1200 mile breakin period. Is this standard with diffs? I was really looking into jumping on it too! :banghead:
i dont know about the diffs but i had that recall on the bearings and there was a breakin period. Also coug was wondering how do u like the dinan mods on your car, do u see a big difference.

M3 Cougar
Sat, Jan-29-2005, 01:42:15 AM
i dont know about the diffs but i had that recall on the bearings and there was a breakin period. Also coug was wondering how do u like the dinan mods on your car, do u see a big difference.

I've been very happy with the Dinan products. Although most on this board will tell you they are over priced and do nothing! :agree:

Divexxtreme
Sat, Jan-29-2005, 02:48:20 AM
Who told you there was a break-in period for a differential? It's BS....

ArtM3
Sat, Jan-29-2005, 02:57:26 AM
I don't know if you need to nurse it, but you may want to change the fluid to get rid of any machining scap, wear in shavings, etc.

M3 Cougar
Sat, Jan-29-2005, 03:29:16 AM
Who told you there was a break-in period for a differential? It's BS....

The service tech said I couldn't do more than 75% of full power in any gear and that after 1200 miles I needed to bring it back in to have the fluid changed. They also specified this on the paper work and made note not to floor it or "kick start" it whatever that means.:nixweiss:

Divexxtreme
Sat, Jan-29-2005, 04:11:31 AM
Must be a Dinan thing (not being sarcastic)..I've never heard of that before.

Will Pwr
Sat, Jan-29-2005, 04:15:34 AM
Must be a Dinan thing (not being sarcastic)..I've never heard of that before.

I second that.....

usually I have "broken-in" rear diffs by doing slow figure 8's for 15mins or so... :nixweiss:

Duck360198
Sat, Jan-29-2005, 06:23:21 AM
I just picked up my car from having the rear end diff upgraded to the 3.91 and was surpised to learn that there is a 1200 mile breakin period. Is this standard with diffs? I was really looking into jumping on it too! :banghead:

I have a 1200 mile breakin period for my rod bearing recall

M3 Cougar
Sat, Jan-29-2005, 02:33:55 PM
I second that.....

usually I have "broken-in" rear diffs by doing slow figure 8's for 15mins or so... :nixweiss:


That was good! :rofl2: :rofl2: :rofl2: :rofl2:

Divexxtreme
Sat, Jan-29-2005, 03:57:23 PM
He was being serious. That's normally all that's needed.

That was good! :rofl2: :rofl2: :rofl2: :rofl2:

daveeddie
Sat, Jan-29-2005, 10:39:13 PM
Take a look in the owners manual. My 2003 owners manual states that the break-in period applies to the engine and the differential. I also had the Dinan 3.91 differential installed and was instructed to follow the break-in period requirements.

Divexxtreme
Tue, Feb-01-2005, 02:44:37 PM
The break-in requirement for the rear diff when you get your car is for the variable M- LSD...not for the R&P. If you simply get a new R&P, there should be no break-in period.

M3@NYC
Tue, Feb-01-2005, 03:54:23 PM
Take a look in the owners manual. My 2003 owners manual states that the break-in period applies to the engine and the differential. I also had the Dinan 3.91 differential installed and was instructed to follow the break-in period requirements.


I am planning on getting this mod. I think the 4.10 diff might be too much for me. How do you like the 3.91? can you feel any gains?

anerbe
Tue, Feb-01-2005, 09:03:56 PM
The service tech said I couldn't do more than 75% of full power in any gear and that after 1200 miles I needed to bring it back in to have the fluid changed. They also specified this on the paper work and made note not to floor it or "kick start" it whatever that means.:nixweiss:


75% of power in first gear should be the max.....as the gear increases, torque to the diff decreases, so I'm assuming that the dealer means 75% max power to rear diff in 1st gear unless the dealer is wierd or something

M3 Cougar
Wed, Feb-02-2005, 12:04:49 AM
I am planning on getting this mod. I think the 4.10 diff might be too much for me. How do you like the 3.91? can you feel any gains?

Since I'm waiting for the 1200 miles I haven't jumped on it yet but will let you know when I do. I did take a drive to College Station today so I only have 850 miles left to go! :wave:

daveeddie
Wed, Feb-02-2005, 03:30:17 AM
I am planning on getting this mod. I think the 4.10 diff might be too much for me. How do you like the 3.91? can you feel any gains?

I like it a lot. I am still in the break-in period; however, there is a noticeable improvement in sub-5000 RPM acceleration.

daveeddie
Wed, Feb-02-2005, 03:40:25 AM
The break-in requirement for the rear diff when you get your car is for the variable M- LSD...not for the R&P. If you simply get a new R&P, there should be no break-in period.

The owner's manual also states that the break-in procedures should be followed when the differential is replaced. Is this just BMW being conservative?

Divexxtreme
Wed, Feb-02-2005, 04:06:32 AM
The owner's manual also states that the break-in procedures should be followed when the differential is replaced. Is this just BMW being conservative?


If you get a new differential, then you get a new variable M-LSD...hence the break-in requirement. If you simply change you ring and pinion, then there should be no need for break-in. It sounds like Dinan replaces the entire differential with a new variable M LSD plus 3.91 ring and pinon, which is why they require a break-in. I'm not sure though..but that what it sounds like.