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Discussion Starter · #1 ·
I'm looking at dropping down to something more spritely for in gear shove for the OZ M5 in the near future.
The US M5 runs 275/30/19 and the OZ M5 Ute runs 275/30/20.
the difference is that the OZ car is about 4% longer legged then the US M5 just in wheel specs I mentioned.
If I also add the 3:45 to the ute the only difference will be in the taller rubber, so not much (only that 4%)

Now my question is can/has anybody just bought the different gear set for their M5's and had it fitted at a specialist shop?
If so what are the pro's cons of this move.
Much less total cost up front, but am I missing something here?

diffsonline.com - Custom Geared BMW LSD Differentials

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Apples
 

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I'm looking at dropping down to something more spritely for in gear shove for the OZ M5 in the near future.
The US M5 runs 275/30/19 and the OZ M5 Ute runs 275/30/20.
the difference is that the OZ car is about 4% longer legged then the US M5 just in wheel specs I mentioned.
If I also add the 3:45 to the ute the only difference will be in the taller rubber, so not much (only that 4%)

Now my question is can/has anybody just bought the different gear set for their M5's and had it fitted at a specialist shop?
If so what are the pro's cons of this move.
Much less total cost up front, but am I missing something here?

diffsonline.com - Custom Geared BMW LSD Differentials

Got comments?
Apples
Stuart,

There have been a few members that have had interaction with diffsonline and have been very happy. There are a couple of threads on the board regarding the gearing that they went to. There are a couple that also did the DINAN diff upgrade. Good luck and let us know what you go with. Here's one thread about diffsonline.
 

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I'm looking at dropping down to something more spritely for in gear shove for the OZ M5 in the near future.
The US M5 runs 275/30/19 and the OZ M5 Ute runs 275/30/20.
the difference is that the OZ car is about 4% longer legged then the US M5 just in wheel specs I mentioned.
If I also add the 3:45 to the ute the only difference will be in the taller rubber, so not much (only that 4%)

Now my question is can/has anybody just bought the different gear set for their M5's and had it fitted at a specialist shop?
If so what are the pro's cons of this move.
Much less total cost up front, but am I missing something here?


diffsonline.com - Custom Geared BMW LSD Differentials

Got comments?
Apples
You can simply swap the gearsets.

Our cars have the "big" diffs ( I think referred to as 210 internally) so not all gearsets are swappable. There is lower cost since you don't need the casing (usually referred to as the pumpkin), but you do have the down time of pulling the original diff, sending yours out, having it opened, checked while open and swapping out the parts, then returning. You should measure the cost (and some down time) vs. the cost of getting a used diff that has been rebuilt be a reputable diff builder to your specs, and subtract the cost of what you can sell the original (I assume stock here) diff for.

I got an entire pumpkin done because I made some other changes at the same time and didn't want the down time. I also kept the stock diff for a while to see if I liked the changes. Once I knew I did, the stock diff got sold.

Generally speaking, it will be much cheaper to simply swap the gearsets. Other than lost time, I can't really see much downside to just swapping gearsets.

Regards,
Jerry
 

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Yes.. a number of guys have done it. Personally I went for the Dinan 3.45 set up as I got a great deal on the entire diff brand new. It only cost me $2k for the Dinan and I sold my OEM diff for $900... the direct swap was a piece of cake. kinggf Swapping the gears themselves is a bit more difficult for DIY application. I love the 3.45 on a NA beast and would probably love it on a blown S62 as well.
 

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in the nissan world, you can go to the dealer with the ring & pinion part number(s) and order up exactly what you need. Is this the same? Or do you need 2nd-hand parts for this swap?
 

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Who is Scott? :eek7:
 

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in the nissan world, you can go to the dealer with the ring & pinion part number(s) and order up exactly what you need. Is this the same? Or do you need 2nd-hand parts for this swap?

I am almost certain you cannot source the 3.45 ring and pinion from BMW parts, I think you can only source the entire differential. I know the more aggressive 3.62 ratio is only available from old school '80's model 6 and 7 - series if i remember correctly.

I sourced my 3.62 gear set from Dan with diffsonline.com and did the swap myself. Total cost of all the necessary parts was $550.

I got alot of info from the guys at metricmechanic.com and they shed some light on how precise the tolerances were for setting up these differentials correctly; much more precise than the usual domestic differentials. So that being said, i wouldn't recommend attempting a swap without some experience and the proper measurement tools and specifications.

There have been several members, including myself, that have posted there opinions and reviews of the different gear ratio's. I would read them before selecting a particular ratio.

Additionally, if you have the extra money to spend, its a good idea to consider rebuilding the stock LSD or upgrading while you have the diff apart.

Have fun.
 

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I got my 3.62 gear set from Dan @ diffsonline. Great guy, wonderful to deal with. I did the work myself and currently have 4k on the new gears with no problems. If you have the know-how, or know someone that does, I do recommend it!
 

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Discussion Starter · #14 ·
From the time the diff box lob's at your door how much time would it take to fit the gears and drive off?
Just wondering if I take the gear set to a shop what labour charges might be additional to the gears/parts.
How big are the parts, as US Postal has the flat rate boxes and they go international.

I see a few guys with the 3:62 on the board, do you find yourself working the gears a bit too much just to et up to speed?
I've got the 3:45 in the US car and I find that about a short as i'd want...going to a 3:62 I'd be banging through 3 gears to just hit 60.
Especially if you've gone with a SC set up...tire fry with that combo.

Anybody got a site that does speeds for a combo of wheels size and diff ratio's
I can find "rim tire 1 V's rim tire 2 comparo sites, but nothing that lets you add diff to the equation.

Apples
 

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Discussion Starter · #15 ·
I did some math ages ago on what speed the car should be turning at 1,000rpm increments.
When I put in the tire and diff numbers in the bimmerworld diff/gear ratio calculator, it seems to come up with pretty different numbers to what my GPS says.
Good math doesn't lie, and either does a GPS. hmmm

I did a search just now and found a page that lets you add gear ratios and a RPM (I used 7,000 max) and then the diff ratio you want to see.
Running the numbers on that program it seems to show that a 3:63 on 275/30/20 will give me just slightly less speed at a given RPM v's the 3:45 on 275/30/19, so basically the same.

Knowing this I might do the 3:63 on the 20's if I'm going to get the squirt power in the 2,000 - 5,000rpm range that the 3:45 gives me here on the 19's

Apples
 

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Discussion Starter · #16 ·
Anybody know the weight size of the gear set kit?
Plus what comes in the kit.
I'll be heading back to OZ in late Sept, so I'll probably take it back with me.
Apples
 

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