Differential Ratio

[IronZ4M]

planning to change Differential Ratio with my mods any advice and what is the best one to buy?

[epbrown]

If you're buying the ring and pinion gears to have them installed in your existing diff, you can shop buy price - everyone sells the same part.

[IronZ4M]

Originally Posted by epbrown

If you're buying the ring and pinion gears to have them installed in your existing diff, you can shop buy price - everyone sells the same part.

I made a search and I found a ring with the pinion gears to be installed in my existing differential but I would buy a whole 3.91 diff I dont want to disassemble my OEM differential If I had the chance to buy a whole one. Is there anybody selling it ready to be installed (Whole 3.91 diff.)

[epbrown]

All of the major tuners do: Hamann, Hartge, AC Schnitzer, Dinan, and they all charge a premium for it - about double what it would cost to have your diff rebuilt with the new gears. Supposedly the advantage is quality control, but in my experience there is none - the Dinan diff I bought had to be replaced immediately due to poor rebuild quality by whoever they outsource the rebuilds to and I wouldn't be surprised to here the other tuners do the same; we're eyeing the second diff as it makes an intermittent grinding noise.

If I were doing it again, I'd simply have a local shop with BMW experience do the work and save the money. In fact, if it worsens next year out of warranty, I'll simply have it re-done by someone competent.

[Diokaef]

Originally Posted by epbrown

All of the major tuners do: Hamann, Hartge, AC Schnitzer, Dinan, and they all charge a premium for it - about double what it would cost to have your diff rebuilt with the new gears. Supposedly the advantage is quality control, but in my experience there is none - the Dinan diff I bought had to be replaced immediately due to poor rebuild quality by whoever they outsource the rebuilds to and I wouldn't be surprised to here the other tuners do the same; we're eyeing the second diff as it makes an intermittent grinding noise.

If I were doing it again, I'd simply have a local shop with BMW experience do the work and save the money. In fact, if it worsens next year out of warranty, I'll simply have it re-done by someone competent.

Evosport don't really have the problems dinan and other have. I would contact them and see what they offer

[inTgr8r]

http://www.diffsonline.com/is another choice that has been recommended by others.

[BTM]

If you're asking which ratio to go with, 3.91 and 4.10 are the most popular. I have no personal experience with either, and opinions seem to differ.

[mfanatic325]

If you're already out of warranty coverage, then go for diff upgrade. Depending on our budget, either obtain the ring & pinion & get your own diff rebuilt, or buy a whole new diff to swap in.
If you go with a rebuild, make sure a reputable shop (i.e. has rebuilt this exact same differential before) does the work/labor. Rebuild labor alone should be around $1k, including fluids, etc.

As for ring & pinion, you can find them as cheap as $450 a set if you're lucky. Most buy new though, so you're looking to pay a slight premium, in the ballpark of $800 or so.

If parts and/or labor rates are good, then I say go for it. If not? I say stick with OEM diff. The performance increase is definitely noticeable, but not necessarily worth the money.
^Again, depends on costs/rates.

[IronZ4M]

Originally Posted by mfanatic325

If you're already out of warranty coverage, then go for diff upgrade. Depending on our budget, either obtain the ring & pinion & get your own diff rebuilt, or buy a whole new diff to swap in.
If you go with a rebuild, make sure a reputable shop (i.e. has rebuilt this exact same differential before) does the work/labor. Rebuild labor alone should be around $1k, including fluids, etc.

As for ring & pinion, you can find them as cheap as $450 a set if you're lucky. Most buy new though, so you're looking to pay a slight premium, in the ballpark of $800 or so.

If parts and/or labor rates are good, then I say go for it. If not? I say stick with OEM diff. The performance increase is definitely noticeable, but not necessarily worth the money.
^Again, depends on costs/rates.

to rebuild my diff. for sure will be cheaper for me but I'm just worry if I bought the ring & pinion and get them to the shop then having a trouble with it after installing it due poor rebuild I just wanna buy a new diff and swap it in.

For a new diff. builded already how much roughly it costs? what is the Ratio difference between 3.91 and 4.10?

Originally Posted by inTgr8r

http://www.diffsonline.com/is another choice that has been recommended by others.

I've checked that. Are they making the build with the hosing or shell I use my diff.?

Originally Posted by epbrown

All of the major tuners do: Hamann, Hartge, AC Schnitzer, Dinan, and they all charge a premium for it - about double what it would cost to have your diff rebuilt with the new gears. Supposedly the advantage is quality control, but in my experience there is none - the Dinan diff I bought had to be replaced immediately due to poor rebuild quality by whoever they outsource the rebuilds to and I wouldn't be surprised to here the other tuners do the same; we're eyeing the second diff as it makes an intermittent grinding noise.

If I were doing it again, I'd simply have a local shop with BMW experience do the work and save the money. In fact, if it worsens next year out of warranty, I'll simply have it re-done by someone competent.

I dont like Dinan products they always has troubles and they cost alot . other tuners Ac, Hartge etc they are so good but they would cost alot also

[IronZ4M]

Originally Posted by Diokaef

Evosport don't really have the problems dinan and other have. I would contact them and see what they offer

Evosport doesnt have a diff product for the Z4 M. is the M3 has the same diff. as the Z4 M? as far as I know the Z4 M has a different diff. am I right?

[inTgr8r]

No, The M3 diff is the same unit.

[inTgr8r]

Originally Posted by BTM

If you're asking which ratio to go with, 3.91 and 4.10 are the most popular. I have no personal experience with either, and opinions seem to differ.

re ratios
Here is a spreadsheet that you can plug values into.

The ratio that you select should depend on what you have as goals for where & how you drive the car.

e.g.
If at your favourite track a 4.10 forces you to make another up-shift before the end of the straight, then the 3.91 might be a better choice.

[epbrown]

Originally Posted by IronZ4M

to rebuild my diff. for sure will be cheaper for me but I'm just worry if I bought the ring & pinion and get them to the shop then having a trouble with it after installing it due poor rebuild I just wanna buy a new diff and swap it in.

For a new diff. builded already how much roughly it costs? what is the Ratio difference between 3.91 and 4.10?

Buying a pre-built diff with be over $3000 USD PLUS you'll have to give them your known quantity, probably low-mile diff for something that could have come from a 2001 E46 M3 - that always bugged me, as I had about 5,000 miles when I did mine.

As for the ratios: the 3.91 is 8% over stock, the 4.10 is 13%. Typically people go with the 4.10 unless they have plans for forced induction down the line, in which case popular opinion says go with the 3.91 to avoid traction issues.

I went with the 3.91, as this seemed to be about the limit for most production sports cars outside of Ferrari. Porsche was using 3.88 in the Cayman S that year, BMW went to 3.85 with the E90 M3 soon after - estimates are that it puts 0-60 at 4.5sec or so with the PS2s I added when I went to CSLs, which is quick enough for me. Most people are unimpressed with the difference, though.

[mfanatic325]

Originally Posted by epbrown

Most people are unimpressed with the difference, though.

Yeah, like I said, it depends on overall pricing. Not to say that I'm not happy with the upgrade. Don't get me wrong, I love it.
In fact, I had Scott (iPhoneEngineer) test-drive my car, and even compared to his ESS VT2-500, he had plenty fun with my car. He was quite pleasantly surprised with the pulling power it had, even though I don't have force induction just yet

But I wouldn't say I'd do it all over again, unless I get everything at the same price that I paid, or lower

Just for reference, I bought my 3.91 ring & pinion set ever so slightly used, for $500 shipped, REM polished and everything. Then the labor was around $1k for the rebuild.
I wouldn't pay much more than $1500 for the rebuilt option.

Not sure how much a full diff costs, but as others have said, approximately $3k. Ouch.

[IronZ4M]

Originally Posted by epbrown

Buying a pre-built diff with be over $3000 USD PLUS you'll have to give them your known quantity, probably low-mile diff for something that could have come from a 2001 E46 M3 - that always bugged me, as I had about 5,000 miles when I did mine.

As for the ratios: the 3.91 is 8% over stock, the 4.10 is 13%. Typically people go with the 4.10 unless they have plans for forced induction down the line, in which case popular opinion says go with the 3.91 to avoid traction issues.

I went with the 3.91, as this seemed to be about the limit for most production sports cars outside of Ferrari. Porsche was using 3.88 in the Cayman S that year, BMW went to 3.85 with the E90 M3 soon after - estimates are that it puts 0-60 at 4.5sec or so with the PS2s I added when I went to CSLs, which is quick enough for me. Most people are unimpressed with the difference, though.

Originally Posted by mfanatic325

Yeah, like I said, it depends on overall pricing. Not to say that I'm not happy with the upgrade. Don't get me wrong, I love it.
In fact, I had Scott (iPhoneEngineer) test-drive my car, and even compared to his ESS VT2-500, he had plenty fun with my car. He was quite pleasantly surprised with the pulling power it had, even though I don't have force induction just yet

But I wouldn't say I'd do it all over again, unless I get everything at the same price that I paid, or lower

Just for reference, I bought my 3.91 ring & pinion set ever so slightly used, for $500 shipped, REM polished and everything. Then the labor was around $1k for the rebuild.
I wouldn't pay much more than $1500 for the rebuilt option.

Not sure how much a full diff costs, but as others have said, approximately $3k. Ouch.

I emailed diffsonline yesterday and they send me the price of upgraded diff to 3.91 with stock clutches which the same as what we have originally in our cars and they give me a price of $2395 with the exchange which mean will take mine for that upgraded one and I have to pay plus a refundable $600 core deposit.

I just said Ouch would be that much difference to pay that much? Actually I'm going with forced injection G-Power supercharger and thought it would be fun to upgrade the diff. but would it worth to upgrade for that price?

[mfanatic325]

Originally Posted by IronZ4M

I emailed diffsonline yesterday and they send me the price of upgraded diff to 3.91 with stock clutches which the same as what we have originally in our cars and they give me a price of $2395 with the exchange which mean will take mine for that upgraded one and I have to pay plus a refundable $600 core deposit.

I just said Ouch would be that much difference to pay that much? Actually I'm going with forced injection G-Power supercharger and thought it would be fun to upgrade the diff. but would it worth to upgrade for that price?

Considering that fact that we don't know the overall usage/mileage of the diffs that these companies offer to you (while also knowing that your own diff which you are essentially giving to them is probably low-mileage and pristine), I would feel kind of irked.
Also, like I said, I personally wouldn't spend much more than $1500 TOTAL for a mod like this. EVEN IF it were...say 4.5 final drive ratio

Plus, you're going supercharged. I say go with that first, with the stock diff, and see how you like it. If you can learn to drive with DSC off all the time even with a supercharger, then I say you're ready for diff upgrade

[Starscream]

I have 4.10's in my M and I love them,

Very noticeable difference

[inTgr8r]

Originally Posted by mfanatic325

Considering that fact that we don't know the overall usage/mileage of the diffs that these companies offer to you (while also knowing that your own diff which you are essentially giving to them is probably low-mileage and pristine), I would feel kind of irked.
Also, like I said, I personally wouldn't spend much more than $1500 TOTAL for a mod like this. ..............)

This what has held me back as well.
I would definitely go the route of having mine rebuilt IF I could find someone that I have confidence/trust in to do it.
I know a couple of good indys but I'm not sure if I would trust the job to someone that doesn't specialize in this type of thing.

[mfanatic325]

Originally Posted by inTgr8r

I know a couple of good indys but I'm not sure if I would trust the job to someone that doesn't specialize in this type of thing.

Yeah, the indy I took the the car to for diff rebuild already had plenty of experience with these diffs, so expertise wasn't as big an issue for me as overall pricing was