LSD stock vs 3.45 vs 3.62 for DCT

[doba_s]

I just want to see you people think about changing final drive. Would you leave it stock, go with 3.45, or with 3.62 ?

[doba_s]

[Sticky]

A few threads on the subject already, I'm gong to a 3.62. Don't do a 3.45 and then wonder what you could have had. Don't fear the gear if keeping the car NA, best mod you can do.

[doba_s]

Originally Posted by Sticky

A few threads on the subject already, I'm gong to a 3.62. Don't do a 3.45 and then wonder what you could have had. Don't fear the gear if keeping the car NA, best mod you can do.

thank you for your input ... i couldn't decide which to get ...

I guess 3.62 it is ...

[JuniorM3]

Why less top speed?, lower speed in each gear? extra shift from 0-100km/h?

[camaross305]

Originally Posted by JuniorM3

Why less top speed?, lower speed in each gear? extra shift from 0-100km/h?

Because you get about 10% more RWTQ.... to the ground

[mixja]

If you're going to change it, I'd go with the 3.62, if you do wheel torque vs speed graphs, the 3.62 is better than stock and 3.45.

Put it one way, if you're rolling next to a stock C63 at 30mph in 3rd gear and you both nail it, you'll be pulling ahead all the way until around 82mph where the C63 will have slightly more pull until 89mph and from then on the M3 with 3.62 will pull away once more. In other words, you'll slaughter the C63 because by the time you are at 80mph, you'll have pulled a number of car lengths ahead...

If you compare the above scenario with a DCT running a 3.45 diff, the 3.45 reduces the amount of time the C63 has an advantage from 7mph to 5mph and at a slightly higher speed, but you're running 5% less torque at the wheels so you don't pull away as much (I'd rather have 5% more torque than a measly 2mph less disadvantage)

One thing to bear in mind is if you go 3.45 or 3.62, you're going to have an extra gear change on the quarter mile as 4th gear will run out around 112.4mph on 18-inch wheels on the 3.45 diff (and even lower on the 3.62 diff)...

Another interesting point is that if you go with the 3.62, your fourth gear is basically the same as the stock MT third gear...

[Sticky]

Originally Posted by mixja

If you're going to change it, I'd go with the 3.62, if you do wheel torque vs speed graphs, the 3.62 is better than stock and 3.45.

Put it one way, if you're rolling next to a stock C63 at 30mph in 3rd gear and you both nail it, you'll be pulling ahead all the way until around 82mph where the C63 will have slightly more pull until 89mph and from then on the M3 with 3.62 will pull away once more. In other words, you'll slaughter the C63 because by the time you are at 80mph, you'll have pulled a number of car lengths ahead...

If you compare the above scenario with a DCT running a 3.45 diff, the 3.45 reduces the amount of time the C63 has an advantage from 7mph to 5mph and at a slightly higher speed, but you're running 5% less torque at the wheels so you don't pull away as much (I'd rather have 5% more torque than a measly 2mph less disadvantage)

One thing to bear in mind is if you go 3.45 or 3.62, you're going to have an extra gear change on the quarter mile as 4th gear will run out around 112.4mph on 18-inch wheels on the 3.45 diff (and even lower on the 3.62 diff)...

Another interesting point is that if you go with the 3.62, your fourth gear is basically the same as the stock MT third gear...

I think the extra gear change does not really matter with DCT. The changes take .004 of a second according to BMW. I think DCT is going to make the gear change a moot point, all the benefit, no downside (other than MPG and top speed).

Very interested point the 4th gear DCT and 3rd gear manual.

[noxredna]

I am assuming that 3.62 is under development right now? are they being released by dinan or other companies? any updates on them? Definitely an interesting mod..

[Sticky]

Originally Posted by noxredna

I am assuming that 3.62 is under development right now? are they being released by dinan or other companies? any updates on them? Definitely an interesting mod..

3.62's are out... from Diffsonline and Dinan has to update their site but they should have them as well.

[doba_s]

Originally Posted by mixja

If you're going to change it, I'd go with the 3.62, if you do wheel torque vs speed graphs, the 3.62 is better than stock and 3.45.

Put it one way, if you're rolling next to a stock C63 at 30mph in 3rd gear and you both nail it, you'll be pulling ahead all the way until around 82mph where the C63 will have slightly more pull until 89mph and from then on the M3 with 3.62 will pull away once more. In other words, you'll slaughter the C63 because by the time you are at 80mph, you'll have pulled a number of car lengths ahead...

If you compare the above scenario with a DCT running a 3.45 diff, the 3.45 reduces the amount of time the C63 has an advantage from 7mph to 5mph and at a slightly higher speed, but you're running 5% less torque at the wheels so you don't pull away as much (I'd rather have 5% more torque than a measly 2mph less disadvantage)

One thing to bear in mind is if you go 3.45 or 3.62, you're going to have an extra gear change on the quarter mile as 4th gear will run out around 112.4mph on 18-inch wheels on the 3.45 diff (and even lower on the 3.62 diff)...

Another interesting point is that if you go with the 3.62, your fourth gear is basically the same as the stock MT third gear...

good review ...

[doba_s]

Originally Posted by noxredna

I am assuming that 3.62 is under development right now? are they being released by dinan or other companies? any updates on them? Definitely an interesting mod..

I am scheduling appointment with Dinan to do 3.62 next week ... we will see how is their schedule looking on monday

[e46e92love]

Does anyone does the analysis and would be willing to list side by side the difference in speed in each gear and overall top speed between the 3.62 and stock? I have no clue how to do that....

[Sticky]

Originally Posted by e46e92love

Does anyone does the analysis and would be willing to list side by side the difference in speed in each gear and overall top speed between the 3.62 and stock? I have no clue how to do that....

It has already been done, you could try searching: http://www.m3post.com/forums/showpos...0&postcount=36

[doba_s]

Sticky are you getting 3.62 as well ?

[Sticky]

Originally Posted by doba_s

Sticky are you getting 3.62 as well ?

Yes.

[M3 996]

Anyone know what 80 mph "cruising" RPM would look like with the 3.62? Currently, a 80 mph clip happens ~3000 RPM.

[JMD0977]

Just so you guys know, my 3.62 is running perfectly and shifts in D mode perfectly as well. Im in Cali right now testing my car.

This is very important though, BMW made 2 different diff covers for the M3. One for the Mt(bigger) and one for the DCT(smaller). Why? , I dont know. BMW has 2 different part numbers for the diff cover DCT and MT. I had a problem where the stock DCT diff cover did not work with the 3.62 and I needed a MT diff cover to go on my diff cuz the DCT cover was to small. I dont have enough time to explain but you guys get the idea. Nobody knows this since they had never tested the DCT 3.62.
I'll post the full details later. Worst case, you'll need to order a MT diff cover from BMW ($430).

[Sticky]

Originally Posted by JMD0977

Just so you guys know, my 3.62 is running perfectly and shifts in D mode perfectly as well. Im in Cali right now testing my car.

This is very important though, BMW made 2 different diff covers for the M3. One for the Mt(bigger) and one for the DCT(smaller). Why? , I dont know. BMW has 2 different part numbers for the diff cover DCT and MT. I had a problem where the stock DCT diff cover did not work with the 3.62 and I needed a MT diff cover to go on my diff cuz the DCT cover was to small. I dont have enough time to explain but you guys get the idea. Nobody knows this since they had never tested the DCT 3.62.
I'll post the full details later. Worst case, you'll need to order a MT diff cover from BMW ($430).

If you could PM me the details I would appreciate it as my car is going under the knife as we speak.

I would also like to hear your impressions, the car should feel really "alive" now.

[Sticky]

Originally Posted by M3 996

Anyone know what 80 mph "cruising" RPM would look like with the 3.62? Currently, a 80 mph clip happens ~3000 RPM.

If you just clicked the link 3 posts above you, you would have all the information you need.

[e46e92love]

Originally Posted by M3 996

Anyone know what 80 mph "cruising" RPM would look like with the 3.62? Currently, a 80 mph clip happens ~3000 RPM.

Looks like it pops up to 3700 or so. No thanks.

[Sticky]

Originally Posted by e46e92love

Looks like it pops up to 3700 or so. No thanks.

Well, how would you put the gears in without the car first?