Dinan 3.45 DCT rear

[jimmy ny]

I am looking for feedback from owners.....gas mileage, acceleration, rpm differences at speed, etc. Does the car feel that much faster?

[klammer]

I have the 3.45 and have had it for pretty much the life of the car, 25k miles and almost 30 track days in about a year and a half. No issues and have to say I love it! The quicker in gear acceleration comes in real handy in city driving as does the xtra torque I don't really notice the higher highway rpms, which is why I picked the 3.45 over the 3.62. Car definitely feels quicker and a bit more responsive which I really like on the track, as to whether it's "faster", well that's still open to debate and there are many threads about it. Overall, am happy with it and would do it again.

[BMWJ]

rear diff changes are nice. def can get more torque at the road. Also depending how you drive, you can manipulate the RPM band you are in so you can take more advantage of the cars power band.

I will stay OEM though with this car as I don't want to give up any MPG for highway cruising. I don't hit the track

[Ateam]

Really depends on the track as well. If there is a consistent track you use than you should really consider the needs of that track and which gear you typically are in and how often you are in and out of that gear. A lot of tracks you can stay in 2nd gear tons of the time and hit 3rd gear quite often as well. If you change the diff to dinan than you shorten the time you spend in each gear and you end up having to shift more often. Just as a rough example, lets say on this track 1-

Track 1-you spend 75 percent of the time between 55-68mph (which is the upper end of 2nd stock). If you changed to dinan you would only be able to hit say 60mph before having to switch to 3rd and unless you used 3rd for long periods of time, you basically eliminate all that extra torque benefit from being in a lower gear (which way outweighs the benefit of a slightly shorter diff).

Now if a track you spend more time in the 45-55 mph range which is the bottom end of 2nd gear, than the diff would signifigantly help you because you would have more torque at that range in 2nd gear than the OEM 2nd gear due to shorter diff. And since you do not need to hit over 60 in 2nd very often, it does not really matter that you are running out of gear too early.

SO it all depends on the track IMO.

For street driving it is kind of the same. If you like playing around at the top end of the RPM band for fun, then it really depends on what speeds you tend to do that. If you have no qualms about going 120 often than a rear diff will not matter a whole lot either way.

But if you like to really redline the car in the 50-70mph range which is pretty common since that keeps you legal and is freeway speed, than a shorter diff will be bad in the sense that you will be out of 2nd gear by 60 mph instead of 68 and have to shift to third. So burning onto a freeway instead of accelerating all the way to speed, you would have to shift an extra time into the slower third gear instead of bein able to ride the top end of the power curve to the free way speed.

At lower city speeds the diff is helpful because you are not redlining the car and the diff gives you more torque in the bottom end of the rev band (it gives more at all rpm's but since you are spending time near the bottom moreso in city driving the fact you run out of gear quicker doesnt matter)

Thats the stuff I would consider

[jimmy ny]

thanks for all the feedback guys, but i don't really track, I'm just looking for drag race accelatrion

[Ateam]

For a drag it is probably worse since you shift more times and limit your time in 1st and 2nd which are your big torque multiplier gears. For you I do not think you would benefit

[klammer]

Originally Posted by Ateam

For a drag it is probably worse since you shift more times and limit your time in 1st and 2nd which are your big torque multiplier gears. For you I do not think you would benefit

Have to agree, was a big discussion on this and how the stock, 3.45, and 3.62 affect acceleration times in various situations, and most often the stock wins.... The best use is as aforementioned in lower RPM city driving and gearing does only work for the right track, that being said the DCT does take away the negatives (shift speed compensating for the need to shift more frequently) to a certain extent, and really appreciate the "eagerness" of the car now. It's an expensive mod but I love it and it fits me and my car perfectly... Do a search, there's spreadsheets and all sorts of good info on this, it helped me with my decision. Good luck

[enricob]

Originally Posted by klammer

I have the 3.45 and have had it for pretty much the life of the car, 25k miles and almost 30 track days in about a year and a half. No issues and have to say I love it! The quicker in gear acceleration comes in real handy in city driving as does the xtra torque I don't really notice the higher highway rpms, which is why I picked the 3.45 over the 3.62. Car definitely feels quicker and a bit more responsive which I really like on the track, as to whether it's "faster", well that's still open to debate and there are many threads about it. Overall, am happy with it and would do it again.

do you remap DCT software?

I've installed a 3.62 some months ago, for track use I think is a good upgrade (sometimes gears are too short). But I have problems with software, DCT didn't work well

[Ateam]

This mod is neither good nor bad. It truly depends on how you use your car. Kind of like a manual v. Dct Some situations a manual is better and some situations the dct is better or more desirable.

Sounds like the OP though would not really benefit for the cost this would be.

I heard you also have to raise limiter to 8600 rpms-is that true for the dct?

[klammer]

I did nothing to the DCT and you don't have to raise any limiters, especially the 3.45. As enricobob mentioned, have heard issues with the 3.62, but have not heard nor experienced any problems with the 3.45 and DCT. Limiter raising, I believe, is done to counteract the problem of losing speed due to having to shift earlier, but not necessary. It works great on my home track and love it on the city, but as stated, not cheap and is fairly idiosynchratic in its application. But love it

[flipm3]

Originally Posted by Ateam

Really depends on the track as well. If there is a consistent track you use than you should really consider the needs of that track and which gear you typically are in and how often you are in and out of that gear. A lot of tracks you can stay in 2nd gear tons of the time and hit 3rd gear quite often as well. If you change the diff to dinan than you shorten the time you spend in each gear and you end up having to shift more often. Just as a rough example, lets say on this track 1-

Track 1-you spend 75 percent of the time between 55-68mph (which is the upper end of 2nd stock). If you changed to dinan you would only be able to hit say 60mph before having to switch to 3rd and unless you used 3rd for long periods of time, you basically eliminate all that extra torque benefit from being in a lower gear (which way outweighs the benefit of a slightly shorter diff).

Now if a track you spend more time in the 45-55 mph range which is the bottom end of 2nd gear, than the diff would signifigantly help you because you would have more torque at that range in 2nd gear than the OEM 2nd gear due to shorter diff. And since you do not need to hit over 60 in 2nd very often, it does not really matter that you are running out of gear too early.

SO it all depends on the track IMO.

For street driving it is kind of the same. If you like playing around at the top end of the RPM band for fun, then it really depends on what speeds you tend to do that. If you have no qualms about going 120 often than a rear diff will not matter a whole lot either way.

But if you like to really redline the car in the 50-70mph range which is pretty common since that keeps you legal and is freeway speed, than a shorter diff will be bad in the sense that you will be out of 2nd gear by 60 mph instead of 68 and have to shift to third. So burning onto a freeway instead of accelerating all the way to speed, you would have to shift an extra time into the slower third gear instead of bein able to ride the top end of the power curve to the free way speed.

At lower city speeds the diff is helpful because you are not redlining the car and the diff gives you more torque in the bottom end of the rev band (it gives more at all rpm's but since you are spending time near the bottom moreso in city driving the fact you run out of gear quicker doesnt matter)

Thats the stuff I would consider

I agree with everything Ateam mentioned. This is very good advice.

Originally Posted by klammer

I did nothing to the DCT and you don't have to raise any limiters, especially the 3.45. As enricobob mentioned, have heard issues with the 3.62, but have not heard nor experienced any problems with the 3.45 and DCT. Limiter raising, I believe, is done to counteract the problem of losing speed due to having to shift earlier, but not necessary. It works great on my home track and love it on the city, but as stated, not cheap and is fairly idiosynchratic in its application. But love it

So you enjoy the gears at Autobahn CC? I haven't been there in many years, but upon my return back to Illinois, I plan dedicating that as my "home" track. I am debating on what gears to get for the E90 and E46 based off that track.

[klammer]

Love the gears at Autobahn. Funny thing was at first I didn't, kept finding myself in third needing to shift right before the braking zone or else just bounce of the limiter for a second, but after learning the track and carrying more speed, I know find the gearing perfect as I'm now in 4th most of the time. Love the track, love the car, and it's only 45 min door to door from downtown

[flipm3]

Originally Posted by klammer

Love the gears at Autobahn. Funny thing was at first I didn't, kept finding myself in third needing to shift right before the braking zone or else just bounce of the limiter for a second, but after learning the track and carrying more speed, I know find the gearing perfect as I'm now in 4th most of the time. Love the track, love the car, and it's only 45 min door to door from downtown

Thanks for the feedback!! I am so pumped for next years track season and being able to develop driving skill.

By any chance do you have a baller membership there or just go to all the track days you can go to?

[klammer]

All the track days I can go to... Actually there right now!

[Hujan]

Originally Posted by jimmy ny

I am looking for feedback from owners.....gas mileage, acceleration, rpm differences at speed, etc. Does the car feel that much faster?

Thought I would bump this thread as I've been considering the Dinan 3.45 diff for my M3 for awhile now.

My M3 is my daily driver and I do a decent amount of city driving. I get out for 3-4 group rides a year and will be doing at least a few track days a year as well. I do not plan to every S/C the car and have been focusing on reasonable ways to add a little pep to the car's step (exhaust, intake, pulley, tune). My thinking is that a 3.45 diff might enhance what I've already done without radically altering the feel of the car.

Also, at the moment, I have an opportunity to get the whole thing (parts and labor) done for $2300.

I'm curious whether those of you with the diff are still happy with your decision to get it.

[Hujan]

Bump. Need to make a decision on this soon. No one has any thoughts? C'mon diff users, speak up!

[OM VT3]

Originally Posted by Ateam

For a drag it is probably worse since you shift more times and limit your time in 1st and 2nd which are your big torque multiplier gears. For you I do not think you would benefit

Lol it's a dct it's FAR better day and night I've got them and I've got an ess 650 kit! Car pulls very hard!!! 3rd and 4th gear I don't get into 5th to much......only sometimes haha

[Hujan]

Originally Posted by leigh

Lol it's a dct it's FAR better day and night I've got them and I've got an ess 650 kit! Car pulls very hard!!! 3rd and 4th gear I don't get into 5th to much......only sometimes haha

Which came first: ESS 650 or the 3.45 diff?

[OM VT3]

Originally Posted by Hujan

Which came first: ESS 650 or the 3.45 diff?

The ess kit! Car still needs more power.......needs vt3

[Stainless 45]

Don't have any experience to report but after all the research I've done this is definitely going to get done as soon as the funds allow. Nothing beats low-end grunt, which the M3 lacks. I've swapped the gears in other cars and the difference is night and day.

[dparm]

klammer, how much was the install of that new FD?

[Hujan]

Appreciate the comments so far. Seems like the 3.45 is a no brainer.