Any 6MT'ers running 4.10 diff?

[J08M3]

I've read about a bunch of happy owners with DCT and a new Dinan diff. Is there any 6MT guys who've swapped out the rear for the Dinan 4.10 ?

If so how is it? I'm thinking this would be a great upgrade for me with a street driven car that is 85% city 15% highway. I find cruising around town it's hard to high enough in the RPM range without going to fast. I imagine acceleration is greatly improved with this change and helps keep you in a higher RPM range where this engine is really making its power?

I just wish it wasn't so expensive

Any comments from those who have it?

[Manny212]

+1 I would also like to know. This is most likely going to be my next mod but not for a few months if not next spring.

[endofanera7]

I heard Dinan has a demo car, 6MT with 4.10 diff. Maybe those who test drove it can share...

[dcstep]

Originally Posted by J08M3

I've read about a bunch of happy owners with DCT and a new Dinan diff. Is there any 6MT guys who've swapped out the rear for the Dinan 4.10 ?

If so how is it? I'm thinking this would be a great upgrade for me with a street driven car that is 85% city 15% highway. I find cruising around town it's hard to high enough in the RPM range without going to fast. I imagine acceleration is greatly improved with this change and helps keep you in a higher RPM range where this engine is really making its power?

I just wish it wasn't so expensive

Any comments from those who have it?

I love mine. I'm approaching 1,200 miles on it and will have the lube swapped out next week. The torque gain is between 6% and 7% and you feel it immediately. Cruising in stop and go traffic is actually easier because you stay in second so long as you're moving. I only shift to 1st if I stop.

The real fun is the flexibility in 3d and 4th, where it really squirts. Of course, you gain in 6th gear also.

I bought mine mainly because I plan to autocross and think that the 2d and 3d gear flexibility will be very useful.

There's a slight gear whine on the overrun, but it's low in volume and not annoying to me. You can hear it, but only when coasting. I'm curious to see if the permanent fluid changes it at all. Of course your gas mileage will fall exactly the percentage of the FD ration change.

If you can afford the gas and the install cost, then I'd highly recommend it.

BTW, buy through a BMW dealer and ask for a discount. Also, look to see if Dinan is running a rebate offer also. I got just under 40% discount, when combined with the Dinan rebate. The dealer makes out like a bandit on the install, but they're likely deal on the unit cost. Dinan will charge you full list price if you order it yourself. I found that BMW dealer purchase and install was cheaper than I could have done it with an independent installer.

Dave

[MTrizzy]

thanks for the information... I just started looking into this and will probably order within a week or two.... fyi DINAN is 15% off this month... and I met Steve Dinan at atspeedmotorsports last night...according to him this is the best bang for the buck for the m3.

http://www.atspeedmotorsports.com/

[dcstep]

I did the throttle bodies and 4.10 at the same time. I'll put it on the dyno next week to see the hp vs. torque gains over my baseline stock readings of 333 whp. One thing you know for sure with the 4.10 is that you'll gain over 6% in rear wheel torque, no if ands or buts.

Dave

[J08M3]

dcstep, thanks for the feedback. Do you find while cruising around town it's easier to stay in the main power band of this car? Do you notice if you're getting into the upper range of RPMs more on acceleration?

Where I live, if I'm not on the highway, by the time I hit 8,000 RPM in second gear I'm already far over the posted speed limit. Sometimes it's hard to get the good hard accelerating power to the ground immediately and by the time it's there I'm already speeding. This would be my main reason for changing out the diff. Top speed is totally unnecessary for me.

[GTM]

You do NOT gain power switching to the shorter gears.
Dyno should be come out at similar power level if you compare on wheel speed vs hp chart.

Think of it as compressing powerband, in car's like M3(w/wide powerband engine) can benefit from shorter final drive.



But I still think M3 has pretty short gearing for V8, esp on 1st gear.
I don't want to have too short 1st gear.

[J08M3]

You don't gain power from the engine. But you do gain torque at the rear wheels. Also it will move the RPM range you are staying in at a certain speed. The point would be without changing your speed you can keep the car in it's optimum RPM range. It should also help acceleration off the line while at the same time decreasing wheel spin.

[J08M3]

I agree with the first gear comment though. I think it's almost too low as it is. I think it would be better to have a higher first gear and a lower diff gear

[MrHarris]

A solution to our insanely long gears.

[dcstep]

Originally Posted by J08M3

dcstep, thanks for the feedback. Do you find while cruising around town it's easier to stay in the main power band of this car? Do you notice if you're getting into the upper range of RPMs more on acceleration?

Where I live, if I'm not on the highway, by the time I hit 8,000 RPM in second gear I'm already far over the posted speed limit. Sometimes it's hard to get the good hard accelerating power to the ground immediately and by the time it's there I'm already speeding. This would be my main reason for changing out the diff. Top speed is totally unnecessary for me.

Well, it's only a little over a 6% change, so you'll only be going 6% slower when you hit 8-grand. The speed limit here in Colorado is 75 and I only redline it a few times per week on the street. I do tend to keep it near 4-grand and it's more responsive in all gear; however, it not going to dratically change which gear your in. It IS easy to keep it on it's power band.

I think you'll find it more satisfactory, BUT I'm worried that you're expecting too much change. You generally will be in the same gears, but the rpm will be nearer the torque peak most of the time.

It helps dead starts and acceleration from rolling starts, but speed dependent. It's NOT going to keep you from speeding at 8000 rpm.

Dave

[J08M3]

Originally Posted by dcstep

You generally will be in the same gears, but the rpm will be nearer the torque peak most of the time.

This is exactly what I'm expecting from it. It's not that big of a change from stock 3.85 to 4.10. So I'm not expecting something drastically different. My feeling is that BMW puts the FD a little bit high from the factory to help with MPG.

Do you feel that first gear is too low now?

[mixja]

Originally Posted by GTM

You do NOT gain power switching to the shorter gears.
Dyno should be come out at similar power level if you compare on wheel speed vs hp chart.

Think of it as compressing powerband, in car's like M3(w/wide powerband engine) can benefit from shorter final drive.



But I still think M3 has pretty short gearing for V8, esp on 1st gear.
I don't want to have too short 1st gear.

The definitive difference is that it increases average power output over time (assuming you do a WOT run through the gears). The increase in average power output is much lower than the increased of in-gear torque.

One issue is that increasing your FD means you will have more frequent gear changes. On the DCT transmission this is not an issue because they are so fast. But on the MT transmission, there will be a penalty especially at higher speeds.

[dcstep]

Originally Posted by J08M3

Do you feel that first gear is too low now?

You only need it if you're not rolling. For non-performance driving, I generally run it up to 5-grand in 1st and then jump to 3d.

I always thought it was kind of short and now it's shorter. I think it's another mpg vs. acceleration tradeoff. It's low to give us a nice jump. Still, in the context of using the whole 8400 rpm, it's not low, but for daily driving it seems that way, unless you don't mind running up to 5-grand, which I don't.

Dave

[J08M3]

Would this mod be suggested over an ECU tune? I'm thinking this will be more noticeable and guaranteed results. I won't have to mess with my ECU or worry about any warranty issues. I'm thinking this is going to be my next mod.... Then if I decide I need more ECU would be second.

[signes]

Originally Posted by dcstep

BTW, buy through a BMW dealer and ask for a discount. Also, look to see if Dinan is running a rebate offer also. I got just under 40% discount, when combined with the Dinan rebate. The dealer makes out like a bandit on the install, but they're likely deal on the unit cost. Dinan will charge you full list price if you order it yourself. I found that BMW dealer purchase and install was cheaper than I could have done it with an independent installer.

Dave

Did you get yours done at Gephardt? Would be interesting to see a side by side comparison if we ever get good enough weather for a ride. (1-2 feet due tomorrow...)

[dcstep]

Originally Posted by signes

Did you get yours done at Gephardt? Would be interesting to see a side by side comparison if we ever get good enough weather for a ride. (1-2 feet due tomorrow...)

Got mine a Co's in Loveland.

I'm afraid that Saturday's AX will be a bust. I'm ready if the weather people are wrong again, but it's not looking good...

I plan to run all the AXs that fit my schedule. Right now the only exclusion is May.

Dave

[signes]

Thanks Dave. Saturday will almost surely be snowed out, shame. Looking forward to hearing your exhaust as well (trying to decide what to get...)

[dcstep]

I'm travelling a lot the next couple of weeks, but we could grab a coffee if you're anywhere near 25 and Belleview. We could make a little run so that you could hear it and feel the acceleration.

I'll probably get my dyno runs done next week also.

Dave

[signes]

Sounds good, appreciate it. I will PM you in a couple weeks. Hope you get the auto-X in this weekend (borrow my snows!)

[dcstep]

Still got my friggin snows on!!!

I can't believe that the guys in Minneapolis and Chicago were taking theirs off a month ago.

Dave