Just put 3.64 in my '97 840ci and HOLY CRAP

[Corellian Corve]

This is probably the single most noticeable mod I've done on any car.

I did a lengthy post comparing my '94 850ci and my '97 840ci and in the end, I felt they were about the same around town, with a nod to the 840, but in sport mode the 850 was a much faster car.

Well, no longer. I finally got around to installing a set of 3.64 gears from dragon850 and now it's not even close. The 840 is an absolute beast - while not as fast as my e39 M5, it sure feels like it would keep up. I know that sounds like a bunch of BS, but I can tell you that gear change completely transformed the car. From a stoplight, in Sport mode, I have to be careful because if I hit the throttle the car leaps off the light.

If anyone has an 840 they feel is a little slower then they would like, DO THIS SWAP.

I've done a lot of gear swaps, a lot of chips in my time, but nothing is as night-and-day as this has been. I'm in love with my 840 all over again.

[mikae31]

Can you say what is the difference in acceleration at 0-62 mile/h ?

[Dash01]

What donor BMW cars can the 3.64 diff be taken from?

[TedBobo]

What donor BMW cars can the 3.64 diff be taken from?

Early 850's with the 4spd auto transmission.

[Wuffer]

Have 3 or 4 3.64 open diffs here - straight bolt in as they came from early 850s Drive up from Anacortes and pick one up!
wuffer at shaw dot ca

[wmealer]

I also have a 3.64 open diff from an early 850. Shoot me a PM if interested.

[dancerst]

I have 3.64 Limited Slip Differential for sale.

[dragon850]

Hehehehe how did this turn into a "for sale" thread?

[llcarlos]

My car seems pretty fast off the line. It's an M73 press car so maybe they put in a 3.15 diff. Probably not. It runs at 110 kph which the computer says is 103 kph at 2000 rpm. It has the correct size tires.

It would be nice to lose 50 kilos up front as it doesn't like quick downhill cloverleaf exchanges.

[72tpik5]

I changed the 3.15 LSD that came in my 97 850 for a 3.64 LSD. Definitely worth the effort.

[Mikekugel]

You are all baaad boys! The rear differential gear change to 3.64 turns an 840CI into a Very fun car! I helped a buddy swap the differential from my 93 850CI into his 94 840CI, and he just Loves it. One thing to be aware of is that there are different differential input yokes. We had to swap his onto mine, and that takes an air impact, and a bit of skill. Is it worth it? Absolutely! What did I put into my 850CI which has the 4 speed auto you might wonder. A Jim Blanton built 4.10 BMW Motorsport gear limited slip! Yes, I do like it, 3000 RPM at 80 MPH, hits 120 MPH very quickly. Enjoy the 8^ madne$$.

[mikae31]

You are all baaad boys! The rear differential gear change to 3.64 turns an 840CI into a Very fun car! I helped a buddy swap the differential from my 93 850CI into his 94 840CI, and he just Loves it. One thing to be aware of is that there are different differential input yokes. We had to swap his onto mine, and that takes an air impact, and a bit of skill. Is it worth it? Absolutely! What did I put into my 850CI which has the 4 speed auto you might wonder. A Jim Blanton built 4.10 BMW Motorsport gear limited slip! Yes, I do like it, 3000 RPM at 80 MPH, hits 120 MPH very quickly. Enjoy the 8^ madne$$.

How quickly?

I think that 3000rpm is a bit too much, since eight will always be a slow car now matter what.

[Mikekugel]

To each their own, but 3000 RPM at 80 MPH is just fine by me. Most USA speed limits at best are 80 MPH. My car is DINAN chipped which raises the torque peak to about 3400 RPM. When I punch it to pass the transmission drops out of overdrive into 3rd gear, and that raises the RPM to around 3400, and the car moves very quickly, with 100 MPH in about 4-5 seconds, and 120 in about 10 seconds total. It is a heavy car, but it can still move very quickly with the right rear gear ratio. The trade off is lower fuel economy on the highway. The all around performance increase most likely makes a differential swap the best bang for your money. Search for all the guys who have done the 3.91 ratio swap.
As an aside, before I decided to swap the differential, I installed Euro M-Sport springs all around, removing the Eibach Pro kit, I have EDC, now it handles very well, and I love the balance. I also installed CSI sway bars, and replaced every rubber bushing from front to rear, and sub frame to body.
My Infiniti G37s coupe is a much more fun car to push very hard, but it isn't a classic car! I have driven Tesla Model S P85d, and owned several other fast cars. I prefer to go to the race track for fun.

[Corellian Corve]

To backup Mikekugel.

First, if you're a high-speed driver, then maybe this isn't your mod. If you care about fuel economy, this isn't your mod.

Also, fast is relative. There isn't a BMW of this era that can compete with a damn FOCUS ST these days. So yeah, they are all slow, sure.

However, I'd argue this shaves .5 or more off the 0-6 times which certainly makes it quick. And the improvement is dramatic over stock.

So for me, where this is a causal driver - mostly around-town with short highway trips, this has made the car EXPONENTIALLY more fun to drive, quicker off the stoplight, and feels a lot closer to my e39 M5 and my e38 740i m-sport then previously, where it was by far the slowest of my V8 BMW's.

Just ordered a GPS G-tech so I'm gonna do some 0-60 runs with my cars and see how they compare.

[8eights]

Have your DME and TCM flashed to a Stage 5 if you want to experience the next level of FUN.

[Corellian Corve]

Have your DME and TCM flashed to a Stage 5 if you want to experience the next level of FUN.

Please explain!?

[8eights]

DINAN PERFORMANCE SOFTWARE

1/96-8/98 Engine Software Download D900-447 C $499 5 units
<1>
1/96-8/98 Stg 2 Engine Sftwre Download D903-4472 C $599 5 units
<1>, (1)
9/98-01 Engine Software Download D900-447TU C $499 5 units
<1>
9/98-8/99 Stg 2 Engine Sftwre Download D903-447TU2 C $599 5 units
<1>, (1)
9/99-01 Stg 2 Engine Sftwre Download D903-447TU2 C $599 5 units
<1>, (1)
9/98-8/99 Stg 3 Engine Software D903-447TU3 C $699 5 units
<1>, (3)
9/99-01 Stg 3 Engine Software D903-447TU3 C $699 5 units
<1>, (3)
1/96-8/98 Stg 4 Engine Sftwre Download D903-4474 C $799 5 units
<1>
9/98-01 Stg 4 Engine Sftwre Download D903-447TU4 C $799 5 units
<1>, (11)
9/98-01 Stg 5 Engine Sftwre Download D903-447TU5 C $999 5 units
<1>
1/97-01 Auto. Transmission Download D902-44A5 C $349 5 units

1/97-01 Stage 4/5 Trans.Software D902-44A5-4 C $349 5 units

96-12/96 Auto. Transmission Chip $349 8 units


The prices are cheaper now, These are based on 9 years ago.

[72tpik5]

Are you suggesting that Dinan has these software upgrades available?

[8eights]

Unless they stopped recently, Got a trans and engine flashed in late 15

[72tpik5]

Unless they stopped recently, Got a trans and engine flashed in late 15

Email sent to Dinan.

[alex840]

Dinan is a very different company than they were in 2015.....not better or worst, just a different way of doing business. They are very very corporate now.

[M6FKN]

What was your 3.46 diff out of? Will an e32 3.46 diff fit the 97 840ci auto?

[killian665]

I don’t know why anyone wastes money on Dinan stuff. Maybe if it was a new car and you wanted to keep your warranty but it’s over priced and super conservative otherwise.

[idfotou]

Pardon my ignorance in all this but what cost are ya all taking about? Is this a home-garage DIY project?

[8eights]

Yes! And you can do it without a lift