3.0Si Roadster Rear Diff options

[Darryl_1983]

I'm looking to reduce the rear diff ratios on my 3.0 Si Roadster. It is my understanding that the current diff is a 3.23 188K being a manual car.

I bought a 3.46 diff from what I believe was an earlier E85 model, I'm not sure if this is a 188K or 188L.

The first question I have is whether there is going to be an issue fitting a 188L diff into a car which has a 188K diff currently?

Second question, are there any markings on the diff that state which version the diff is? If I like the ratios the plan would be to get a Blackline LSD fitted in the summer, and i noticed there is a different diff listed for earlier models with the 188L to the later models with 188K

And finally, to anyone who has played around with diff ratios, do you think a 3.46 or 3.64 diff is the better overall option for a weekend car that is driven mostly for fun? I originally bought the 3.46 diff as it was available cheap and I figured it'd be a good chance to test for little cost. But I've recently owned a 130i which I believe came with a 3.46 diff. It definitely felt quicker than the Z4, but also on reflection, I don't think a slightly shorter diff would have been too short either.

 

[Z4supercharged]

you can buy e46, (only six sylinder) diff, its almost direct fit. you have to change backplate from your own car orginal diff. I have changed 320i e46 diff 3.38 ratio and bought m-factory lsd. its expensive but good

I think that last letter is only meaning that diff backplate

https://shop.rallybaron.fi/product/185/bmw-188k-mfactory-20-metal-plate-limited-slip-differential-lsd
but be sure you order right one.

 

[Rsipad]

It is my understanding that the current diff is a 3.23 188K being a manual car.

I think the facelift manuals have a 3.46 stock. My 2006 3.0i manual was a 3.46 stock and I thought it was a 3.07 :roll:

I was hoping to go from 3.07->3.64 but ended up going 3.46->3.64. Still very worth it. The drivetrain loss reduction made the car feel like it gained ~25hp. It was almost as substantial to the driving experience as going from 3.0i to 3.0si horsepower via the 3SIM.

The RPM gain during daily driving felt like it was worth the trade off. At around 80 mph indicated, it sat at 3200 RPM.

 

[damocell]

I'm looking to reduce the rear diff ratios on my 3.0 Si Roadster. It is my understanding that the current diff is a 3.23 188K being a manual car.

I bought a 3.46 diff from what I believe was an earlier E85 model, I'm not sure if this is a 188K or 188L.

The first question I have is whether there is going to be an issue fitting a 188L diff into a car which has a 188K diff currently?

Second question, are there any markings on the diff that state which version the diff is? If I like the ratios the plan would be to get a Blackline LSD fitted in the summer, and i noticed there is a different diff listed for earlier models with the 188L to the later models with 188K

And finally, to anyone who has played around with diff ratios, do you think a 3.46 or 3.64 diff is the better overall option for a weekend car that is driven mostly for fun? I originally bought the 3.46 diff as it was available cheap and I figured it'd be a good chance to test for little cost. But I've recently owned a 130i which I believe came with a 3.46 diff. It definitely felt quicker than the Z4, but also on reflection, I don't think a slightly shorter diff would have been too short either.

If you look at the sticker on the diff it'll tell you the ratio, afaik all the 6 cylinder Z4's ran the 188k diff which needs a specific LSD or machining to fit one from a 188. I've just bought an upgraded and rebuilt ZF plated LSD with 6 plates from a e36 and had it fitted to a case with a 3.73 FD. Looking forward to the change from 3.46 that i currently have. Might sell the stock diff, but I'm not sure yet

Untitled by Damien Bower, on Flickr