Anyone Converted to 318ti Driveline?

[bmwman91]

Court over at Metric Mechanic was telling me that he highly recommends the conversion to a 318ti driveline (G250 tranny, driveshaft, 3.45 LSD) because the tranny gear ratios are closer. I did a comparison with the G240 that the E30 uses and things didn't seem much closer, although the 318ti setup would gear me ~4% lower overall. It also looks like 3rd gear would pull a bit better.

Anyway...anyone done it? Supposedly it is very straightforward and you just need to swap the E30 output flanges into the E36 diff. I am considering it simply because my tranny is 20+ years old and who knows when it will blow!

[DesktopDave]

Sounds good to me.  I haven't done it myself though.  Opinion seems to be that the G250 is a bit more durable than the G240.

While you're out there looking for Ti parts, I've heard the late 90's 6-cyl Z3 has a real torsen geared diff that you might also want to spend some time looking for.

[NO717]

I will be putting in the g250 once my motor is built myself. Little info I came by in the searches, other than that the lower shifting rod must be shortened. And the e30 drive shaft is shortened from the rear most nut.

Now I am not sure if the diff flange is what shortens the length or the drive shaft. The g250 itself is about 2-3 inches longer than the g240.

If you're swapping tranny, shaft and diff, then I don't think they're any issues.

My swap however is just the tyranny with e30 drive shaft and stock 4.10. Until I can find a damn 3.9 or 3.7 LSD here in Germany. 400-700 euros for a used LSD here.

God I miss somethings back home.

[bmwman91]

Great info, thanks! So, the stock selector rod needs to be shortened...could you just use the one from the 318ti? Cutting & welding the stock one is not a problem for me since I have a MIG welder, but I always prefer to stay OEM if possible!

Dave, I will have to look into that. The Z3 uses an E30 rear subframe, right? If only I had stuff like that laying around so I could test fit things!

[NO717]

Im not sure if using the e36 shifter would levitate the length difference. Since I have a welder i was going to weld it anyways and not bother the search in the BMW parts bin.

I'm sure theres info out there on selector rod lengths. The good thing is the aluminum shifting arm from the e30 is a perfect fit.

Edit:

Yes the Z3 and z3ms have the same subframe as ours, so it does bolt on. I too found one thats close to our prices there. However I believe they have tall gears, 3.15; atleast the one I was looking at. I'd want one in the 3.9-3.6 max area.

In my rebuild, Im sticking with 1.8l but for maximum head flow and rpms. So a short gearing will help me with the lack of torq and power.

[wazzu70]

I am switching to a ZF320 from the 96+ e36s since I am using an M3 flywheel and clutch which needs the bigger bellhousing.

The G240 and G250/ZF320 have a similar spread of gear ratios by %. The advantage is that the e36 trans have a 1:1 5th gear so commonly available diffs are a nice upgrade.

I actually have a spreadsheet that I used to figure out the best trans/diff combo to get what I wanted.

I also have a list of which model Z3 came with what ratio diff (torsen).

I will try and remember to post up the data.


BTW use the e36 linkage and the arm that holds the pivot bearing cup. Basically you can follow the directions from the M50 swap into the e30.

[bmwman91]

Interesting. Ye,s I would love to see your calc cheet!

So the E36 driveline drops in relatively easily? Court over at MM recommended the 318ti setup mainly because it gives sportier gear ratios while actually weighing less than the E30 318iS driveline.

[wazzu70]

Here is the gearing calculator:


the percentages are change of ratios to determine spacing/step size. I did everything in MPH so you can determine what max speed you can have per gear for racing. Also fairly easy to compare to what you currently have.

The Z3 differential list is on my computer at work, so I will get that too.

[wazzu70]

Z3 differential ratios and what cars had them.

3.07: M54 3.0 manual
3.15: M52 2.8 manual, M52tu 2.5 manual, M52tu 2.8 manual, S54
3.23: S52
3.46: M54 2.5 manual, M54 3.0 auto
3.64: M54 2.5 auto
4.10: M52 2.8 auto, M52tu 2.8 auto
4.27: M52tu 2.5 auto 1999

[carnurd]

Interesting. Ye,s I would love to see your calc cheet!

So the E36 driveline drops in relatively easily? Court over at MM recommended the 318ti setup mainly because it gives sportier gear ratios while actually weighing less than the E30 318iS driveline.

Does it actually weigh less total???  If so maybe thats in my swap future.

[wazzu70]

Bumping this thread. I have the Getrag250 installed, and a medium case 188mm differential. The M42 driveline propshaft is about 20mm too long. No problem as I can fabricate my own mounts further back for the CSB. I removed the nut on the rear driveshaft and collapsed it as far as I could. The driveshaft is still too long to fit!

I used a file to clean up the splines and still could not collapse it the little bit further it needed. Going to work at it more before I pony up a few hundred bucks for a shortened/rebuilt driveline.

Anyone have any tips? Is there no restriction in the driveshaft tube that prevents me from collapsing the unit fully? The splined section does not need to be cut shorter or anything right?

Thanks

[bmwman91]

Based on my discussion with Metric Mechanic, you want to use the 318ti driveshaft. At least it sounded that way!

Try removing the big collar nut and rubber thing from the front half. See how far it will push into the rear half that way. Maybe look down the barrel of the rear half and see if there is some obstruction?

[wazzu70]

I looked into some info on the 318ti and it seemed that driveline would not be much better. I am thinking some of the difference comes from the different motor mount arms in the E36. Anyone held them side by side to see if they move the motor back and by which amount?

Anyway, my direction is to just have the E30 driveshaft shortened properly so the CSB is in the right place and all that. I figured that would be what I would recommend to someone else so I should follow my own advice If the shop does not rebuild the shaft and just shortens it the cost is a lot more reasonable.