What gearbox+diff combo would produce this....

[wakdog]

So I just took a M50 swapped 325i for a test drive and was a little stumped as to what gearbox/diff setup the car is running...

5th gear 110kmh (68mph) and its sitting on 3500rpm.......

Diff back case says S3.73 but the owner has told me it has a 3.91 ratio in it....

As far as I can see the only way this can be right is if the car has a 3.91 diff and a 1:1 5th gear which is stupidly close for something I would want to daily drive (my race car has an M20 with G260 + 4.1 LSD and i find that way to high revving to drive on the motorway...)

[nrubenstein]

All E3) transmissions had a 1:1 5th.

[DTM190]

All E3) transmissions had a 1:1 5th.

In whos dreams?

[DTM190]

What RPM does your race car sit at doing 110? I have a calculator in excel somewhere, will dig it up

[wakdog]

Cant really remember the racecar rpm, its been off the road having 2.7L stroker built since early this year but im guessing about 3300rpm ish

[DTM190]

Have a play with calc http://www.csgnetwork.com/rpmcalc.html

Sounds lie 4.27 if it had the non existant 0.81 5th box

Or 3.46 if it did have a 1:1 5th box

[wakdog]

68mph
25inch tire (car is running 205/55/16 tires)
3.73:1 Final drive
1:1 5th

= 3408rpm

68mph
25inch tire (car is running 205/55/16 tires)
3.91:1 Final drive
1:1 5th

= 3573rpm


hmmm so maybe the guy is wrong and it does have a 3.73 diff, cause its definitely closer to 3400rpm @ 110 than it is 3600....

Wonder how hard it would be to get a 3.25:1 LSD in AUS or if someone would wan to swap one for this 3.73....

::: The M50 car feels similar to my racecar when it had a 4.45:1 (that was fun... welded 4.45 hehehe)

[DTM190]

I worked on tyre size close to factory.
Reason being BMW would use the original tyre size to calibrate the speedo.
The larger OD tyres are only going to change actual speed, not alter the speedo to rpm equation unless you were using a GPS to measure speed?

[dreamchasin]

I run NVm50>G260>4.10 LSD and I love it :D

[Wanganstyle]

All 5 speed manual gearboxes Paired OEM by BMW to 24v engines had 1:1 5th gear; basically the 4th of any e30 original 5 speed transmission.

3.47, 3.38, 3.25, 3.23, 3.15, 3.07, 2.93 are all popular ratios to run with a 1:1 non-overdrive 5th gear in an e30 with 24v swap



***


3.73+ 1:1 5th gear 5mt is pretty insane, not a daily driver option if fuel costs are of concern.

6 speed manual with 3.73 is good though, e46M3 with getrag 6mt has a 3.62 final drive standard.

[dreamchasin]

I don't get bad gas mileage with my setup I have above. Not the greatest and I beat on my e30. Maybe Luke 18-20.

[Wanganstyle]

non vanos M50 was paired OEM by BMW with a 4.10 in some e34's. its not terrible as the NV lacks torque on bottom end to pull the 3800lb sled around; this was great for my e34it.

[lbreevesii]

big calculator/comparison tool here:

http://gafiero.org/speedcalc.shtml

[wakdog]

I ended up buying the car, got it on the hoist and it is a 3.91 crown/pinion, so im going to just swap it out for a 3.15 I pulled from a scrap eta

[DTM190]

What gearbox does it have, that was the missing link lol.

Pics? Where in aus?