Diff Ratio

[BMWTouring 20]

Hi guys, what would be the correct diff ratio for a M52 320i been converted to manual?? Cheers.

[leithcm 0]

Hi guys, what would be the correct diff ratio for a M52 320i been converted to manual?? Cheers.

Depends on the auto you had before. If it was a JATCO, their top gear is 0.7:1 ratio (over drive), so check the diff you have now - it might be 3.64 - or 3.94:1 - not sure. However, this info is on the diff housing. Multiply this by 0.7 and that will give a new ratio (2.64 or so). As the manual gearboxes are 1:1 in top gear this new diff ratio will give the same engine revs in top at a given speed as before. You want to cruise at higher speeds with lower engine revs? Go one step lower in the diff. pretty sure this is how it works, but could be wrong........... Cheers.

[westy 614]

Something between a 3-3.25/1

[*Glenn* 854]

I'm running a 3.15:1 in mine. 2,800rpm in 5th @ 100kph. Calculated top speed of 245kph in 5th. I'm more than happy with the ratio. With the bigger engine I could have gone to a 2.97:1 for slightly better economy.....depends what you want.

What manual gearbox did you fit ??

Edited August 6, 2009 by *Glenn*

[BMWTouring 20]

I'm running a 3.15:1 in mine. 2,800rpm in 5th @ 100kph. Calculated top speed of 245kph in 5th. I'm more than happy with the ratio. With the bigger engine I could have gone to a 2.97:1 for slightly better economy.....depends what you want.

What manual gearbox did you fit ??

I havent converted it just yet, just want to get all the bits together.

Must check what diff ratio is in there at the moment as I'd rather do the job all at once and do it properly.