I have a race prepped 325 that I ran last year in the Kumho Championship. When I bought it I was told it had a 325 Sport box. 3 of my close competitors however run with an M3 box with the bell housing conversion. I am trying to work out the merits of a conversion by looking at the ratios and calculating change up revs, final speeds etc. The piece of the jigsaw I am missing however is the ratios for the Sport box.
I believe that the 325 normal box has an over driven 5th in the following ratios:
3.83 / 2.20 / 1.40 / 1.00 / 0.81
I read somewhere that the Sport box had a different set of ratios from 1st to 3rd:
3.35 / 2.03 / 1.36 / 1.00 / 0.81
However, I read somewhere else that the Sport box was in fact a direct drive 5th with close ratio gears:
3.76 / 2.33 / 1.61 / 1.23 / 1.00
Now I'm just confused. Can anyone sort this me out?
Thanks in advance. James
P.S. I'm pretty sure that the M3 dogleg box has the following:
3.72 / 2.40 / 1.77 / 1.26 / 1.00
Gearbox Ratios - 325 Sport
Moderator: martauto
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Widge
- E30 Zone Addict
- Posts: 3661
- Joined: Tue Jan 11, 2005 11:00 pm
- Location: Leeds
Sport Box
3.35/2.03/1.36/1.00/0.81
325 Box
3.38/2.20/1.40/1.00/0.81
320 box, which is what I'm putting in my touring (325)
3.27/2.02/1.32/1.00/0.81
Don't know what the M3 is, need one of the M3 guys to look in their owners manual.
3.35/2.03/1.36/1.00/0.81
325 Box
3.38/2.20/1.40/1.00/0.81
320 box, which is what I'm putting in my touring (325)
3.27/2.02/1.32/1.00/0.81
Don't know what the M3 is, need one of the M3 guys to look in their owners manual.
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pistonbroke
- E30 Zone Newbie
- Posts: 25
- Joined: Mon Jan 17, 2005 11:00 pm
Widge - I think you may find that 1st on the 320i 'box is 3.72, and 1st on the std. 325i 'box is 3.83
The M3 ratios are 3.72, 2.4, 1.77, 1.26 & 1.00 and is preferable for the circuit as 1st is back and down on the dog leg, meaning 4th & 5th are on the same plane....
The 325i Sport box is closest of the lot but not so good as 5th is out and up on the dog leg, it has the highest 1st at 3.35, hence the final drive drop to 3.9:1
And for more confusion, the 323i dog leg 1st had 3.76, 2.33, 1.61, 1.23 & 1.00 and used a 3.25:1 FD and this is the second 'Sport' box Jimmy P refers to.
If changing to a direct top box you'll need to change the FD up to 3.25 or thereabouts, otherwise you'll have the top end of 4th in the overdrive 5th boxes. Both the 320 & 323i (incl. Sport) boxes aren't as strong as the 325/ M3 boxes.
The M3 ratios are 3.72, 2.4, 1.77, 1.26 & 1.00 and is preferable for the circuit as 1st is back and down on the dog leg, meaning 4th & 5th are on the same plane....
The 325i Sport box is closest of the lot but not so good as 5th is out and up on the dog leg, it has the highest 1st at 3.35, hence the final drive drop to 3.9:1
And for more confusion, the 323i dog leg 1st had 3.76, 2.33, 1.61, 1.23 & 1.00 and used a 3.25:1 FD and this is the second 'Sport' box Jimmy P refers to.
If changing to a direct top box you'll need to change the FD up to 3.25 or thereabouts, otherwise you'll have the top end of 4th in the overdrive 5th boxes. Both the 320 & 323i (incl. Sport) boxes aren't as strong as the 325/ M3 boxes.