Gear ratios

[arcdef]

Hey,


I have a Datusn 280z which has a 3UZ engine swap with the auto transmission and i am preparing to convert to a manual. I am having issues deciding what gearbox to use as the ratios on offer dont seem to work (in my mind atleast)

The car currently has a 3.34 diff (but was hoping to put in a 3.54 subaru LSD diff at same time) and is running 16" wheels.

There are various conversion kits on offer for the following boxes and these are a few examples of speed for each one, I guess i am after input on if you think the ratios will work in day to day driving or will i just shift from 2nd to 6th and that be it?

Most are similar close ratio 6speeds, the RX7 box is the most promising but they are much more expensive. Do you think i could like with the close ratio 6 speeds?

Lexus is200 - 70mph in 6th = 3000rpm
1st 29mph
2nd 52mph
3rd 76mph
4th 93mph
5th 113 mph
6th 130 mph


Mazda rx8 - 70mph in 6th = 2900rpm
1st 29mph
2nd 49mph
3rd 67mph
4th 93mph
5th 111 mph
6th 132 mph



BMW 330D - 70mph in 6th = 3000rpm
1st 26mph
2nd 45mph
3rd 69mph
4th 94mph
5th 115 mph
6th 135 mph


RX7 5speed - 70mph in 5th = 2700rpm
1st 33mph
2nd 55mph
3rd 80mph
4th 111mph
5th 140 mph



Thanks for taking the time to read!

 

[Zuffen]

Most 6 speed manuals in V8 powered vehicles have huge overdrives and quite often 5th and 6th are both overdrive ratios.

If I had to make the choice I would go for the BMW box as I think it is man enough to handle the torque. not sure the others would be up to the task long term.

First is a bit low but 3,000rpm at 70 is working the engine quite hard.

My rover is doing 2100rpm at 70 and is below the torque curve so could do with a lower diff ration.

Your change in diff ratio is only about 6% but that is 200rpm at 70.

I'd be inclined to try and stay around 3.34 or even down to 3.0 with the BMW box.