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F25 first gear to f20 gearbox

720 views 4 replies 3 participants last post by  alex new 
#1 ·
Is it possible?
I want a first gear on my f20 to give more mph. Because I will put a 3.94 fd to have more accelaration. But first gear is better to give more mph.
Thanks
 
#3 ·
When i bought my mk3 astra turbo it had a f20 box with a f25 diff set fitted.
My previous mk3 gsi had a normal f20 box and the one with the f25 diff set done more mph in every gear .

F20 with F25 diff set

40 mph in first
80 mph in second
112 mph in third
137 mph in fourth
150 mph in fifth :eek:

Hope this helps
 
#4 ·
Code:
Gearbox    1st   2nd   3rd   4th   5th   6th   rev   FDR
=========================================================
F10/F13    3.55  1.96  1.3   0.89  0.71        3.31  4.18
F15/F17w   3.73  1.96  1.32  0.95  0.76        3.31  4.18
F15/F17c   3.73  2.14  1.41  1.12  0.89        3.31  4.18
F16w       3.55  1.95  1.28  0.89  0.71        3.33  3.94
F16c       3.55  2.16  1.48  1.13  0.89        3.33  3.55
F18w(3.74) 3.58  1.87  1.23  0.92  0.74        3.33  3.74
F18c(3.57) 3.58  2.14  1.48  1.12  0.89        3.33  3.57
F20(3.55)  3.55  2.16  1.48  1.13  0.89        3.33  3.55
F20(3.72)  3.55  2.16  1.48  1.13  0.89        3.33  3.72
F20(W5)    3.55  2.16  1.48  1.13  0.74        3.33  3.55
F23        3.58  2.02  1.35  0.98  0.81        3.31  3.84
F25        3.38  1.76  1.12  0.89  0.77        3.17  3.82
F28        3.57  2.16  1.45  1.1   0.89  0.74  3.32  3.72
F35        3.38  1.76  1.12  0.89  0.71        3.17  4.05
F40w       3.77  2.04  1.32  0.95  0.75  0.62  3.54  3.55
F40c       3.77  2.04  1.36  1.05  0.85  0.71  3.54  3.91

OK it's the Final drive on the F25 that makes 1st lower speed.
 
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