VW Gear Ratios (originally from the EM Sport webpage, visit them at EM Sport
Codes located at bottom of Bell Housing
Tranny Code

FO  (11/78-5/79)
FN,FF,FH  (to 7/80)
FN,FF,FH,FJ  (from '81)
4Y,9A,ACD,AEN (8v Close Ratio)
4S
7D,7A
IS
FK,FM,FD  (Close Ratio)
2H  (83 GTI Close Ratio)
4K
ACH  ('85 1.6 Diesel)
ASF,AON,ACN,ACL  (8v)
AOP,AGS  (86-90 1.6 Diesel)
AGB,2Y  (16v Close Ratio)
AUG  (1.8 8v)
AWY  ('90 Diesel)
AMC,CHE  (from '93 115hp)
ATH
APW
AVX
ACL
APW,CHB  (from '93 1.8)
VW Motorsport 8V
VW Motorsport 16V
GP  (3+E from '81)
GY  (3+E PU)
GC  (to '80)
GC  (from '81)
final
drive
3.89
3.89
3.89
3.67
3.94
3.94
3.94
3.89
3.94
3.94
3.94
3.67
3.94
3.67
3.67
3.94
3.67
3.67
3.67
4.25
3.67
3.67
????
????
4.17
3.89
3.89
3.89
1st
 
3.45
3.45
3.45
3.45
3.45
3.45
3.45
3.45
3.45
3.45
3.45
3.45
3.45
3.45
3.45
3.45
3.45
3.45
3.45
3.45
3.45
3.45
2.50
2.72
3.45
3.45
3.45
3.45
2nd

1.94
1.94
1.94
2.12
1.94
1.94
1.94
2.12
2.12
2.12
1.94
1.97
1.94
2.12
1.94
1.94
1.94
1.94
1.75
1.94
1.94
1.94
1.79
2.06
1.75
1.75
1.94
1.94
3rd

1.29
1.29
1.29
1.44
1.29
1.29
1.29
1.44
1.44
1.44
1.44
1.37
1.37
1.44
1.44
1.44
1.29
1.29
1.37
1.29
1.37
1.37
1.42
1.68
1.06
1.06
1.29
1.29
4th

.97
.97
.91
1.13
.91
.91
.91
1.13
1.13
1.13
.91
1.03
1.03
1.13
1.13
1.13
.97
.91
.97
.91
1.03
.97
1.17
1.43
.71
.71
.97
.91
5th

.76
.76
.71
.89
.75
.71
.75
.91
.91
.89
.75
.75
.75
.91
.89
.89
.80
.75
.85
.75
.75
.85
1.03
1.26
 
 
 
 
RPM/Speed calculator   
Tire size:  
width (mm)  
sidewall ratio   
rim size (in)  

Final Drive:   
Gear ratio:   
Option 1: 
RPM   

Option 2: 
speed   
kph or mph?   
  

example:

for 
195-50-15 
tires

width = 195
sidewall = 50
rim = 15

fd = 3.89
gear = .89

RPM = 3600
gives: 
speed = 112kph, 
       70 mph

speed = 140
kph/mph = kph
gives: 
RPM = 4464rpm
     

VW MotorSport Ring & Pinions (small input shaft, 8v): 4.20, 4.46, 4.64, 4.81, 5.07
VW MotorSport Ring & Pinions (large input shaft, 16v): 3.32, 4.20, 4.46, 4.64, 4.81, 5.07

Via Drew MacPherson (on the scirocco mailing list):

    Here's a chart of transmission code and axle flanges (A2 transmissions) from the VW parts catalogue. There may be some aaplications missing, butI tried to cover most of them. I did not specify gas vs diesel, but I think as a ROT most gas transmissions in Dijifant applications (ie 100hp and up) are 100mm flanges, while most CIS and Diesel applications (85-90 hp) are 90mm flanges. The obvious exception to this that I've found are of course 85+ Sciroccos and Cabs, and some early A2 Jetta GLs. YMMV.

90 mm flange
Code     (Application)
++++    ++++++++++++
ACN     (07/84-09/86 GOLF)
             (08/84-07/85 JETTA)
ACH     (07/84-09/86 GOLF)
             (08/84-07/85 JETTA)
AGS     (08/86-07/87 GOLF)
             (08/86-07/87 GOLF)
AOP     (08/88-07/89 GOLF)
             (10/87-07/88 JETTA)
AEN    (11/87-07/88 JETTA)
ASF      (09/87-05/88 GOLF)
             (09/87-05/88 JETTA)
4S         (08/87-08/88 JETTA)
AWY   (08/89-07/91 GOLF)
             (08/89-07/90 JETTA)
AVX    (01/91-07/92 JETTA)
100 mm flange
Code     (Application)
++++    +++++++++++++
9A         (08/84-07/85 GOLF)
              (01/85-07/85 JETTA)
              (07/84-07/84 RABBIT)
             (07/84-07/84 SCIROCCO)
2Y        (09/87-05/88 GOLF)
             (10/87-05/88 JETTA)
             (07/87-07/88 SCIROCCO)
ACD     (09/87-05/88 GOLF)
             (10/87-10/87 JETTA)
AGB     (09/87-09/87 GOLF)
             (02/87-07/87 JETTA)
             (02/86-07/89 SCIROCCO)
ACL     (08/87-09/87 JETTA)
AON    (09/87-10/87 GOLF)
             (09/87-05/88 JETTA)
AUG    (08/89-07/90 GOLF)
             (08/89-07/90 JETTA)
 


Download a DOS program written by Drew MacPherson that allows you to interactively cycle through transmissions, gears, MPH / KPH and tire sizes. Comes with control files to add new tires, & gears. Fun for the whole family!

Get It! (click to download)