Gear Ratio Calculator

# of Drive Teeth: Axle Ratio:
Tire Diameter:
# of Driven Teeth:

Drive gears

All GM

# of teethGear colorGM part #Shaft sizeClip size
8 Black 6261783 1.19" 5/16
10 Purple 6261785 1.19" 5/16
18 Green 6260037 1.19" 7/16
19 Natural 8640188 1.19" 7/16
15 Grey 8642620 1.19" 5/16
17 Red 8640517 1.19" 5/16

Small driven gears

Power glide, 200 Metric, TH250, TH350 and TH400

# of teethGear colorGM part #
18Brown3987918
19Natural3987919
20Blue3987920
21Red3987921
22Grey3987922
23Black3980346

Small driven gears

200R-4 and 125 Metric

# of teethGear colorGM part #
26Brown25502669
27Black410731
28Yellow416765
29Green403999
30Blue561035
31White403417

Large driven gears

200 Metric, TH250, TH350, TH400 and 700R-4

# of teethGear colorGM part #
34Green9774413
35Orange9780387
36Natural1359270
37Red1359271
38Blue1359272
39Brown1359273
40Black1362048
25513047
41Yellow1362195
42Green1362049
25513049
43Purple1362196
25513050
44Grey9780470
45Lt. Blue9775187


Speedo gear chart for the 700R/4L60/4L60E

15-Tooth Drive Gear

Gear RatioTire SizeDriven Gear
4.563342
4.563539
4.102645
4.102745
4.102844
4.102943
4.10 30 41
4.10 31 40
4.10 33 38
4.10 35 35
3.73 26 43
3.73 27 42
3.73 27 1/2 41
3.73 28 40
3.73 29 39
3.73 30 38
3.7331 36


17-Tooth Drive Gear

Gear RatioTire SizeDriven Gear
3.73 28 45
3.73 29 44
3.42 26 45
3.42 26 1/2 44
3.42 27 43
3.42 28 42


18-Tooth Drive Gear

Gear RatioTire SizeDriven Gear
3.23 26 45
3.23 26 1/2 44
3.23 27 43
3.23 28 42