Ford Bronco Speedo Gearing
To adjust for changing tire size:
http://home.att.net/~jroal/drive.htm
Inputs
Results
http://www3.telus.net/cbradley/speedogearchange.html
Old tire x Old Gear / New Tire = New Gear
OT x OG / NT = NG
Note - Rumor has it that 31" tires usually had a 19 tooth gear, and 235/75/15 tires had a 21 tooth gear
Example:
Old Tire - 29"
Old Gear - 19 tooth
New Tire - 33"
New Gear - ?
235/75/15 = 28.9"
If you change tire size and gears (or just gears), you have to go one step further:
New Gear / Old Ratio x New Ratio = New Gear
Old Tire
Old Gear
New Tire
New Gear
Old Ratio
New Ratio
New Gear
28.9
x 19
= 549.1
/ 33
= 16.639 (17 tooth)
/ 3.55
x 4.56
21.8
29
x 19
= 551
/ 33
= 16.697 (17 tooth)
/ 3.55
x 4.56
21.8
31
x 19
= 589
/ 33
= 17.848 (18 tooth)
/ 3.55
x 4.56
23.1
28.9
x 19
= 549.1
/ 36
= 15.253 (15 tooth)
/ 3.55
x 4.56
19.59
Each tooth on the speedo gear adjusts your speedometer reading by approx. 5%. So when you add a tooth, you reduce the speedometer reading by 5%.
If you figure in the old speedo gear size with the new tire size and then adjust for the gear change size by 113%.
19 tooth x 1.13 = 21.47
Rear Gear Ratio
Factory Axle Code
2:73:1 Ratio
8M
3.08:1 Ratio
YZ
3.27:1 Ratio
5E
3.55:1 Ratio
2K
3.73:1 Ratio
6W
4.10:1 Ratio
N/A
Internal Drive Gears
Part Number
Description
E3ZZ-17285-B
6 Tooth Internal Drive Gear / Black
E3ZZ-17285-A
7 Tooth Internal Drive Gear / Yellow
F0ZZ-17285-A
8 Tooth Internal Drive Gear / Green
Note: The 6 tooth will offer the most combos for numerically higher gear ratios and the greatest degree of accuracy.
Manual Transmissions with 6 Tooth Drive Gear
Not found in OEM applications
Part Number
Description
N/A
3.08 Gear Ratio / Not possible
C0DZ-17271-A
3.27 Gear Ratio / Maroon 16 Speedo Gear
C3DZ-17271-C
3.55 Gear Ratio / White 17 Speedo Gear
C0DD-17271-B
3.73 Gear Ratio / Yellow 18 Speedo Gear
C1DZ-17271-A
4.10 Gear Ratio / Black 20 Speedo Gear
C4OZ-17271-A
4.30 Gear Ratio / Red 21 Speedo Gear
Manual Transmissions with 7 Tooth Drive Gear
1983-1989 T-5 OEM
Pre 1993 T-5 Aftermarket
1996-1998 Cobra T-45 OEM
All Tremec Transmissions
Part Number
Description
C0DZ-17271-A
2.73 Gear Ratio / Maroon 16 Speedo Gear
C0DD-17271-B
3.08 Gear Ratio / Yellow 18 Speedo Gear
C0DZ-17271-B
3.27 Gear Ratio / Pink 19 Speedo Gear
C1DZ-17271-A
3.55 Gear Ratio / Black 20 Speedo Gear
C4OZ-17271-A
3.73 Gear Ratio / Red 21 Speedo Gear
Jeep Part #j3167393
4.10 Gear Ratio / White 23 Speedo Gear
Manual Transmissions with 8 Tooth Drive Gear
1990-1995 T-5 OEM
1996-1998 T-45 OEM Except Cobra
Part Number
Description
C0DD-17271-B
2.73 Gear Ratio / Yellow 18 Speedo Gear
C1DZ-17271-A
3.08 Gear Ratio / Black 20 Speedo Gear
C4OZ-17271-A
3.27 Gear Ratio / Red 21 Speedo Gear
Jeep Part #j3167393
3.55 Gear Ratio / White 23 Speedo Gear
Jeep Part #j3167393
3.73 Gear Ratio / White 23 Speedo Gear
Jeep Part #j3167393
4.10 Gear Ratio / White 23 Speedo Gear
Automatic Transmissions with 7 Tooth Drive Gear
1983-1989 Automatic Transmissions
Part Number
Description
D0AZ-17271-A
2.73 Gear Ratio / Blue 16 Speedo Gear
C7AZ-17271-B
3.08 Gear Ratio / Gray 18 Speedo Gear
C7VY-17271-A
3.27 Gear Ratio / Tan 19 Speedo Gear
C8SZ-17271-B
3.55 Gear Ratio / Orange 20 Speedo Gear
D0OZ-17271-B
3.73 Gear Ratio / Purple 21 Speedo Gear
Jeep Part #j3167393
4.10 Gear Ratio / White 23 Speedo Gear
Automatic Transmissions with 8 Tooth Drive Gear
1990-1998 Automatic Transmissions
Part Number
Description
C7AZ-17271-B
2.73 Gear Ratio / Gray 18 Speedo Gear
C8SZ-17271-B
3.08 Gear Ratio / Orange 20 Speedo Gear
D0OZ-17271-B
3.27 Gear Ratio / Purple 21 Speedo Gear
Jeep Part #j3167393
3.55 Gear Ratio / White 23 Speedo Gear
Jeep Part #j3167393
3.73 Gear Ratio / White 23 Speedo Gear
Jeep Part #j3167393
4.10 Gear Ratio / White 23 Speedo Gear
Please feel free to link to this site so that others can find it. It's easy to link to this site, just copy one of the texts below onto your web page:
Copyright © 2000-2014