jasonlitka  Apr 3 2006 - 10:33am   

The following equations and rules apply only to 4-cycle engines powered by pump gasoline. The equations have been simplified for ease of understanding. Answers will approximate, but generally close enough for use as a guideline.

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It is recommended that you round your result to the nearest hundreth, ie. 4.118325 = 4.12

Gear Ratio= Rear Axle ratio multiplied by Transmission gear ratio. (Tranny list below) Ex: 4.11*1=4.11 (rear axle=4.11) (1=1:1, fourth gear in some trannies.)

Tire Radius= Distance, in inches, from the center of the tire to the ground.

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MPH
Tire Radius	RPM	Rear End Ratio	Transmission Gear Ratio	=MPH

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RPM
Rear End Ratio	Transmission Gear Ratio	MPH	Tire Radius	=RPM

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Calculated Gear Ratio (Trans. gear multiplied by rear end gear)
Tire Radius	RPM	MPH	=Gear Ratio

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Transmission Gear (relative to variables of calculated gear ratio equation)
Calculated Gear Ratio	Rear end ratio	=Transmission gear ratio

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Rear end gear (relative to variables of calculated gear ratio equation)
Calculated gear ratio	Transmission gear	=Rear end gear

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Tire Radius
MPH	Rear End Ratio	Transmission Gear Ratio	RPM	=Tire Radius

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Transmission	Engine code	1st	2nd	3rd	4th	5th
1982 TH-200C	All	2.74	1.57	1.00
1982 4-sp Muncie	LQ8/LQ9	3.50	2.48	1.66	1.00
	LC1	3.60	2.48	1.66	1.00
	LG4	3.42	2.28	1.45	1.00
	LU5	2.88	1.91	1.33	1.00
1983 TH-200C	LQ8/LQ9	2.74	1.57	1.00
	LC1	2.74	1.57	1.00
1983 TH-700R4	All	3.06	1.63	1.00	.70
1983 4-sp Muncie	LQ8/LQ9	3.50	2.48	1.66	1.00
1983 5-sp Warner Gear	LQ8/LQ9	3.50	2.14	1.36	1.00	.73
	LC1	3.50	2.14	1.36	1.00	.73
	LG4	2.95	1.94	1.34	1.00	.73
1984 TH-700R4	LQ9	3.06	1.63	1.00	.70
	LC1	3.06	1.63	1.00	.70
	LG4	3.06	1.63	1.00	.70
	L69-HO	3.06	1.63	1.00	.70
1984 4-sp Muncie	LQ9	3.50	2.48	1.66	1.00
1984 5-sp Warner Gear	LQ9	3.76	2.18	1.42	1.00	.72
	LC1	3.50	2.14	1.39	1.00	.78
	LG4	2.95	1.94	1.34	1.00	.73
	L69-HO	2.95	1.94	1.34	1.00	.73
1985 TH-700R4	ALL	3.06	1.63	1.00	.70
1985 5-sp Warner Gear	LQ9	3.76	2.18	1.42	1.00	.72
	LB8	4.03	2.37	1.50	1.00	.76
	LG4	2.95	1.94	1.34	1.00	.63
	L69-HO	2.95	1.94	1.34	1.00	.63
1986 TH-700R4	ALL	3.06	1.63	1.00	.70
1986 5-sp Warner Gear	LQ9	3.76	2.18	1.42	1.00	.86
	LB8	3.50	2.14	1.36	1.00	.78
	LG4	2.95	1.94	1.34	1.00	.63
	LG4	3.35	1.93	1.29	1.00	.63
	L69-HO	2.95	1.94	1.34	1.00	.63
	L69-HO	3.35	1.93	1.29	1.00	.61
1987 TH-700R4	ALL	3.06	1.63	1.00	.70
1987 5-sp Warner Gear	LB8	4.03	2.37	1.50	1.00	.76
	LG4	2.95	1.94	1.34	1.00	.63
	LB9	2.95	1.94	1.34	1.00	.63
	LB9	2.95	1.94	1.34	1.00	.73
1988 TH-700R4	ALL	3.06	1.63	1.00	.70
1988 5-sp Warner Gear	LB8	4.03	2.37	1.50	1.00	.76
	LO3	2.95	1.94	1.34	1.00	.63
	LB9	2.95	1.94	1.34	1.00	.73
1989-1992 Not available yet, but here are a couple that are belived to be correct.
1992 T5		2.68	1.80	1.31	1.00	.75
1991 T5	LO3	2.95	1.94	1.34	1.00	.63
T5	TPI Induction	2.75	1.94	1.34	1.00	.74
4L60-E		3.06	1.62	1.00	.70