4 speed transmition gears - The 1947 - Present Chevrolet & GMC Truck Message Board Network

**chev-obsession** · 09-21-2008, 01:26 AM

does anyone know what gears were in the 4-speed manual transmition? also what gears were in 6 cylinder trucks? and what is the top speed capabilities?

PanelDeland · 09-21-2008, 06:47 AM

You can have a couple different rear gears,usually a 3:73 or a 4:11.There are others possible.You can look on the housing and find the code,someone should be able to decode it for you.It may also be on the SPID on the inside of the glovebox.This is assuming no one has changed them.(the truck is 40 years old)I don't know tranny gears but they are pretty low(I don't have my book handy or I would try to look them up).The 6 can be a 292 or a 250 unless it's a GMC V-6.You need to really give more info on the truck for better info.
Top speed is probably about 85-90 but I doubt you want to run it that fast

.One thing to remember is that newer vehicles with OD run lower RPM's than the old trucks because of the OD.You will think it is revving way too high because of this.Tire size can make some difference.
What are you wanting to do? If your goal is hiway cruising you can do some things to help without breaking the budget.Let us know more about the truck and your goals and we can give better suggestions.

Ace in the hole · 09-21-2008, 08:14 AM

if it's the sm465 the gears are:
1st- 6.55 to 1
2nd- 3.58 to 1
3rd- 1.7 to 1
4th- 1 to 1
reverse 6.09 to 1

**chev-obsession** · 09-22-2008, 04:11 PM

ok, i will check the code. do you know were it is located? and no it doesnt say what it is in the glovebox, and the vin number matches so nobody has changed it. i want to put a posi in the truck, but i like the gears that are in it, but i am not sure what i have.

**Yukon Jack** · 09-22-2008, 04:53 PM

Are you wanting to know what rear gear ratio is usually in a truck with a 4 speed or were you asking what gears are in the actual transmission?

If your asking about the rear axle gears, it varies.

A very simple approach to determine your axle's gear ratio is to mark a chalk line on a tire and the driveshaft and then have someone move the vehicle forward slowly as you count how many driveshaft revolutions there are to one tire revolution.

Just over 3 driveshaft revolutions to 1 tire revolution = 3.08 gears
About 3 3/4 revolutions = 3.73 gears
Just over 4 revolutions = 4.10/4.11 gears
Just over 4 1/2 revolutions = 4.56 gears
etc.

Longhorn Man · 09-22-2008, 08:34 PM

and rear gear options/base gear aren't the same for a 1/2 ton and 3/4 ton.
And as far as top end.... all 1/2 tons should be able to hit 100 MPH and still have room to go before hitting the redline, and the same for MOST 3/4 ton trucks.

**chev-obsession** · 09-22-2008, 11:27 PM

ok thanks. this is what i wanted to know.

09-21-2008, 01:26 AM	#1
chev-obsession Senior Member Join Date: Jul 2008 Location: kennewick, WA Posts: 1,513	4 speed transmition gears does anyone know what gears were in the 4-speed manual transmition? also what gears were in 6 cylinder trucks? and what is the top speed capabilities?

09-21-2008, 06:47 AM	#2
PanelDeland I am a Referee of life. Join Date: Jun 2000 Location: Greensboro N.C. Posts: 13,992	Re: 4 speed transmition gears You can have a couple different rear gears,usually a 3:73 or a 4:11.There are others possible.You can look on the housing and find the code,someone should be able to decode it for you.It may also be on the SPID on the inside of the glovebox.This is assuming no one has changed them.(the truck is 40 years old)I don't know tranny gears but they are pretty low(I don't have my book handy or I would try to look them up).The 6 can be a 292 or a 250 unless it's a GMC V-6.You need to really give more info on the truck for better info. Top speed is probably about 85-90 but I doubt you want to run it that fast .One thing to remember is that newer vehicles with OD run lower RPM's than the old trucks because of the OD.You will think it is revving way too high because of this.Tire size can make some difference. What are you wanting to do? If your goal is hiway cruising you can do some things to help without breaking the budget.Let us know more about the truck and your goals and we can give better suggestions. __________________ The 47-present Chevrolet and GMC Truck Message Board Network,it's owners,moderators,members,and associates of any type should not be held responsible for my opinion. You can't fix stupid,not even with duct tape. "My appearance is due to the fact that "GOD" does punish you for having too much fun!" Barrett-Jackson has perfected alchemy,they make rust into gold! "You can lead a horse to water but you can't saddle a duck" "Cleverly disguised as a 'Responsible Adult' "Sometimes your Knight in shining armor is just a retard in tinfoil"

09-21-2008, 08:14 AM	#3
Ace in the hole Registered User Join Date: Apr 2007 Location: Kalamazoo, Michigan, USA Posts: 538	Re: 4 speed transmition gears if it's the sm465 the gears are: 1st- 6.55 to 1 2nd- 3.58 to 1 3rd- 1.7 to 1 4th- 1 to 1 reverse 6.09 to 1 __________________ 1970 K20, 350--- SOLD 05 silverado extended cab short box- duramax Jeep wrangler unlimited

09-22-2008, 04:11 PM	#4
chev-obsession Senior Member Join Date: Jul 2008 Location: kennewick, WA Posts: 1,513	Re: 4 speed transmition gears ok, i will check the code. do you know were it is located? and no it doesnt say what it is in the glovebox, and the vin number matches so nobody has changed it. i want to put a posi in the truck, but i like the gears that are in it, but i am not sure what i have.

09-22-2008, 04:53 PM	#5
Yukon Jack Post Whore Join Date: Feb 2000 Location: Rose Hill, KS, USA Posts: 12,686	Re: 4 speed transmition gears Are you wanting to know what rear gear ratio is usually in a truck with a 4 speed or were you asking what gears are in the actual transmission? If your asking about the rear axle gears, it varies. A very simple approach to determine your axle's gear ratio is to mark a chalk line on a tire and the driveshaft and then have someone move the vehicle forward slowly as you count how many driveshaft revolutions there are to one tire revolution. Just over 3 driveshaft revolutions to 1 tire revolution = 3.08 gears About 3 3/4 revolutions = 3.73 gears Just over 4 revolutions = 4.10/4.11 gears Just over 4 1/2 revolutions = 4.56 gears etc. __________________ 1970 Blazer with a 400 sbc and 4" lift 1980 Pontiac Trans Am, 455 Oldsmobile 2012 Kawasaki Concours 14

09-22-2008, 08:34 PM	#6
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,690	Re: 4 speed transmition gears and rear gear options/base gear aren't the same for a 1/2 ton and 3/4 ton. And as far as top end.... all 1/2 tons should be able to hit 100 MPH and still have room to go before hitting the redline, and the same for MOST 3/4 ton trucks. Last edited by Longhorn Man; 09-22-2008 at 08:35 PM.

09-22-2008, 11:27 PM	#7
chev-obsession Senior Member Join Date: Jul 2008 Location: kennewick, WA Posts: 1,513	Re: 4 speed transmition gears ok thanks. this is what i wanted to know.



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