gear ratio - The 1947 - Present Chevrolet & GMC Truck Message Board Network

WORNBRAKES · 06-19-2002, 06:37 PM

I am in the middle of changing my rear end oil before I drive across the country. I want to figure out the rear end ratio but I need specifics on counting the teeth. This is something I have never done before and my Haynes dos't say much. Could anyone help me with this?
Thanks,
Mario

Super Chevy · 06-19-2002, 06:40 PM

I think you count the teeth on the ring then divide that number by the number of teeth on the pinion

.02

SC

bigvinnie · 06-19-2002, 06:45 PM

yeah, what he said... like if you got 41 ring gear teeth and 11 pinion teeth, 41/11 = 3.727 or 3.73:1 ratio....

WORNBRAKES · 06-19-2002, 06:57 PM

I am having a hard time seeing the pinion. Take a look.

WORNBRAKES · 06-19-2002, 06:58 PM

here is another

bigvinnie · 06-19-2002, 07:08 PM

you should be able to get in there with a good light and see it from the right side.... then you can mark on it with some paint or a blob of grease, jack up one side of the axle, rotate the tire and count the teeth.... no worries

WORNBRAKES · 06-19-2002, 07:40 PM

I counted 41 and 10. 4:10 is what I get. 4:11 posi only right. I am going to put fluid in the truck and then change the fluid in the trailer and figure out those gears.

Longhorn Man · 06-19-2002, 08:05 PM

That would explain why you don't want to keep it at 85 MPH on the freeway.

WWWAAAAAAAAAAAAAAAAA!!!! (engine sounds)

**COBALT** · 06-19-2002, 08:33 PM

Jack the truck up in the back, and throw the transmission in neutral. Take off the emergency brake, and have someone turn the driving wheel (or any wheel if you have a locker).

While the ring and pinion are turning you should be able to see better. Heck you might be able to get in there with a wax pencil (white) and mark a tooth, and then count until you see the mark come around again.

Just some ideas.

WORNBRAKES · 06-20-2002, 01:29 AM

Thanks to all for you help. You guys are great. This was the first time I looked that close at a rear end. Well I managed to get the oil changed and figured out the rear ends in the truck and in the trailer.
Truck-4:10
Trailer-3:73
I hope that I don't find any other reason to look at them. lol I read something on an old thread about spinning the tires and counting axel rotations to figure out the ratio. Does anyone know the details on this?
Thanks,
Mario

WORNBRAKES · 06-20-2002, 02:35 AM

Just went out side and noticed that the rear end is leaking. I guess it dont like new oil. lol On the trailer I noticed that someone had used some type of sylicone to assist in the sealing. Does anyone have any idea of a good sylicone to use?
Thanks.

Ed ke6bnl · 06-20-2002, 03:24 AM

Quote:

Originally posted by WORNBRAKES
Just went out side and noticed that the rear end is leaking. I guess it dont like new oil. lol On the trailer I noticed that someone had used some type of sylicone to assist in the sealing. Does anyone have any idea of a good sylicone to use?
Thanks.

I personally like to use the high tem orange sealer for most applications. It is heavey consistancy and I have had little problem with leaks with poor mating surfaces. Ed ke6bnl

ckhd · 06-20-2002, 10:25 AM

Jack up one tire method:

1) Chock the wheels (cram rocks in front and behind so the thing doesn't roll away)
2) jack up one rear tire (duh?) DON'T FORGET the jackstand. Knowing gear ratios isn't worth killing yourself.
3) mark a spot on the tire
4) mark a spot on the drive shaft
5) put tranny in neutral
6) turn the tire TWO full revolutions while counting how many times the driveshaft spins.
7) how many times the driveshaft spins during the two tire revolutions is your gear ratio.

A touch over three turns = 3.07:1
Three and a half = 3.54:1
Three & 3/4 = 3.73:1
Just under four = 3.90:1
A touch over four = 4.11:1
Four and a half = 4.57:1
etc...

Note: This doesn't work on posi and most lockers.

Longhorn Man · 06-20-2002, 05:12 PM

I don't even use the gasket. pure RTV. Never had a problem yet either.

Kas68c10 · 06-21-2002, 09:45 AM

You can check http://randysringandpinion.com[/URL] and use one of their calculators as a check also. My rear has hi temp orange silicone on it, no problems.

06-19-2002, 06:37 PM	#1
WORNBRAKES Senior Member Join Date: Jul 2001 Location: Hughesville, MD Posts: 1,350	gear ratio I am in the middle of changing my rear end oil before I drive across the country. I want to figure out the rear end ratio but I need specifics on counting the teeth. This is something I have never done before and my Haynes dos't say much. Could anyone help me with this? Thanks, Mario __________________ Mario and Mandy Hughesville, MD 20637 69 C10 305/350 71 K5 Basket case 75 K10 Rescue Parting out 77 MG Midget Parting out 15 6.7L Cummins

06-19-2002, 06:45 PM	#3
bigvinnie Registered User Join Date: Aug 2001 Location: escondido, ca 92026 Posts: 1,222	yeah, what he said... like if you got 41 ring gear teeth and 11 pinion teeth, 41/11 = 3.727 or 3.73:1 ratio.... __________________ '72 short step, 350, 700R4, tilt, ps, pdb, a/c, lowered coils, etc., other work in progress... San Diego, CA 72 Stepside Project

06-19-2002, 06:57 PM	#4
WORNBRAKES Senior Member Join Date: Jul 2001 Location: Hughesville, MD Posts: 1,350	I am having a hard time seeing the pinion. Take a look. Attached Images __________________ Mario and Mandy Hughesville, MD 20637 69 C10 305/350 71 K5 Basket case 75 K10 Rescue Parting out 77 MG Midget Parting out 15 6.7L Cummins

06-19-2002, 06:58 PM	#5
WORNBRAKES Senior Member Join Date: Jul 2001 Location: Hughesville, MD Posts: 1,350	here is another Attached Images __________________ Mario and Mandy Hughesville, MD 20637 69 C10 305/350 71 K5 Basket case 75 K10 Rescue Parting out 77 MG Midget Parting out 15 6.7L Cummins

06-19-2002, 07:08 PM	#6
bigvinnie Registered User Join Date: Aug 2001 Location: escondido, ca 92026 Posts: 1,222	you should be able to get in there with a good light and see it from the right side.... then you can mark on it with some paint or a blob of grease, jack up one side of the axle, rotate the tire and count the teeth.... no worries __________________ '72 short step, 350, 700R4, tilt, ps, pdb, a/c, lowered coils, etc., other work in progress... San Diego, CA 72 Stepside Project

06-19-2002, 06:40 PM	#2
Super Chevy Registered User Join Date: Feb 2001 Location: Ohio Posts: 1,025	I think you count the teeth on the ring then divide that number by the number of teeth on the pinion .02 SC

06-19-2002, 07:40 PM	#7
WORNBRAKES Senior Member Join Date: Jul 2001 Location: Hughesville, MD Posts: 1,350	I counted 41 and 10. 4:10 is what I get. 4:11 posi only right. I am going to put fluid in the truck and then change the fluid in the trailer and figure out those gears. __________________ Mario and Mandy Hughesville, MD 20637 69 C10 305/350 71 K5 Basket case 75 K10 Rescue Parting out 77 MG Midget Parting out 15 6.7L Cummins

06-19-2002, 08:05 PM	#8
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,693	That would explain why you don't want to keep it at 85 MPH on the freeway. WWWAAAAAAAAAAAAAAAAA!!!! (engine sounds)

06-19-2002, 08:33 PM	#9
COBALT Senior Member Join Date: Sep 2001 Location: Seattle, WA, USA Posts: 5,817	Jack the truck up in the back, and throw the transmission in neutral. Take off the emergency brake, and have someone turn the driving wheel (or any wheel if you have a locker). While the ring and pinion are turning you should be able to see better. Heck you might be able to get in there with a wax pencil (white) and mark a tooth, and then count until you see the mark come around again. Just some ideas. __________________ '69 3/4 ton C20 2wd-350ci/TH400 '69 3/4 ton Custom 20 2wd-350ci/4sp Manual '99 2wd 5.7 Chevy Tahoe Seattle, WA.

06-20-2002, 01:29 AM	#10
WORNBRAKES Senior Member Join Date: Jul 2001 Location: Hughesville, MD Posts: 1,350	Thanks to all for you help. You guys are great. This was the first time I looked that close at a rear end. Well I managed to get the oil changed and figured out the rear ends in the truck and in the trailer. Truck-4:10 Trailer-3:73 I hope that I don't find any other reason to look at them. lol I read something on an old thread about spinning the tires and counting axel rotations to figure out the ratio. Does anyone know the details on this? Thanks, Mario __________________ Mario and Mandy Hughesville, MD 20637 69 C10 305/350 71 K5 Basket case 75 K10 Rescue Parting out 77 MG Midget Parting out 15 6.7L Cummins

06-20-2002, 02:35 AM	#11
WORNBRAKES Senior Member Join Date: Jul 2001 Location: Hughesville, MD Posts: 1,350	Just went out side and noticed that the rear end is leaking. I guess it dont like new oil. lol On the trailer I noticed that someone had used some type of sylicone to assist in the sealing. Does anyone have any idea of a good sylicone to use? Thanks. __________________ Mario and Mandy Hughesville, MD 20637 69 C10 305/350 71 K5 Basket case 75 K10 Rescue Parting out 77 MG Midget Parting out 15 6.7L Cummins

06-20-2002, 10:25 AM	#13
ckhd Registered User Join Date: Oct 2000 Location: St. Johns, Arizona Posts: 2,660	Jack up one tire method: 1) Chock the wheels (cram rocks in front and behind so the thing doesn't roll away) 2) jack up one rear tire (duh?) DON'T FORGET the jackstand. Knowing gear ratios isn't worth killing yourself. 3) mark a spot on the tire 4) mark a spot on the drive shaft 5) put tranny in neutral 6) turn the tire TWO full revolutions while counting how many times the driveshaft spins. 7) how many times the driveshaft spins during the two tire revolutions is your gear ratio. A touch over three turns = 3.07:1 Three and a half = 3.54:1 Three & 3/4 = 3.73:1 Just under four = 3.90:1 A touch over four = 4.11:1 Four and a half = 4.57:1 etc... Note: This doesn't work on posi and most lockers. __________________ my 2¢ - t.i.o.l.i. Bowen 1968 K20 fleet 1969 K10 swb fleet 1972 K10 Suburban 1972 C10 lwb step 1992 K1500 'burb 1995 K2500 'burb 1997 C1500 'burb 1999 K1500 2000 K1500 'burb Why do I own so many Suburbans?

06-20-2002, 05:12 PM	#14
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,693	I don't even use the gasket. pure RTV. Never had a problem yet either.

06-21-2002, 09:45 AM	#15
Kas68c10 Registered User Join Date: Apr 2000 Location: Freeland,Michigan,USA Posts: 312	You can check http://randysringandpinion.com[/URL] and use one of their calculators as a check also. My rear has hi temp orange silicone on it, no problems. __________________ 1968 SWB Stepside, 250,pwr disc brake and tilt pwr steering, 5 spd tranny, HEI,Accel coil,K&N filter,Seat from a later truck with built in seatbelts, front and rear sway bars, moved gas tank to under the bed, headman hedders, new chrome bumpers,one wire alternator,Weber k550cub carburator...WORK IN PROGRESS, Freeland MI , Just bought a 72 Jimmy!!!!!!!!!!!



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