How to determine gear ratio? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

gregbr · 04-14-2005, 07:59 PM

Hi do you determine the axle gear ratios? Do I count the teeth to get a ratio. It's the 67 4wd with 33's, so it probably is not stock. Thanks.

**JIMs70GMC** · 04-14-2005, 08:19 PM

rotate one tire twice and count the numer of times the driveshaft turns, a little more than 4 would be 4.10s, 4 and half would be 4.56s, etc. if it has a locker than you'd only need to rotate once and have both tires of the ground.

Or remove the rear cover and count the teeth and divide ring gear by pinion for ratio.

70 shorty · 04-14-2005, 08:35 PM

The only way to be exact is to count the teeth. Jim's way is a lot easier though.

Longhorn Man · 04-14-2005, 09:52 PM

Count the teeth...the oil needs chainged anyways.

gregbr · 04-14-2005, 09:57 PM

Thanks!!

cableguy0 · 04-14-2005, 10:21 PM

i agree count the teeth gear oil is overdue for a change

shifty · 04-14-2005, 10:26 PM

LOL. This question gets asked at least once or twice a week

Maybe someone should make it a sticky post.

Someone else said you can take the numbers off of something on the ass-end and figure it out from there, I just ... forgot where the post was.

gregbr · 04-14-2005, 11:32 PM

Only if it's still stock.

04-14-2005, 07:59 PM	#1
gregbr Senoir Member Join Date: Mar 2002 Location: Rock Hill, SC USA Posts: 1,214	How to determine gear ratio? Hi do you determine the axle gear ratios? Do I count the teeth to get a ratio. It's the 67 4wd with 33's, so it probably is not stock. Thanks. __________________ 67 Chevy, Small back glass, Factory 4WD, Factory Shortbed, Factory V8, Lifted 4" 70 GMC Sierra Grande, Factory Shortbed, Factory 402/400 turbo, Super Custom Interior. Numbers matching with SPID & Build Sheet. 68K Original Miles. Restored 2010 70 GMC Restoration Pictures http://67-72chevytrucks.com/gallery/...00&ppuser=4424

04-14-2005, 08:19 PM	#2
JIMs70GMC user # 2756 Join Date: Jun 2001 Location: Chesapeake, Virginia Posts: 4,612	rotate one tire twice and count the numer of times the driveshaft turns, a little more than 4 would be 4.10s, 4 and half would be 4.56s, etc. if it has a locker than you'd only need to rotate once and have both tires of the ground. Or remove the rear cover and count the teeth and divide ring gear by pinion for ratio. __________________ 1970 K25, 8' stepside bed 350/465/205 44 up front, 60 in the rear 4.10s rolling on 33" Dunlop MTs 1986 K5, 350/465/208 Dana 60/14 bolt from a cucv 36" Super Swampers TSL/SX 1983 K20 w/ CUCV axles, 350/700R4/208 sitting on 37" Goodyears 1986 M1031 6.2 diesel, TH400/NP205 locker in the rear and a LS in the front, all stock for now..... 1986 K30, 350/400/205 dana 60 and 14 bolt. I kept the drivetrain. Body/bad and chassis are gone. 1981 K30, 350/465/205 dana 60 and dually 14 bolt. Has a G80, and a flat bed. Going to replace the flat bed. 1985 K20, 350/400/208 10 bolt and SF 14 bolt. I wonder where I can find some 1 tons. Hmmmmm

04-14-2005, 08:35 PM	#3
70 shorty Where's my beer? Join Date: Oct 2004 Location: Glen Allen, VA Posts: 1,772	The only way to be exact is to count the teeth. Jim's way is a lot easier though. __________________ 70 C10, shortstep, .30 over 250,Hurst shifted 3 spd parts hauler. Holley 390, Clifford Intake, Header, ported cylinder head, unknown bigger cam. 79 Corvette L82, 4 spd, black, red interior, headers, flowmasters, and unkown bigger cam. '03 Grand Cherokee Laredo, 4.0 4x4 daily driver. 165K miles, and runs great '08 Tahoe LTZ 4x4 155K

04-14-2005, 09:57 PM	#5
gregbr Senoir Member Join Date: Mar 2002 Location: Rock Hill, SC USA Posts: 1,214	Thanks!! __________________ 67 Chevy, Small back glass, Factory 4WD, Factory Shortbed, Factory V8, Lifted 4" 70 GMC Sierra Grande, Factory Shortbed, Factory 402/400 turbo, Super Custom Interior. Numbers matching with SPID & Build Sheet. 68K Original Miles. Restored 2010 70 GMC Restoration Pictures http://67-72chevytrucks.com/gallery/...00&ppuser=4424

04-14-2005, 10:21 PM	#6
cableguy0 Senior Member Join Date: Apr 2000 Location: Delta,Pa Posts: 14,950	i agree count the teeth gear oil is overdue for a change __________________ Owner of North Point Car Care in Dundalk Md. We specialize in custom exhaust on both modern and classic vehicles. We are a full service auto shop from classics to modern vehicles. Feel free to contact me with questions. I will give a 10% discount to any board member.

04-14-2005, 09:52 PM	#4
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,693	Count the teeth...the oil needs chainged anyways.

04-14-2005, 10:26 PM	#7
shifty Questionable Join Date: Mar 2005 Location: Atlanta Posts: 13,376	LOL. This question gets asked at least once or twice a week Maybe someone should make it a sticky post. Someone else said you can take the numbers off of something on the ass-end and figure it out from there, I just ... forgot where the post was. __________________ If I've got anything up for grabs, it'll be here: 7-hole gauge cluster for a 67-72 p/u FREE (link) I can't check the forum daily. If I don't reply to you within 24 hours, drop me a PM! I'm (hopefully) still alive and will reply faster to a PM.

04-14-2005, 11:32 PM	#8
gregbr Senoir Member Join Date: Mar 2002 Location: Rock Hill, SC USA Posts: 1,214	Only if it's still stock. __________________ 67 Chevy, Small back glass, Factory 4WD, Factory Shortbed, Factory V8, Lifted 4" 70 GMC Sierra Grande, Factory Shortbed, Factory 402/400 turbo, Super Custom Interior. Numbers matching with SPID & Build Sheet. 68K Original Miles. Restored 2010 70 GMC Restoration Pictures http://67-72chevytrucks.com/gallery/...00&ppuser=4424



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