Gears ? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

yellow70 · 01-30-2011, 03:09 PM

Hi, new to game of rebuilding a Blazer. How do i find out what gears are in the front of my 71 blazer without opening it? The guy i bought from said the rear had been changed. Thanks

Mike C · 01-30-2011, 07:44 PM

Unless some previous owner took it off and tossed it, there should be a metal tag on the front diff underneath two of the cover bolts showing what the front ratio is. Usually it is covered in grease, so spray around the cover with carb cleaner and a brush. If it is missing, this would be a good opportunity to change the fluid in the front. Was the rear rebuilt or was the ratio changed? Either way, I would want to know for sure. I have a K30 with a Dana 60 front that the tag is gone off of. The front driveshaft was out when I got the truck, and someone has drawn a line through the 3.73 on the SPID and written in 4.10. All of these things are red flags to me, so both covers are going to have to come off to figure out exactly what some PO has jacked with.

Critter · 01-31-2011, 12:44 AM

Quote:

Originally Posted by Mike C

...All of these things are red flags to me, so both covers are going to have to come off to figure out exactly what some PO has jacked with.

I agree. Just pull the cover and count the teeth, it's the best way to be 100% sure. Besides, I'm sure that axle could use some fresh gear oil anyway.

Blazer1970 · 01-31-2011, 07:38 AM

If it came with a 350, it came with 3.07 gears. If it came with a 6 cyl. or a 307, it came with 3.73 gears. Any other ratio would be listed on the SPID.

NW_Ryker · 01-31-2011, 10:04 PM

My blazer with a 350 came with 3.73 gears. If he changed the gearing in the back and not the front he would've blown his t-case right?

yellow70 · 01-31-2011, 11:44 PM

My blazer with a 350 came with 3.73 gears. If he changed the gearing in the back and not the front he would've blown his t-case right? I hope not!!

yellow70 · 01-31-2011, 11:47 PM

If it came with a 350, it came with 3.07 gears. If it came with a 6 cyl. or a 307, it came with 3.73 gears. Any other ratio would be listed on the SPID.
__________________
Tim Thanks!

01-30-2011, 03:09 PM	#1
yellow70 Registered User Join Date: Mar 2006 Location: Heber Springs Arkansas Posts: 117	Gears ? Hi, new to game of rebuilding a Blazer. How do i find out what gears are in the front of my 71 blazer without opening it? The guy i bought from said the rear had been changed. Thanks

01-30-2011, 07:44 PM	#2
Mike C Registered User Join Date: Dec 1999 Location: Austin, TX, USA Posts: 7,727	Re: Gears ? Unless some previous owner took it off and tossed it, there should be a metal tag on the front diff underneath two of the cover bolts showing what the front ratio is. Usually it is covered in grease, so spray around the cover with carb cleaner and a brush. If it is missing, this would be a good opportunity to change the fluid in the front. Was the rear rebuilt or was the ratio changed? Either way, I would want to know for sure. I have a K30 with a Dana 60 front that the tag is gone off of. The front driveshaft was out when I got the truck, and someone has drawn a line through the 3.73 on the SPID and written in 4.10. All of these things are red flags to me, so both covers are going to have to come off to figure out exactly what some PO has jacked with. __________________ 44 Willys MB 52 M38A1 64 Corvette Coupe 68 Camaro 'vert LT1 & TH700 69 Z/28 355 12.6's @110 69 Chevy Short Step 4 1/2"/7" drop 72 Jimmy 4WD 4spd 4" & 35's 02 GMC 2500HD 4x4 Duramax

01-31-2011, 07:38 AM	#4
Blazer1970 Registered User Join Date: Dec 1999 Location: Old Mission, MI, USA Posts: 2,507	Re: Gears ? If it came with a 350, it came with 3.07 gears. If it came with a 6 cyl. or a 307, it came with 3.73 gears. Any other ratio would be listed on the SPID. __________________ Tim

01-31-2011, 10:04 PM	#5
NW_Ryker Registered User Join Date: Jul 2010 Location: Carnation Wa Posts: 199	Re: Gears ? My blazer with a 350 came with 3.73 gears. If he changed the gearing in the back and not the front he would've blown his t-case right?

01-31-2011, 11:44 PM	#6
yellow70 Registered User Join Date: Mar 2006 Location: Heber Springs Arkansas Posts: 117	Re: Gears ? My blazer with a 350 came with 3.73 gears. If he changed the gearing in the back and not the front he would've blown his t-case right? I hope not!!

01-31-2011, 11:47 PM	#7
yellow70 Registered User Join Date: Mar 2006 Location: Heber Springs Arkansas Posts: 117	Re: Gears ? If it came with a 350, it came with 3.07 gears. If it came with a 6 cyl. or a 307, it came with 3.73 gears. Any other ratio would be listed on the SPID. __________________ Tim Thanks!



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