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

**richard2717** · 10-09-2018, 04:55 PM

I seem to recall someone posting that if the Blazer was originally 6cyl that it would have come with a 4:11 rear end to make up for the lack of power. Does anyone know of any truth to that? I have been unsuccessful in my search so far

Thanks
Richard

Mike C · 10-09-2018, 08:27 PM

What are you trying to find out? If you have 4.10 gears? Or if your truck was originally a 6 banger?

2 wheel drive or 4 wheel drive? If you have a 4 wheel drive truck and no one has really messed with it, look for the Dana ratio tag on the front axle. It is under one of the cover bolts. Unless some moron PO took it off and didn't put it back... It will be a number like 10/41 which is 10 teeth on the pinion and 41 on the ring gear. So 41 divided by 10 (I think it is backwards on the tag but don't recall. On some newer ones they stamped the ratio. Or maybe I'm confusing early Jeeps? is 4.10.

**1rippen6** · 10-09-2018, 09:47 PM

So far all the 6 cyl. blazers I had were 3:73s I think a total of 3

**truckster** · 10-09-2018, 10:49 PM

GM Heritage Center says the base engine was the 6 cylinder with a 3.73 rear end ratio. Here's the link:

https://www.gmheritagecenter.com/doc..._Full-Size.pdf

**richard2717** · 10-09-2018, 10:49 PM

I just got curious is all. One of my blazers was originally 6cyl 3ott and I have seen several people mention that they were 411 to make up for weak power. I always thought if there was no mention on the spid then they were usually 308. The blazer is tucked in a back corner so not real accessible at the moment and thought I would pose the question here

Killer Bee · 10-10-2018, 12:04 AM

looks like some good replies above..

don't know much about V6, mine are all V8..

if it helps, dana tags look like these, good luck!

'71 K20 burb D44 4.09 front [4.10 rear]

'72 K1500 burb D44 3.07 front [3.08 rear]
[moron that removed it left in glove box]

but the chrome cover looks ok tagless

'66 GMC truck D60 4.10 rear

**richard2717** · 10-10-2018, 10:15 AM

I gotta move a few things out of the way to see it clearly but I can see there is still the tag on the front of the dana axle. Thanks for all the info

**richard2717** · 10-11-2018, 04:58 PM

well I got one of my guys to pull the tag off of the 6cyl blazer so I could clean it enough to read it. As I was hoping it is 3:73 and the rear has factory posi. After I had him put it back on I decided to get him to pull the tag off the front of my other one that is factory 307 3Ott. To my surprise it is also 3:73 but no posi. My Blue parts blazer was 350/350 and the tag on that one is 3:07 so it makes me wonder if the transmission played more in the rear gear decision than the motor?

.

**1rippen6** · 10-11-2018, 05:02 PM

Possibly, all the 6 cylinder blazers were 3ott.

Mike C · 10-15-2018, 01:14 PM

The motor dictated the gear usually. But sometimes other combos could affect what ratio it came with.

I've only had 350 ci trucks. 3 of them, all '72's. One Blazer 350/TH350, one Jimmy 350/TH350 and one Jimmy 350/SM465 and all had 3.07 gears. I was pretty sure the 6 cylinder trucks were all 3.73 and I think 307 4x4 trucks got 3.73 as well. But those were just the standard ratio. You could option different ratios so you would need to see the SPID on each truck to know if it came with the standard or optional gear.

It's irritating when someone changes the fluid or cover and ditches the ratio tag. Glad to see most haven't! I have an '86 K30 that lists 3.73 on the SPID that someone has lined out and handwritten 4.10. But the front diff tag was still on it showing 3.73. But when I pulled the cover to put a Spartan locker in it it had 4.10s. That is a good example of when they SHOULD have ditched the tag!

HARDCORECASH · 10-15-2018, 05:39 PM

Quote:

Originally Posted by 1rippen6

Possibly, all the 6 cylinder blazers were 3ott.

I thought the same thing. Just looked at a 69 Blazer that has an inline 6 with an automatic. VIN Starts with BKS14 and had Turbo Hydra on the SPID. Guy let me take some pics but did not want to sell.........

**richard2717** · 10-15-2018, 05:42 PM

Quote:

Originally Posted by HARDCORECASH

I thought the same thing. Just looked at a 69 Blazer that has an inline 6 with an automatic. VIN Starts with BKS14 and had Turbo Hydra on the SPID. Guy let me take some pics but did not want to sell.........

Would love to see that spid pic. I have never come across a 6cyl auto in the Blazers

**1rippen6** · 10-15-2018, 06:37 PM

Quote:

Originally Posted by HARDCORECASH

I thought the same thing. Just looked at a 69 Blazer that has an inline 6 with an automatic. VIN Starts with BKS14 and had Turbo Hydra on the SPID. Guy let me take some pics but did not want to sell.........

I meant all the blazers I have bought were 3ott.

HARDCORECASH · 10-15-2018, 10:19 PM

Here you go. The firewall markings say it all. It was cool to stumble upon. Just wish it was for sale. Lol

**richard2717** · 10-16-2018, 06:54 AM

Hardcore
Thanks for the pics. I have seen plenty of 3 speeds one 4 speed but never an auto with the 6cyl. Now I can say I have, lol.

Richard

simicrintz · 10-16-2018, 10:23 AM

Had one of those GE clocks when I was a kid

HARDCORECASH · 10-16-2018, 11:30 AM

Quote:

Originally Posted by richard2717

Hardcore
Thanks for the pics. I have seen plenty of 3 speeds one 4 speed but never an auto with the 6cyl. Now I can say I have, lol.

Richard

I wish I could have looked it over longer. Curious to what gears it had.....

10-09-2018, 04:55 PM	#1
richard2717 Equal opportunity joke ofender Join Date: Oct 2011 Location: Eastern Shore of MD Posts: 10,127	rear end gear ratio question I seem to recall someone posting that if the Blazer was originally 6cyl that it would have come with a 4:11 rear end to make up for the lack of power. Does anyone know of any truth to that? I have been unsuccessful in my search so far Thanks Richard __________________ Members I have met. Dually Jams, OlBlue60, ScottH, Tommyboy24, Dujobo, Warbucket, 2003 Silverado, Notsolo, my90k5, 6t727t2, Special-K ,Jack_71C10, tabarcus,72blazer_mud_bogger,pwdcougar,RSavage,EricSean,1Rippen6,invicta455,tennaragtop71,arks, Kendal,Bennett68C10, Perpendicular, Chainsawman, McGeesCustomMinis,ShortbedClayton,longblue72,6768chevylover,Tim71,Travisarmenta,Ol' Drippy,fleetmitch,georgieb51,Dave,bcnya2,Dadsburb https://paypal.me/6772GMtruckparts Most women like the strong, silent type… Fortunately for me, my wife prefers the out-of-shape, mouthy type.

10-09-2018, 08:27 PM	#2
Mike C Registered User Join Date: Dec 1999 Location: Austin, TX, USA Posts: 7,727	Re: rear end gear ratio question What are you trying to find out? If you have 4.10 gears? Or if your truck was originally a 6 banger? 2 wheel drive or 4 wheel drive? If you have a 4 wheel drive truck and no one has really messed with it, look for the Dana ratio tag on the front axle. It is under one of the cover bolts. Unless some moron PO took it off and didn't put it back... It will be a number like 10/41 which is 10 teeth on the pinion and 41 on the ring gear. So 41 divided by 10 (I think it is backwards on the tag but don't recall. On some newer ones they stamped the ratio. Or maybe I'm confusing early Jeeps? is 4.10. __________________ 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

10-09-2018, 09:47 PM	#3
1rippen6 Senior Member Join Date: May 2011 Location: Greencastle PA Posts: 6,799	Re: rear end gear ratio question So far all the 6 cyl. blazers I had were 3:73s I think a total of 3

10-09-2018, 10:49 PM	#4
truckster Senior Member Join Date: Jan 2001 Location: Orem, Utah Posts: 7,976	Re: rear end gear ratio question GM Heritage Center says the base engine was the 6 cylinder with a 3.73 rear end ratio. Here's the link: https://www.gmheritagecenter.com/doc..._Full-Size.pdf __________________ I have sworn upon the altar of God, eternal hostility against every form of tyranny over the mind of man. - Thomas Jefferson

10-09-2018, 10:49 PM	#5
richard2717 Equal opportunity joke ofender Join Date: Oct 2011 Location: Eastern Shore of MD Posts: 10,127	Re: rear end gear ratio question I just got curious is all. One of my blazers was originally 6cyl 3ott and I have seen several people mention that they were 411 to make up for weak power. I always thought if there was no mention on the spid then they were usually 308. The blazer is tucked in a back corner so not real accessible at the moment and thought I would pose the question here __________________ Members I have met. Dually Jams, OlBlue60, ScottH, Tommyboy24, Dujobo, Warbucket, 2003 Silverado, Notsolo, my90k5, 6t727t2, Special-K ,Jack_71C10, tabarcus,72blazer_mud_bogger,pwdcougar,RSavage,EricSean,1Rippen6,invicta455,tennaragtop71,arks, Kendal,Bennett68C10, Perpendicular, Chainsawman, McGeesCustomMinis,ShortbedClayton,longblue72,6768chevylover,Tim71,Travisarmenta,Ol' Drippy,fleetmitch,georgieb51,Dave,bcnya2,Dadsburb https://paypal.me/6772GMtruckparts Most women like the strong, silent type… Fortunately for me, my wife prefers the out-of-shape, mouthy type.

10-10-2018, 12:04 AM	#6
Killer Bee Registered User Join Date: Jan 2016 Location: Barber City, CA Posts: 4,809	Re: rear end gear ratio question looks like some good replies above.. don't know much about V6, mine are all V8.. if it helps, dana tags look like these, good luck! '71 K20 burb D44 4.09 front [4.10 rear] '72 K1500 burb D44 3.07 front [3.08 rear] [moron that removed it left in glove box] but the chrome cover looks ok tagless '66 GMC truck D60 4.10 rear __________________ *I started out with nothing - and I still have most of it*

10-10-2018, 10:15 AM	#7
richard2717 Equal opportunity joke ofender Join Date: Oct 2011 Location: Eastern Shore of MD Posts: 10,127	Re: rear end gear ratio question I gotta move a few things out of the way to see it clearly but I can see there is still the tag on the front of the dana axle. Thanks for all the info __________________ Members I have met. Dually Jams, OlBlue60, ScottH, Tommyboy24, Dujobo, Warbucket, 2003 Silverado, Notsolo, my90k5, 6t727t2, Special-K ,Jack_71C10, tabarcus,72blazer_mud_bogger,pwdcougar,RSavage,EricSean,1Rippen6,invicta455,tennaragtop71,arks, Kendal,Bennett68C10, Perpendicular, Chainsawman, McGeesCustomMinis,ShortbedClayton,longblue72,6768chevylover,Tim71,Travisarmenta,Ol' Drippy,fleetmitch,georgieb51,Dave,bcnya2,Dadsburb https://paypal.me/6772GMtruckparts Most women like the strong, silent type… Fortunately for me, my wife prefers the out-of-shape, mouthy type.

10-11-2018, 04:58 PM	#8
richard2717 Equal opportunity joke ofender Join Date: Oct 2011 Location: Eastern Shore of MD Posts: 10,127	Re: rear end gear ratio question well I got one of my guys to pull the tag off of the 6cyl blazer so I could clean it enough to read it. As I was hoping it is 3:73 and the rear has factory posi. After I had him put it back on I decided to get him to pull the tag off the front of my other one that is factory 307 3Ott. To my surprise it is also 3:73 but no posi. My Blue parts blazer was 350/350 and the tag on that one is 3:07 so it makes me wonder if the transmission played more in the rear gear decision than the motor? . Attached Images __________________ Members I have met. Dually Jams, OlBlue60, ScottH, Tommyboy24, Dujobo, Warbucket, 2003 Silverado, Notsolo, my90k5, 6t727t2, Special-K ,Jack_71C10, tabarcus,72blazer_mud_bogger,pwdcougar,RSavage,EricSean,1Rippen6,invicta455,tennaragtop71,arks, Kendal,Bennett68C10, Perpendicular, Chainsawman, McGeesCustomMinis,ShortbedClayton,longblue72,6768chevylover,Tim71,Travisarmenta,Ol' Drippy,fleetmitch,georgieb51,Dave,bcnya2,Dadsburb https://paypal.me/6772GMtruckparts Most women like the strong, silent type… Fortunately for me, my wife prefers the out-of-shape, mouthy type.

10-11-2018, 05:02 PM	#9
1rippen6 Senior Member Join Date: May 2011 Location: Greencastle PA Posts: 6,799	Re: rear end gear ratio question Possibly, all the 6 cylinder blazers were 3ott.

10-15-2018, 01:14 PM	#10
Mike C Registered User Join Date: Dec 1999 Location: Austin, TX, USA Posts: 7,727	Re: rear end gear ratio question The motor dictated the gear usually. But sometimes other combos could affect what ratio it came with. I've only had 350 ci trucks. 3 of them, all '72's. One Blazer 350/TH350, one Jimmy 350/TH350 and one Jimmy 350/SM465 and all had 3.07 gears. I was pretty sure the 6 cylinder trucks were all 3.73 and I think 307 4x4 trucks got 3.73 as well. But those were just the standard ratio. You could option different ratios so you would need to see the SPID on each truck to know if it came with the standard or optional gear. It's irritating when someone changes the fluid or cover and ditches the ratio tag. Glad to see most haven't! I have an '86 K30 that lists 3.73 on the SPID that someone has lined out and handwritten 4.10. But the front diff tag was still on it showing 3.73. But when I pulled the cover to put a Spartan locker in it it had 4.10s. That is a good example of when they SHOULD have ditched the tag! __________________ 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

10-15-2018, 10:19 PM	#14
HARDCORECASH Registered User Join Date: Aug 2014 Location: Williston, ND Posts: 287	Re: rear end gear ratio question Here you go. The firewall markings say it all. It was cool to stumble upon. Just wish it was for sale. Lol Attached Images

10-16-2018, 06:54 AM	#15
richard2717 Equal opportunity joke ofender Join Date: Oct 2011 Location: Eastern Shore of MD Posts: 10,127	Re: rear end gear ratio question Hardcore Thanks for the pics. I have seen plenty of 3 speeds one 4 speed but never an auto with the 6cyl. Now I can say I have, lol. Richard __________________ Members I have met. Dually Jams, OlBlue60, ScottH, Tommyboy24, Dujobo, Warbucket, 2003 Silverado, Notsolo, my90k5, 6t727t2, Special-K ,Jack_71C10, tabarcus,72blazer_mud_bogger,pwdcougar,RSavage,EricSean,1Rippen6,invicta455,tennaragtop71,arks, Kendal,Bennett68C10, Perpendicular, Chainsawman, McGeesCustomMinis,ShortbedClayton,longblue72,6768chevylover,Tim71,Travisarmenta,Ol' Drippy,fleetmitch,georgieb51,Dave,bcnya2,Dadsburb https://paypal.me/6772GMtruckparts Most women like the strong, silent type… Fortunately for me, my wife prefers the out-of-shape, mouthy type.

10-16-2018, 10:23 AM	#16
simicrintz Registered User Join Date: Dec 2017 Location: Escondido Posts: 305	Re: rear end gear ratio question Had one of those GE clocks when I was a kid __________________ -Bruce 1971 K5 Blazer 4WD



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