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Old 10-09-2018, 04:55 PM   #1
richard2717
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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

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Old 10-09-2018, 08:27 PM   #2
Mike C
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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.
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Old 10-09-2018, 09:47 PM   #3
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Re: rear end gear ratio question

So far all the 6 cyl. blazers I had were 3:73s I think a total of 3
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Old 10-09-2018, 10:49 PM   #4
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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
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Old 10-09-2018, 10:49 PM   #5
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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
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Old 10-10-2018, 12:04 AM   #6
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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
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Old 10-10-2018, 10:15 AM   #7
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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
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Old 10-11-2018, 04:58 PM   #8
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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?

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Old 10-11-2018, 05:02 PM   #9
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Re: rear end gear ratio question

Possibly, all the 6 cylinder blazers were 3ott.
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Old 10-15-2018, 01:14 PM   #10
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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!
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Old 10-15-2018, 05:39 PM   #11
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Re: rear end gear ratio question

Quote:
Originally Posted by 1rippen6 View Post
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.........
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Old 10-15-2018, 05:42 PM   #12
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Re: rear end gear ratio question

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Originally Posted by HARDCORECASH View Post
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
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Old 10-15-2018, 06:37 PM   #13
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Re: rear end gear ratio question

Quote:
Originally Posted by HARDCORECASH View Post
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.
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Old 10-15-2018, 10:19 PM   #14
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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
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Old 10-16-2018, 06:54 AM   #15
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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.

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Old 10-16-2018, 10:23 AM   #16
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Re: rear end gear ratio question

Had one of those GE clocks when I was a kid
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Old 10-16-2018, 11:30 AM   #17
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Re: rear end gear ratio question

Quote:
Originally Posted by richard2717 View Post
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.....
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