What rear end ratio do I have?

[Dmcinfo]

Searched other threads and it looks like I either have 3:73 or 3:08 gears in my 71, auto trans, 4 x4, Blazer. At first, I thought 3:73 was what came from the factory unless you ordered another ratio. However, I've seen a few SPIDs that listed a 3:73 ratio as if it was ordered as an option. Assuming I have the factory stock rear end, what would that ratio be? Thanks.
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[old man jimmy]

3:07's

[Firebirdjones]

3.07's are standard and would not be listed on the spid, however things change after 40 years.

One quick way to be sure is to check the front dana 44 cover. If the tag is still there it will have the gear ratio listed. Assuming it matches the rear that is

[LS6 XAA]

http://coloradok5.com/brochures/1971/blazer8.jpg

It would depend on which engine ur blazer came with 3:73 is standard unless ur blazer came with a 350 which was a option however u could have 3:73's with a 350 if u wanted as a option check ur glove box to c what cha got as far as option's go.

Of course 40 years have passed so who knows for sure whats in ur axle. this link explains what u need to do to know with out pulling diff cover ... just remember non possi gets 2 complete revolutions of tire possi only needs one

http://www.hotrodders.com/forum/way-...io-118376.html

[Burt4x4]

I allways thought 307 came with auto tranny and 373 came with a manual tranny...but no way do I know if I am 100% right.
You could always pull the cover and count the teeth

[Firebirdjones]

Whether it had air conditioning or not can sometimes influence the gear ratio as well.

[SamMargritz00]

my 72 cst had a 350 with the auto and it was 3:73 from the factory. dont know if that helps you any.

[old man jimmy]

this may clear things up.. scanned the page but it wasn't readable after shrinking it. so cropped out the parts for the thread. hope this comes out readable.

[Burt4x4]

THere it is..My 72 SM465 came with 3.73 "Standard". Looks too me everything else was an option...did not know you could get 4.11 from GM!
Thanks OldMan!!

[old man jimmy]

it's hard to read. but on the bottom it says 3:07s were standard if you got the 350 motor.

[joemacho]

i just looked at my spid in the glove box on my 72 gmc jimmy it has 350 v8 with turbohydramatic and 373s gear ratio.

[old man jimmy]

if it's listed on your spid. It was ordered with the 3:73 option. yours would have had 3:07's without a special order. But a lot can change in 40 years.

[rsavage]

If you check your front dana differential it still may have the little metal tag on it on one of the cover bolts. Mine has both the tag stamped 3.07 43:14 and the 43:14 is on the edge of the ring gear. 43 divided by the 14 tooth pinion = 3.07 gear ratio. I have 350 with TH350. If it doesn't have the tag, it would probably be a good idea to pick up some gaskets and change the gear oil in the differentials, especially if it might be 40 years old. Then you would be able to see the ring gear stamping.