Rear Axle Ratio Charts For 1967 - 1972 GM Trucks

[LockDoc]

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I have saved these from different places so they don't match each other. I saved them as image files and they are all different resolutions and sizes. They really need to be typed into a document file so the size and style of font matches on all of the charts. Unfortunately I don't type good enough to do that so we will try it this way. I just hope they are all readable with the image size restrictions for the board. I think I have them sized close to the maximum that the board allows. Disregard the C14 designation in the '67 chart, it should be C10.

In case someone is thinking Photobucket or some other photo hosting service, I won't do that for two reasons. One, I am not going to sign up for an account & Two, If the photobucket account is ever closed the thread will be worthless because their won't be any pictures of the charts in it, just empty boxes ...

Thanks.

LockDoc

[LockDoc]

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This is the last Chart. It looks like they are mostly readable. A couple of them may be a little blurry.

There is no guarantee of correctness or completeness (is that a word?) in any of these charts

Edit: I might as well add this chart to the thread too.

Rear Axle Ratios

Ratio 2.56:1 - Tooth Combination 41,16
Ratio 2.73:1 - Tooth Combination 41,15
Ratio 3.07:1 - Tooth Combination 43,14
Ratio 3.08:1 - Tooth Combination 40,13
Ratio 3.08:1 - Tooth Combination 37,12
Ratio 3.31:1 - Tooth Combination 43,13
Ratio 3.36:1 - Tooth Combination 37,11
Ratio 3.42:1 - Tooth Combination 41,12
Ratio 3.55:1 - Tooth Combination 39,11
Ratio 3.73:1 - Tooth Combination 41,11
Ratio 4.10:1 - Tooth Combination 41,10
Ratio 4.11:1 - Tooth Combination 37,9

The tooth combination numbers will be found stamped into the ring gear when you take the back cover off.

They may not all be for the trucks.

LockDoc

[bruceman1968]

Nice job LocDoc, thanks for posting those.

[special-K]

This is great! I'm thinking this is for Chevrolet with the 10,20,30 designates. And,I don't see any posi for K/20,only No-Spin. A Dana 60 would have the Power-lok. It shows a 4.11 for K/20,which is the Dana 60,

[Hawghauler]

Thanks LockDoc!



I'm sure many people will be less confused. Now there is a place to direct people searching for that elusive code!

[LockDoc]

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No problem guys. It might be nice to have them all in one place. I added some info to my 2nd post also.

LockDoc

[sambudo]

where can you find these codes on the axel?

[LockDoc]

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Usually on the passengers side axle tube. Just use the first 2 or 3 letters which ever it has.

LockDoc

[Keith Seymore]

Originally Posted by LockDoc

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I have saved these from different places so they don't match each other. I saved them as image files and they are all different resolutions and sizes. They really need to be typed into a document file so the size and style of font matches on all of the charts. Unfortunately I don't type good enough to do that so we will try it this way.

Thanks for posting those, Doc.

I'm not offended that the fonts and sizes don't match. Lends credibility to the documents, in my way of thinking.

k

[special-K]

I never knew of a 3.36:1 ratio in these trucks. Looks like it was just in Vans. That would be a sweet ratio to swap into a little C/10

[Sandemonium]

Thank you for posting. Great information.

[indianbullet]

Good stuff.

[slikside]

Originally Posted by indianbullet

Good stuff.

Yes, it is. Subscribed.

[Longhorn 70]

I climbed under the truck this afternoon and coudln't find the axle code on the tube. Could they have put it under the spring mount? I REALLY don't want to unbolt the springs to check it.

[swamp rat]

Originally Posted by Longhorn 70

I climbed under the truck this afternoon and coudln't find the axle code on the tube. Could they have put it under the spring mount? I REALLY don't want to unbolt the springs to check it.

Are you talking the front axle? dana 44? that axle stamp is just to the right of the front of the pumpkin towards the upper area..

[LockDoc]

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I don't think it would be under the mount. Sometimes they are stamped pretty light. There may be some that didn't get stamped. If that is the case you would have to pull the rear cover off, check the numbers on the ring gear and use the "Red" chart in post #2...

Example: If the numbers 41 : 11 were stamped into the edge of the ring gear it would be a 3.73 ring & pinion.

LockDoc

[Longhorn 70]

Originally Posted by swamp rat

Are you talking the front axle? dana 44? that axle stamp is just to the right of the front of the pumpkin towards the upper area..

This is for the Eaton HO52 under the Longhorn.


Thanks Leon. It may not have been stamped or these old peepers just didn't catch them. I'll look again from different angles. It may also help to get my 5 year old under there. She sees EVERYTHING.

Thanks for your guys help on this subject. I truly appreciate it.

[LockDoc]

Originally Posted by Longhorn 70

This is for the Eaton HO52 under the Longhorn.


Thanks Leon. It may not have been stamped or these old peepers just didn't catch them. I'll look again from different angles. It may also help to get my 5 year old under there. She sees EVERYTHING.

Thanks for your guys help on this subject. I truly appreciate it.

No problem. Be sure and take a strong light and some coarse sandpaper under with you...

Funny how those kids see it all....

LockDoc

[swamp rat]

Originally Posted by Longhorn 70

This is for the Eaton HO52 under the Longhorn.

Look on top of the pumpkin passenger side of the pumpkin. I didn't think the Eaton had a stamp on the axle, i didn't see one on mine.

[Longhorn 70]

OK I'll look there too. I did see some stuff stamped there.

[FreeRangeChicken]

Okay, here's a total noob question, please don't flame me too badly ...

For 1967 what's a C14 and why isn't there a C10 in the chart? Quick google on 1967 and C14 yielded nonsense. Is that a misprint for C10?

[JointTech]

well since i dont see it yet. I can probably OCR these are convert them to text. Ill fiddle with it today.

[JointTech]

Well my OCR software is kind of crappy but it wont take to much to clean this up. You guys prefer csv, xls or just a text file. the coloms are never going to line up correctly in the forum so it should be a download of some kind.

1967
C14 . (3.73 ratio). HA-MD
C14. (3.07 ratIo). HB
C14 Positraction t3.13 ratio) HC
C14 Overdrive (4.11 ratio) HD
610..... (3.36ratlo) HI
610 (3.73 ratio) (2900 lbs.) Hi -ME
610 (4.11 ratio) (2900 lbs.) HK -MG
610 (4.11 ratio) (2400 lbs.) HL -MF
G10 Positraction (3.36 ratIo) HM-MH
GlO Positraction (3.T3 rallo) HN -MJ
610 Positractlon (4.11 ratio) (2900 lbs.) HO -MK
610 Positraction (4.11 ratIo) (2400 lbs.) HP-Ml
1(10 (3.13 rallo) HQ
PlO (4.11 rallo) HR
P10...., Posltraction (3.73 rallo) HS
PlO (3.l3ratio) HT
C20 (4.57 ratio) HU
C20 Positraction (451 ratio) HV
CZO (4.11 ratio) (Z9OU lbs.) HW
C20 (4.Slratio)DuaI Wheels HX
C20 Positraction Dual Wheels (451 ratio) HY
1(20 (45lratig) HZ-ND
P20 (4.5lratlo) IA
P20 Positraction (4.57 ratio) IB
C30 (4.57 ratIo) LW-MC-MW-MY
C30..... (5.14 ratIo) UJ -MO
C30 (Sl4ratio) IC-MR
C30 Dual Wheels (5.14 ratio). ID-MS-MV
C30 Dual Wheels (5.14 ratio) LV
C30 Positraction (5.14 rIo) lE-MO-MT
C30 Dual Wtieels, Positraction (5.14 ratio) IF -MU
P30 (5.I4ratlo) 1G
P30 Dual Wheels (5.14 ratIo) 1H
P30. . ... Posltraction 5.14 ratIo) II
C30 (4.5lratlo) iN
dO Positractlon (4.11 ratIo) JQ
C20 wP’327” (4.57 ratio) JS
C20 wr’32r, dual wheels (451 rallo) JI
C20 wP’327” (4.11 ratio) (2900 lbs.) JLJ
C30 (4.57ratio) MP
C30 (&lTrallo) MX
P20 (4.llratio) MZ
P30 (4.llratlo) NA—NB
P30 (4. ratio) NC
P30 (6.llratio) NE

[LockDoc]

Originally Posted by FreeRangeChicken

Okay, here's a total noob question, please don't flame me too badly ...

For 1967 what's a C14 and why isn't there a C10 in the chart? Quick google on 1967 and C14 yielded nonsense. Is that a misprint for C10?

I don't see a c14 listed for '67 in any of my literature so it is probably a misprint...

LockDoc

[67chevy1series]

For 67 is c14 3.73 positraction the equivalent to a 67 c10 with 3.73 posi?