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GM used Dana 60 rears?
- Thread starter 76zimmer
- Start date
Yes - nowhere near as common as the Eaton HO52/72’s in the 67~72’s but they were available - especially if a lower numerically gear ratio of 4.11 was required because the Eatons didn’t go less than 4.11’s.
According to some footnotes in the GM Heritage files the D60 was mandatory when the 402 option was used - IIRC it was a ratio availability reason.
Also GM was try’n to be more civilized and offer an optional L/S ( Powr-Lok’s ) in the C/K-20’s that the Eatons didn’t offer ( either open or NoSpin ).
With the introduction of the ‘73 models and the Eaton “JR” a.k.a. 14Bolt that offered as low as a 3.21:1 gear and the Gov-Loc there was no need for the D60 rear axle option anymore.
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So here’s an interesting fact. In the trucks built ‘72 and prior, GMC typically used Dana axles while Chevy used the corporate 10 and 12 bolts on the 1/2tons and the Eaton on the 3/4 tons.
GMC did use a Dana 60 in 1/2 tons as a 6 lug semi-float version and a Dana 60 full float version on 3/4 tons.
GMC did use a Dana 60 in 1/2 tons as a 6 lug semi-float version and a Dana 60 full float version on 3/4 tons.
I’ve heard about the GMC six-lug half-ton rear axles since the 80’s but never have run across one - I wonder if GMC had a contract with Dana to use their products for a certain amount of production ?
Yes, I have one I pulled from a 72 c20.
8 lug full floater 4.10 ratio
Back then GMC and Chevy were closer to two separate companies than they ever were. GMC had separate engineering staff and even had their own engines in earlier trucks like the 302 straight six or the big block v6 engine (plaid valve covers anybody?).
I’m not sure the reasoning why GMC used Dana axles, but they did. But by the Squarebodies came along in 1973 the Dana rear axles on GMC went away.
GM should’ve stuck with the S/F D60 instead of the 12Bolts that were introduced in ‘64 - that would have made for a nice half ton running gear setup!
Those 270’s & 302 in-lines and 305 & 351 V-6’s were true work horses - just imagine if GMC would have put the bigger 60 degree series motors in the smaller trucks - that would have been great.
For 1960-66, all GMC 3/4 tons had 4.10 Dana 60 rear axles with leaf springs when Chevy was running Eaton axles with 4.56 gears and coil springs. 67-72 leaf springs and Dana 60 rear axles became an option for Chevy and Eaton/coil springs became an option for GMC.
All those 60’s & early 70’s era rear D60’s were/are a great place/source to find Powr-Lok housings and parts - usually have to swap out the 16-spline or 30-spline side gears though.
Slap a set of D80 T/L 35-spline side gear and clutches-n-steels in and ya can triple the friction surfaces and make em very durable and effective.
Slap a set of D80 T/L 35-spline side gear and clutches-n-steels in and ya can triple the friction surfaces and make em very durable and effective.
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I have seen a couple of the 6 lug versions. And I had heard that the main problem was accelerated wear of the axle splines due to the low number of splines. And most wouldn't pay for custom axles back in the late eighties and early nineties to keep semi-float and go to more splines. I am assuming that the lengths were not the same any other application, not just the 6 lug difference.
I had a '70 C20 GMC, big block camper special, which had the D60.
I’m interested in seeing a picture of a GMC 1/2-Ton with a semi-floater six-lug rear axle in the truck from ‘60~’72.
I’m not doubting that the S/F ones don’t exist it’s just that I’ve been in the truck hobby game for many many moons and have never seen one and I’m fairly good at paying attention to drivetrain details.
I went and took a pic of the only pre ‘73 GMC leaf sprung 1/2-Ton that I know is original and it has a normal 12-Bolt in it.
If anyone has a pic of an unmolested 1/2-Ton GMC with a S/F D60 six-lug please post up a pic ?
I’m not doubting that the S/F ones don’t exist it’s just that I’ve been in the truck hobby game for many many moons and have never seen one and I’m fairly good at paying attention to drivetrain details.
I went and took a pic of the only pre ‘73 GMC leaf sprung 1/2-Ton that I know is original and it has a normal 12-Bolt in it.
If anyone has a pic of an unmolested 1/2-Ton GMC with a S/F D60 six-lug please post up a pic ?
The one 6 lug truck that I looked at years ago, was a GMC, 4 speed, 402. I could have bought it, but it was sporting added cab lights and functional air horns, with aftermarket west coast mirrors.
That was too much for me to undo, in my mind, at that time. I already had a small block C10 that was fun, so why go through all of that work for a 402 to drain my wallet more?
That was too much for me to undo, in my mind, at that time. I already had a small block C10 that was fun, so why go through all of that work for a 402 to drain my wallet more?
I assume that was a C-20/25 truck or was it a 1/2-Ton ?The one 6 lug truck that I looked at years ago, was a GMC, 4 speed, 402. I could have bought it, but it was sporting added cab lights and functional air horns, with aftermarket west coast mirrors.
That was too much for me to undo, in my mind, at that time. I already had a small block C10 that was fun, so why go through all of that work for a 402 to drain my wallet more?
It was a 1/2 ton. Quite the redneck fantasy! No CB antennas, well, not when I looked at it. A coworker's grandpa owned it.
The other axle was another big block 4 speed truck in Montrose, Colorado. It trashed a wheel bearing and axle from being used and abused on a farm.
Both were 6 lug 1/2 ton, drum front brakes. Didn't have cell phones back then to take pictures at an instant.
I am guessing that it was possibly a GMC, big block with 4 speed thing.
My Dad bought a '69 Chevy, 396, TH400, 1/2 ton from the original owner, whom I knew. It has a 12 bolt rear.
My Dad bought a '69 Chevy, 396, TH400, 1/2 ton from the original owner, whom I knew. It has a 12 bolt rear.
As I was reading your response I was thinking the same thing - it would make sense that the 1/2-Ton big-block 4-spd equipped trucks would get the upgraded rear end.
Good info !
Didn’t they have small axle shafts? I remember years ago someone getting excited about finding one and then not so much when they found the internals were smallish.
Yep - corse 16-spline and small 1.31” 30-spline after 1969 ( same size as D44 stuff ).
The benefit was a nodular chunk, strong L/S, a 9.75” ring gear diameter and no c-clips - axles weren’t any better then the older pre ‘64 drop out chunk or 12 Bolt stuff that replaced it.
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