60 1/2ton rear end question

[fuelpump]

What rear ends did the 60 1/2 tons come with? I don't believe the standard unit was a 10 bolt DANA 44 but rather a GM 10 bolt but which one?
I believe the truck I just picked up has a 3.90 posi gear in it but I want to go to something lower. I'm running a 307" SBC and a 3 speed stick. I know the optional gear was a 3.37 and ClassicParts carries them but I'm not sure if they will work with the posi unit. Help me firgure out my options. The Richmond web site does not show which GM 10 came in a 60 1/2 ton 2WD. Does anybody know which one it is? Thanks.

[chevytrucknut]

The dana 44 was offered as an option in GMC's with rear coils. I haven't seen them in a chevy yet. I found one for my swb '65 chevy that is on a '62 frame. I didn't like the 3.90 ratio in the GM rear end and the Dana had 3.73's. I did manage to twist the axle tubes out of the Dana. I was able to find another one and it failed the same way. So now I'm using a stock '65 GM corp. 3.73 and its held up great so far. both Danas were out of a '60 GMC with trailing arms and coils rathger than leaf springs.

[fuelpump]

Does anybody know anything about the GM55t rear end? It looks like it was OE from 55-64 on 1/2 ton 2WD pickups. 3.90 or 3.37 only. Is this correct??? If so that would explain why I can't find any other ratios.
http://www.ringpinion.com/DiffDetail...ame%3dGM%2b55T

[badpeanut]

Originally Posted by chevytrucknut

I did manage to twist the axle tubes out of the Dana. I was able to find another one and it failed the same way.

Why not weld the axle tubes to the center section? This is commonly done on the 8.5" ring gear 10-bolt rearends from the '70s to cure this problem. Just weld a little bit at a time 180° apart so things don't get too hot. I've done a few 10-bolts with good results.

[Fred T]

I'm a long ways from an expert on 1/2 ton rears. On these trucks, the stock rear was a 10 bolt with either 4.10, 3.90 or 3.73 (later model) gears. If you have a 12 bolt it is not what came in the truck. The reason I'm saying this is that you're talking 10 bolt, but your link is to a 12 bolt.

One link that I found that is less confusing than Randy's is www.tomsdifferentials.com . Go to his catalog and you will find parts for both rears. You can also buy the parts from places like summit racing, but you have to know what you need.

[Captainfab]

The Randy's link is the correct rear end you have, but they were only used from '55 thru '62. It was replaced by the 12 bolt in '63. As for gear choices as far as I know it's just 3.90 and 3.38's. If you're really wanting higher gears (lower numerically) you will probably have to switch to a 12 bolt.

[fuelpump]

Originally Posted by Captainfab

The Randy's link is the correct rear end you have, but they were only used from '55 thru '62. It was replaced by the 12 bolt in '63. As for gear choices as far as I know it's just 3.90 and 3.38's. If you're really wanting higher gears (lower numerically) you will probably have to switch to a 12 bolt.

Captainfab,
Thanks for confirming what I suspected. Both cars and trucks in 55 to 62 used carrier type rear ends. The original truck ratios were 3.90 and 3.38 and no one that I can find makes any other ratios. Probably because it is not widely used. I guess I'll just look for a used 3.38 gear set and if that doesn't pan out I'll bite the bullet and buy a new set. 3.38 should be a good highway gear for what I am useing the truck for.
Rich

[Demmit_Hemmit's 65]

If that rear end you have has an axle code and is an origional rear from your truck I have a book that tells what your ratio is.................................They are in 2 letter combinations..........................Examples........AW,BW,AX, BX.........................these stamped letters were the 3.08:1 Ratio..........Hemmit

[fuelpump]

Originally Posted by Demmit_Hemmit's 65

If that rear end you have has an axle code and is an origional rear from your truck I have a book that tells what your ratio is.................................They are in 2 letter combinations..........................Examples........AW,BW,AX, BX.........................these stamped letters were the 3.08:1 Ratio..........Hemmit

I'm just gonna do it the old fashin way by jacking up the rear tires and counting the tire and drive shaft rotations. I should be able to tell a 3.90 from a 3.38. Even without a tach its pretty evident in high gear (3rd) at about 40 MPH that the engine is reving pretty high.