Dana 60 rear end

[Gryffon]

I have a 70 c20 with a 4:56 Dana 60 rear end. Can any body tell me if it possible to go a 3:73 easily?
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[LockDoc]

Originally Posted by Gryffon

I have a 70 c20 with a 4:56 Dana 60 rear end. Can any body tell me if it possible to go a 3:73 easily?
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Does it have leaf springs or coil springs in the rear?

LockDoc

[Gryffon]

Originally Posted by LockDoc

Does it have leaf springs or coil springs in the rear?

LockDoc

It has leaf springs. And now that you mention that it has six on one side and eight on the other. It appears it's been that way for a long time. Do you know of any reason for that?
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[LockDoc]

Originally Posted by Gryffon

It has leaf springs. And now that you mention that it has six on one side and eight on the other. It appears it's been that way for a long time. Do you know of any reason for that?
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That seems like a lot of leafs. Possibly a couple of the leafs on the short side broke at the center bolt and fell out. You should be able to replace it with a 3.73 but I'm not sure which rear end you would have to use. I'm not that familiar with the leaf spring rears.

LockDoc

[Gryffon]

Originally Posted by LockDoc

That seems like a lot of leafs. Possibly a couple of the leafs on the short side broke at the center bolt and fell out. You should be able to replace it with a 3.73 but I'm not sure which rear end you would have to use. I'm not that familiar with the leaf spring rears.
thank you
LockDoc

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[kwmech]

Sure it is a 60? if so swapping to a 3.73 will require a carrier change. 4.56 in a dana 60 is a little unusual unless they were put there or special ordered. Got a pic of the rear of the diff?

[Gryffon]

Originally Posted by kwmech

Sure it is a 60? if so swapping to a 3.73 will require a carrier change. 4.56 in a dana 60 is a little unusual unless they were put there or special ordered. Got a pic of the rear of the diff?

I can take a pick but I''m pretty sure. It is a camper special if that makes a difference?
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[jocko]

custom camper does not make a difference, i.e. it does not mean you got one or the other rear automatically.

[Gryffon]

Originally Posted by jocko

custom camper does not make a difference, i.e. it does not mean you got one or the other rear automatically.

Thank you, I'm new to these trucks and not much of a mechanic. I've had this three weeks try to make some improvements.
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[davepl]

Originally Posted by Gryffon

I have a 70 c20 with a 4:56 Dana 60 rear end. Can any body tell me if it possible to go a 3:73 easily?
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Nope. At least not without a new carrier. The "carrier break" on a Dana 60 is 4.56 and up (or 4.10 and down). So if you had anything lower, you could have. But from my reading of the charts, you've got the bigger 2.420' height carrier.

http://www.differentials.com/technic...carrier-breaks

- Dave

[jocko]

Originally Posted by Gryffon

Thank you, I'm new to these trucks and not much of a mechanic. I've had this three weeks try to make some improvements.
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so, in a nutshell, it's not as simple as a ring and pinion swap. As pointed out, the whole carrier that would accommodate the 4.10 and below (thanks davepl) would have to be swapped in. Sometimes easier to swap the WHOLE rear end, incl leaf, etc if you can find another one with a desired gear ratio. One thing to note - 3.73 was not a ratio option on the 20s (3/4 tons), it's more of a 1/2 ton thing. Big blocks with a D60 rear came with a 3.54 ratio, small blocks generally got 4.10 or 4.56. Different things were standard depending on what was ordered with the truck, engine 6, small block, big block, etc - and C vs K 10/20, etc.

If your goal is lower rpm on the highway, which is the common complaint iwht a 4.56, and even a 4.10, then you do have other options. You can swap the whole rear to another type, but then all your brake lines, etc will need to be redone - so I don't recommend this route. If you can find a leaf spring D60 that was behind a 402 truck - it would have come with a 3.54 and this is a good swp to do - but you do give up some of the tree stump pulling torque multiplication. All depends what you want to do with the truck. As you go up the scale in $ invested... you can swap to an o/d trans, 2004R or 700R4, but they should be gone through and beefed up a bit for HD use. Or, you can keep what you have and add a gear vendors over/unde3r drive unit and shortened driveshaft, a great heavy duty combo (any trans will be the weak link compared to a gv o/u drive), but it is a pricey route to take, >$2K for new parts. Anyway, let us know what your goal and budget is with the truck and folks can help provide some solutions. Sometimes doing nothing is the best route - yes, you scream down the highway (rpm-wise) at 50 mph, but to make up the gas mileage of a g/v o/u install, you'd have to drive the truck for 80 years to pay it off.... (there is no scientific investigation to support this claim... )

[jocko]

Sorry I don't have the reference for 70, but this is for 69 - should be the same. Red box shows available factory ratios. Generally speaking, you would have the 4.57 with a 6 cyl (or manual trans), I believe - this brochure isn't flagged as well as later ones for correlated footnotes. Anyway, optional were 4.10 (which was also standard with a V8) and you could ALSO get a 4.56 optional (even with the V8). That may be what you have. Is anything called out on your SPID in the glovebox? If not, then you should have the standard ratio for the engine that came with the truck. Note that the 3.54 (which was D60-only) is on the same line as the 4.56. My assumption is that the 4.56 was the optional D60 ratio. HO rears were 4.57 or 4.10. Let us know a little more about your truck - SPID picture would go a long way - from that we can decipher original engine and trans and corresponding rear gear ratio, unless a special order was made - which would also be depicted on the SPID.

[Gryffon]

Originally Posted by jocko

Sorry I don't have the reference for 70, but this is for 69 - should be the same. Red box shows available factory ratios. Generally speaking, you would have the 4.57 with a 6 cyl (or manual trans), I believe - this brochure isn't flagged as well as later ones for correlated footnotes. Anyway, optional were 4.10 (which was also standard with a V8) and you could ALSO get a 4.56 optional (even with the V8). That may be what you have. Is anything called out on your SPID in the glovebox? If not, then you should have the standard ratio for the engine that came with the truck. Note that the 3.54 (which was D60-only) is on the same line as the 4.56. My assumption is that the 4.56 was the optional D60 ratio. HO rears were 4.57 or 4.10. Let us know a little more about your truck - SPID picture would go a long way - from that we can decipher original engine and trans and corresponding rear gear ratio, unless a special order was made - which would also be depicted on the SPID.

Thanks for the information, sounds like the D60 w/ 3:54 is my best option. I don't mind giving up a little torque for a little more mileage. This truck has a 383 in it and the 4:56 is a little much. I've always wanted a 67-72 long box pickup and this one was in great shape so I figured I would Lear as I went and I have time to do it but the budget is limited. I'm looking to make improvements on a budget. This is a great forum I appreciate all of the info
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