KS10 rear end
 

I have this 1963 C20, it has the KS10 No-Slip differential. Can this be rebuilt to a different gear ratio?

I am not sure what ratio it is, however, I may want to get something taller. And, I would like to keep it 8-lug.

Thanks.

Re: KS10 rear end
 

'63 C20 likely has 4.57 gears.

Re: KS10 rear end
 

Any way to change the ratio?

Re: KS10 rear end
 

You can change the entire 3rd member with one with 4.10 gears. That is as high of a gear you are going to find, if you can find one. That is the highest gears ever made for those Eaton HO52/72's. New gears are not available. New drums are not available either.

I would suggest changing the entire differential for a 14 bolt with 3.73 or taller gears.

Re: KS10 rear end
 

1. What is the difference between a 3rd member and an entire differential?

2. What exactly is a “14 bolt with 3.73”? I understand the gear ratio, just what car? I presume you mean an entire rear end from a specific car or truck? What years car or truck am I looking for?

3. Will I need to modify the rear end structurally, for example, adding brackets or supports?

Re: KS10 rear end
 

You'll get faster answers just searching the internet.
I seem to recall the 14b was first used in 75 and much later ones started using metric measurements. Watch out for those. There are semi-floating and full-floating 14bs. Full is better. Yes, spring and shock mounts need changing.

Re: KS10 rear end
 

Third member: https://www.4wheelparts.com/category.../LowPinion.jpg
Here's a guy who did a 14 bolt swap: http://67-72chevytrucks.com/vboard/s...d.php?t=624445

Re: KS10 rear end
 

Thanks.
That looks like a lot of work.

Re: KS10 rear end
 

Maybe I just go with an automatic trans and keep the rear end?

What automatic trans would work?

Will a 700r4 bolt up?

Or, is a TH350 better for the low geared rear end?

Re: KS10 rear end
 

TH350 will not change anything. If you decide to change transmissions, you need to go with an overdrive transmission to drop the revs down. Just a transmission change might not drop the revs enough for your liking, but an overdrive trans with 4.10 gears would be a pretty good setup.

Also, if you decide to keep the original rear and go with some 4.10s, you could have the 3rd member set up by a shop if you didn't want to do it yourself, and you wouldn't have to pull the entire axle from the truck. The pinion and ring gears are set up together in the 3rd member

Re: KS10 rear end
 

I thought the rear end gears cannot be changed.

Re: KS10 rear end
 

Find an 8 lug rear with 3.73 or 3.42 gears. Depending on your use that would be a great combo with your 292.

Re: KS10 rear end
 

If you do not want to go to the work of changing the entire differential, then an OD trans is your only other option to lower your RPM's. A manual trans would be the easiest. If you go with a 700R4, you have the TV cable to deal with. No one makes a kit for a I6 carb to correctly setup the TV cable. You will have to fabricate something with lots of trial and error to get it right. You could go with a 4L60E, but then you will need a aftermarket standalone controller which will set you back about $700, plus another $125 for a TPS kit which will require modification/fabrication for your carb. No matter how you go about lowering your RPM's, it is going to be a lot of work.

Re: KS10 rear end
 

I think the T5 may be a good option.
Or, an SM319 with overdrive.

Now, if only I can find one.

Re: KS10 rear end
 

Here is a link to an sm319 that a member is selling. I have one in my truck and I love it. I have it wired up pretty much the way the factory wired it. Only diversion from factory was to add a relay to keep the HEI module working right

Re: KS10 rear end
 

Thanks.
What do you need to wire? The overdrive solenoid?

Re: KS10 rear end
 

The solenoid, the governor, the relay to energize the system, the kickdown switch, and an additional relay if you are running an HEI. There's also a lockout cable that goes into the dash so you can lock out the overdrive if desired. On my truck, it has a factory dash knob in the location closest to the steering column on the left side.

If you have a 4 speed right now, you would need to find a 3 speed floor shifter for the overdrive or swap out your steering column for a 3 on the tree

Re: KS10 rear end
 

Since I have the 4:56 rear end, how much difference would there be going to a 4:10? Is it even worth it?

Re: KS10 rear end
 

It'll probably drop around 300 to 500 rpm depending on tire size. Search for engine rpm calculator, then plug in what your current setup is and then change it to what options you are going with

Re: KS10 rear end
 

I have 1966 c-20 that had a HO52 rear axle with 4.56 gears. I found a HO72 Third member with 4:11 gears and it was a direct bolt in as far as the axle goes. But I did have to cut about 3/4" off the driveshaft, which I did myself.

See post #13-15 at http://67-72chevytrucks.com/vboard/s...d.php?t=534896

I have had no problems and even drive on the interstate periodically.
If it were me I would find a HO52 (3/4 ton third member) or HO72 (one ton third member) with 4:11 gears and then take out the KS-10 Locker from your differential, and drop into the new differential. If you do not wish to use the locker, there are some here who would buy it from you, including me.

There was also a Dana 60 eight lug used in some trucks (I think only big block trucks) that is a direct bolt-in with the exception of the panhard rod, which is about a foot shorter. I happen to have one, it comes with a boss cast into the pumpkin for the panhard rod and mine came with 4:11 gears. It was out of a 1971 396/Turbo 400 C20. You can put about any ratio you desire in one of those. Some of the C20 Dana 60s were leaf sprung also. A ¾ ton eight lug out of any truck with the appropriate width can be used, and if your truck has coil spring rear suspension and axle does not have a boss for panhard rod you could use one of the kits listed below.

https://www.speedwaymotors.com/1960-...Kit,46251.html

https://www.ebay.com/itm/1963-72-Che...-/172466216108

https://welderseries.ecwid.com/Unive...Rear-p51463697

https://reactsuspension.com/products...2-c10-6372-008

Just so you know, if you have the old style HO52 third member with the double-row ball pinion bearing, a 4:11 ring gear set will not fit. I suspect these third members had a design change around 1967 and started using a double-row taper bearing on the pinion. But I have seen conflicting information on this for example Yukon.

The double pinion may also have something to do with the load bolt design of the HO72...I am not sure. When you go to Yukon gear & axle they show the ball bearing pinion bearing being used on the non-load bolt HO72 from 1960 - 1972 and the taper bearing being used on the load- bolt HO72 from 1960 - 1972. But I think Yukon’s information is wrong.

I have heard that there was a 3:90 ratio available for the HO52/HO72, but I have never seen one. It may have been an aftermarket offering.

Re: KS10 rear end
 

I have never removed a third member, so I am not sure how difficult it is. I would definitely sell or trade my locker for a higher gear third member. Still don't really understand all of this, so I don't really know what I am up against.

Can you tell me which Dana rear end would fit in my truck?
That way I could change to any gear ratio, correct?

Would any welding or mods be required?

Re: KS10 rear end
 

To remove the third member you only need to:

1. Drain the gear oil.
2. Pull the axle shafts out about three or four inches... yours are already removed so no big deal.
3. Unhook drive shaft from axle.
4. Put an automotive floor jack under the third member.
4. Remove the 10 or so bolts on the opposite side of the differential cover.
5. slide out the complete third member and drop down.

It is one of the easier axles to work on.

Finding the 4:11 third member will be your toughest part, but if you do, the install is easy.
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As far as the Dana 60 goes, they were supposedly used in C20s from 1964-72. They were used in both coil spring suspensions (like yours) and leaf sprung suspensions. I originally was under the impression they were only used in big block trucks, but I saw one under a 1967 C20 with leaf springs that was a stock install.

The Dana 60 is a bolt in affair, if you get one out of a coil spring truck and you have the pan-hard rod that come with it... with the possible exception that the drive shaft may need to be modified. If you use the leaf spring version you will need to remove the leaf spring perches and use something like one of kits shown in my previous post.

The great advantage of the Dana 60 is that all parts are readily available, as it is still produced today and it will have the greatest selection of gear sets and differential options.
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There is another option and that is to use a A833/NP833/MY6 transmission in place of your four speed (most likely a Muncie SM420), or one of the more modern 5 speeds used in 1988 and up year Chevy/GMC trucks. The more modern five speeds will have a good gear spread and have an overdrive, which will turn your 4:56 into a ≈3:30 in OD, and really may be your best solution.

About two years ago I went looking for a A833 and actually found two on the same day. The A833 transmission was found in 1980-87 Chevy Trucks/Vans/Step Vans. The aluminum cased version of the transmissions was used for sure in the 2WD 1/2 ton with the gasoline engine. The cast iron version was used in the 4WD (MM7) and Diesel 3/4 ton version (and possibly the 1/2 ton diesel version also). I was able to get both the 2WD and 4WD cast iron version, which I prefer.

Re: KS10 rear end
 

I was just thinking, wouldn’t it be a good setup with a Dana 14 bolt rear end, 3:07 gear AND a T5 5-speed tranny?

Seems like that would be the ultimate over-drive setup.

Re: KS10 rear end
 

If you're planning on running interstate speeds all the time, that would probably work well. Might be a little slower off the line though

Re: KS10 rear end
 

Well, I’m a little too old to be racing stop light to stop light. I’m good with taller gears. Can’t wait to get this thing on the road!