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Flathead Smith · 07-09-2020, 05:58 PM

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.

07-09-2020, 05:58 PM	#20
Flathead Smith Registered User Join Date: Aug 2011 Location: DeArmanville AL Posts: 47	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.