CK5 member "POFF" wrote this a long time ago and sent it to me as a Word document, but I thought it might be the basis for a tech article if someone want to add some stuff to it: This document contains information I found while converting my 1970 K-20 to front Disc brakes and a 14 bolt rear end as well as converting my friends ’69 K-5 to 8 lug-3/4 ton. The front disc info is for ’69 and ’70, maybe ’67 & ’68, with open knuckle front axles, although I believe open knuckle axles where not used until ‘69. The rear end swap info is for ‘69-’72 and maybe ’67 & ’68. Dana axles are made by Spicer. In this article I may refer to Dana parts as Spicer. If you go to a parts supplier the new parts will probably come labeled Spicer. There are a few things that you may not have to change on a 71 or 72 that you do need to change on the earlier models. Keep in mind I have only worked on ‘69s and ‘70s, I have salvaged parts off of all years, 60’s-80’s, especially 67-72. When I say, "About" I am estimating. This article is based on assembly only. If you can’t figure out how to take it apart you have no business doing the work yourself. This is not a step by step procedure, it’s a step by step guide to what you need to change and what should fit. Note: I found calling Spicer with any questions to be a complete waste of time. Note: If you have a ½ ton and you want to use 6 lug wheels I would investigate Dana 60s for the rear. Part One: Front Discs (8 Lug) ‘67-’72 ½ tons and ¾ tons came with Dana 44s. The ‘67s & ‘68s have closed knuckle axles. Take these off and scarp them, get a complete open knuckle axle. I don’t believe that K-30s (1 ton 4x4s) existed until ’73. The ½ ton and ¾ ton axles are identical. The only difference is the springs and the brake caliper brackets and out. The first thing you need is a donor front end. I stayed away from 71 and 72 parts because everyone wants too much money for them. ’73 and later K-20s came with either a Dana 44 or GM Corporate front axle. The Dana axles will bolt right up if you desire to do this. I found it easier to convert my existing axle. The later axles do have a better stabilizer shock set-up and a heavy duty tie rod. The GM Corporate axle will NOT bolt up, the spring pads are further apart. Do Not try to use a complete Corporate axle. However, don’t worry, the parts you need for the conversion are the same on the Corporate axles as the Dana 44. Almost all of these parts are still available new from Spicer but expensive! For a ½ ton disc to ¾ ton disc conversion you will need: Spindles Caliper brackets Hubs/Bearings Rotors Master cylinder Booster Master to Prop. Valve Lines Rear Axle (Duh!) For a ½ ton or ¾ ton drum to ¾ ton disc conversion you will need: Outer axle shafts Spindles Caliper brackets Hubs/Bearings Rotors Locking hubs Calipers Master cylinder Booster Prop. valve Prop. valve bracket Brake hoses Brake lines Brake booster brackets (4 pcs with a pin and 2 braces. Used only) Rear brake line bracket If you are converting a drum brake ¾ ton to discs you will need locking hubs. If you are converting a ½ ton to ¾ ton you may be able to use your existing locking hubs. Everything in this conversion bolts bolts right up. You will need to drill one hole. First step: Axle Shafts While it’s apart check to see if you have heavy duty inner axle shafts. If you do not have heavy-duty (late) axle shafts, I highly suggest getting them! The light-duty (early) axle shafts break easily. All trucks ’72 and older came stock with light-duty axle shafts. (Mine had Light-duty axles, my friends Blazer happened to have one of each) Axle Differences: Light-duty (early): The outside diameter of the splines will be larger that the axle shaft diameter. Heavy-duty (late): The out side diameter of the splines will be smaller that the axle shaft diameter. If you put these axles side by side there is a significant difference. There is a good ½" difference in axle diameter. Dana and GM Corporate axles use different inner axle shafts, but both use the same outer axle shafts. Always replace the U-Joints. They are only $20 apiece and it’s a lot more work to change them later. ONLY USE SPICER U-JOINTS! Nobody else’s u-joints come close to the quality of Spicer. Second step: Spindles The difference between drum and disc spindles: (These differences are only about 1/8") Disc: thinner flange Drum: thicker flange There are two different spindle designs for disc brakes. They are identical except one has needle bearings inside and one does not. Make sure yours have bearings, the axles will last longer. New spindles will have bearings. Spicer makes a kit with a replacement bearing, seal and thrust washer. You cannot put a bearing in a non-bearing spindle (You may be able to machine them but unless you’re a machinist it will probably be cheaper to replace them).. Third step: Caliper Brackets The rotors are 1"-2" larger in diameter on a ¾ ton than a ½ ton, therefore so are the caliper brackets. There are several different caliper brackets from ’71 to ’87. They should all have the same bolt patterns and all work. I used the full circle, on piece, bracket/dust shields off of a ’79 Suburban. The 71/72 brackets are really small brackets with a sheet metal dust shield. The new Spicer ones are better than the 71/72 brackets with a bigger bracket and small sheet metal dust shield. Some styles are left and right, some are the same left and right, the new Spicer ones are the same for both sides. Fourth step: Calipers The calipers are the same for ½ ton and ¾ ton. They are different on later models, after ’75 or something. The bolt pattern is the same so I don’t know the difference. I used ’71 calipers on mine. Use ’74 and later caliper pins. These pins have an Allen hex instead of a hex bolt. They are lower profile than the earlier ones. Usually the calipers will come with two different bushings. Use the short bushing with the late pins. Make sure the bleeder screw is on top. The parts store I bought mine from had the left and right switched in the computer. Fifth step: Brake Hoses I used the Sky-Jacker steel braided hoses. They are very nice, they have a vinyl coating, they’re DOT approved and can be bought in different lengths based on your lift. They are about the same price as stock hoses from Raybestos. Make sure you get the newer ones, they just started coming with an adapter to use the factory nut to hold the lines to the frame. The new version is the same price as the old. DO NOT over tighten the banjo bolts. Step Six: Brake Lines I got brake lines from Chevy Duty and they have very good customer service. But, you will probably need custom brake lines because of your modification. For the Blazer we found it best to deal with Inline-Tube directly. The guy can be an [I love Jeeps] but if you have patience the price is the same as Chevy Duty and you can get "3/4 ton Blazer lines" at no extra charge. Tell the guy you have a ¾ ton Blazer. Order the normal Blazer set, with ¾ ton master to prop lines and a rear axle line based on your rear-end, the rest will work ok. We have 14 bolts rear-ends in ours. The ¾ ton master and booster stick out a bit more than the ½ ton so you may have to bend the lines a bit at the front but it’s only about 2" and you can’t tell when you’re done if you’re careful. You will have to get the brass fittings at a supply shop, I think NAPA carries these in Weatherhead. They are inverted flare. I think you need a tee and three unions. The front lines are smaller in diameter than the rear. Step Seven: Proportioning Valve The Prop valve is the same for ½, ¾ and 1 tons, 2x and 4x. Chevy Duty has them for $50. They are $120 at the dealer and mine came from Chevy Duty in a Delco box. The Blazer one did not. Why? Don’t know. Doesn’t matter. They both work fine. GM did however go to a 5 way, frame mounted model in ’73, so you need a ‘71/’72 prop valve. Step Eight: Master There were two masters used in the early ‘70s, get the Delco/Morane. There is also a Bendix but it’s different than the ones I’ve seen on stock K-20 4x4s. Step Nine: Booster Available new or rebuilt. Just like the master there is a Delco/Morane and a Bendix. Get the Delco/Morane one. Don’t play with the push rod adjustment unless you know what you are doing. I don’t so I left it alone and it works fine. Step Ten: Booster Brackets My knowledge is a bit limited on these. I know a K-20 with power discs bracket set up will work. I think any truck with power disc brakes will work. You can do what I did and find someone with a K-20 with stock disc brakes and look. A Polaroid camera is handy too. There are two brackets with a pivot pin, two levers and two support brackets. The brake pedal to lever adjusting rod should be the same if you already have power brakes. I have included the picture I used for the bracket locations. The smaller round bracket is easy and bolts to existing studs (parking-brake assembly studs). The longer, larger bracket needs a hole drilled in the fire wall. The exact location of this hole doesn’t matter as long as it doesn’t get in the way of anything. I measured the one on a guys ‘72. (Bone stock ’72 K-20 Longhorn! His dad bought it new in ’71!) Based on further research, the booster brackets and the round support can come off of any truck with disc brakes. The lower support bracket has to come off of a ¾ ton, the ½ ton one is about 2" shorter. Step Eleven: Hubs I think the bearings for a K-20 are all the same after ’71. But, to be safe do what I did and get bearings to match the year of the truck you got the parts off of. If you bought new stuff, the same place will probably give you the right bearings. Write down the part #s of every thing you buy or change. Step Twelve: Locking Hubs If you convert an early ¾ ton you will have bulky bolt on locking hubs. Just go down and get some Warn hubs. The front axle I got my stuff off of had Warn hubs already so I bought them. Stock ones are probably fine. The later ¾ ton locking hubs are the same as the earlier ½ ton locking hubs. You can get what ever brand of locking hubs you want, I have no preference. I installed the snap rings on the otter end of my axle shafts, I have been told these are not necessary, you make the call. Step Thirteen: Rear Brake Line Bracket You may only need this if you truck originally had drum front brakes. Both of our trucks did so we needed it. You have to get this off of a ’71 or later 4x4. Take a cordless drill to the junk yard or you’ll be all day trying to chisel it off. Just bolt it on your truck. I believe there are a couple different styles, so get one to match your brake hose or get a hose to match the new bracket. A hose is a hose if it has the right size connections. If your hose is a little short you can compensate by putting a spacer between the bracket and the frame. We did this on the Blazer and it worked well. The brakes lines can be bent a few inches without causing any problems. Part Two: Rear Axle (14 Bolt) There are many different axles available that will work fine in your truck/Blazer. I chose the GM 14 bolt with a 10.50" ring gear. They are bullet proof, plentiful, parts are cheap and lockers are cheap. Many people will argue for the Dana 60 or Dana 70, that’s fine, if that’s how you feel, buy a Dana. From what I’ve read the axles are in this order starting with the strongest- Dana 70, 14 Bolt, Dana 60, if you can find a Dana 70 and you can afford it you can afford to pay someone to put it in. However, 14 bolts are cheaper and easier to find. If you want a 14 bolt conversion read-on. Step One: Selection I think any year 14 bolt will work. There were some 9.50" ring gear 14 bolts made at some time, these are not desirable. I believe you can tell the difference because the 10.50" ring gear rear ends have a bolt on pinion housing. Avoid the semi-floating 14 bolts like the plague! A 4wd axle is preferred but a 2wd axle will work, the shock mounts are different and the spring pad angle may vary (not sure about the spring pad angle). I chose an earlier axle because the brake system on an early ‘70s truck is more similar to a stock 71/72. I got a ’73 for my K-20. I would suggest a ‘74-’77 with 11" brakes. Some ‘71s and ‘72s may have come with 14 bolts, I would avoid these, when more than one rear-end is offered in a year it’s harder to deal with parts stores and junk yards want more money for pre’73 parts, even if the same part was used in ’73 or later trucks (any one with a ’70 with stock disc brakes has probably run into this problem at the parts store). Unless you are going to tow a lot of really heavy trailers I wouldn’t get the 13" brakes. The 11" brake parts seem to be easier to get and cheaper than the 13" parts. I have 11" brakes and they are more than sufficient. The Blazer has 13" brakes and they were more expensive than mine. The braking surface with 11" brakes is still 6 square inches larger than stock, 71/72, ¾ ton brakes. Something I didn’t know when I did mine: Beginning in ’73 the ¾ ton, 14 bolts have 42 ½" spring pads; The 1 ton, 14 bolts have 40" spring pads. My truck and the Blazer have 40" spring pads. We got ¾ ton rear ends and had the spring pads moved. This cost about $100 and may end up to be the best alternative. But, you may be able to save some money and hassle by finding a 1 ton. Note: Most of the 1 tons probably have 13" brakes- it’s your call on price vs. easy. Step Two: Shocks Moving the shock mounts cost about $60. 2wd rear ends have different shock mounts than the 4wd. If you get a 2wd rear end (like we did for the Blazer) cut the shock mounts off your self and shorten them with a torch, grinder, saw etc. to match your stock ones. The side to side location is more important than the up and down position. If you go to a good off-road shop to get your shocks they will measure your shock mounts rather than guess based on your lift. If you truck is lifted I would weld the shock mounts on so they don’t hang down past the axle tubes, thus they won’t be as likely to hit rocks. Step Three: Brakes The ’73 is the only year to use the large inlet diameter wheel cylinders. In ’74 they went to the smaller size inlet on the wheel cylinders, these are easier to find and cheaper. You will need a brake hose and the axle brake lines for the same year rear-end. Brake hoses for lifted trucks are easy to find using the illustrated parts guides, you can usually look up the correct hose then look in the illustrated guide for the same hose but longer. If you have factory disc brakes or disc brake lines you should be o.k. If you have front drums the brake hose will have to be longer because the rear brake line does not hang down as low as the disc trucks. I converted to discs so I got later lines and A rear brake line/hose bracket off of a ’73 4x4. Try and get this bracket off of the truck when you get the rear end. Your old brake hose bracket is riveted on with one rivet and your new bracket has two holes. You’ll have to drill the old one out. You can use the original rivet hole for one bolt then you’ll have to drill one more hole in the frame. Note on 13" brakes: We used a 13" brake axle on the Blazer and the parts are considerably more expensive. Step Four: Parking Brake If you have a ¾ ton truck you need to use your original parking brake cables. The later trucks (’73 and later) have shorter cables and they won’t reach. If you have a ½ ton you will have to get ’71 or earlier Corporate 10 bolt parking brake cables. If you have a ½ ton get the parking brake cables with the rear end, you can cut the ends off and send them to Inline Tube and they will make you the correct cables. The Blazer and my K-20 long bed have the same length rear cables and front cables, the only difference we could find was the intermediate cable. FYI GM doesn’t make these cables anymore but Inline Tube did a really nice job on the ones for the Blazer. Step Five: Limited Slip If you want a limited slip: I would suggest a Detroit Locker, unless you prefer otherwise. I have a locker in mine and the thing is unstoppable in 2wd. If you want a limited slip, I would not get a rear end with a posi already in it. A Posi that old will probably be worn out. If you want a Locker make sure you get a rear end with a stock, open, carrier. 14 Bolt axles are the only axles that use the stock carrier for a locker. The Lockers are only $300 new. The Blazer is getting a Locker up front, I only wish I had one up front, too. Note on Lockers: They are loud and they clunk! If you don’t mind this they kick ass! DO NOT THROW ANYTHING AWAY UNTIL YOU ARE DONE! Part Three: Sources 1. Chevy Duty Truck Parts 1 Chevy Duty Drive Kansas City, MO 64150 (816) 741-8029 www.chevyduty.com 2. Border Parts 3875 Bancroft Dr Spring Valley, CA (619) 461-0075 3. Inline Tube 33783 Groesbeck Hwy. Fraser, Michigan (800) 385-9452 www.inlinetube.com 4. Snap-On Tools 2801 80th St Kenosha, WI 53143 1-800-866-5748 www.snapon.com 5. OTC Tools SPX Corporation 655 Eisenhower Drive Owatonna, MN 55060 Phone 800-533-6127 www.otctools.com Note on Border Parts: John, the Owner, is a Genus! He knows everything about drivetrain! He’ll pull part numbers, prices and other sources for parts out of his ass! But, you have to have patience, he is really busy. I recommend calling early in the morning and if you live in San Diego County I suggest walking in, it’s worth the drive (and the wait). I did my whole brake and axle conversion and he only had to look one part up in the book! Part Four: Tools (no, this is not an advertisement for Snap-On tools) You will need some special tools for these conversions. Some other tools are just convenient to have. Check out ebay and swap-meets for tools and manuals! Good tools (Snap-On) are almost always worth the extra money and they often save your knuckles and a trip to Sears. Craftsman has a lifetime warranty - Snap-On tools don’t break! I have never broken a Snap-On tool using it correctly. Remember a used good tool is better than a new cheap one! 1. Lock Nut Sockets: If you are doing the front you will need a Dana 44 lock-nut socket, this is a round socket about 3" in diameter and about 5" long with 4 tabs on it. If you are doing the rear you will need a GM rear lock-nut socket, this is a round socket about 4" in diameter and about 2" long with 6 tabs on it and about a 1 ½" diameter tube sticking out the center. They damage easily so spend the extra couple bucks for the Snap-On ones, they are well worth the money! The front one is about $25 and the rear one is about $40. 2. Snap Ring Pliers: You will need external snap ring pliers for the front, there is a snap ring on the end of the axle shaft, this needs to be removed before you can remove the inner part on the locking hubs. Some people leave this snap ring off so you may not find one in there. The rear hubs on a 14 bolt have a snap ring that holds the outter wheel bearing in, if you have the right snap ring pliers you are stoked. I used slip-joint pliers, not Channellocks but the old two-position, straight jaw, slip-joint pliers that you never use for anything else. 3. Hex Key-Allen Wrenches: Get a couple good ones, the ones on the hubs at the junkyard are pretty rounded off some times. Bondhus makes really nice ones, you can get them cheap at www.harborfreight.com. Make sure you have the hex wrench or even better a hex socket for the caliper brackets. 4. Front Hub Snap Ring Removal Tool : AKA- Pieces of broken dip-stick. There is round snap ring inside the front hub that holds the inner part of the locking hub in. To get this out you need a small standard screwdriver and some pieces of dip stick. Take an old dip stick and a pair of dikes and make a cut in the dip stick about 4" from the end. Dip sticks are hardened so all you will make is a dent this is fine, now bend the dip stick and it will break. You should have a little bit of a lip where you made the cut if not you can make one with a hammer. Make about 3 of these. As you stick the screwdriver in between the ring and the hub stick the dip stick pieces in. Work your way around the hub sticking in the dip sticks, you can use the lip to pull the snap ring out 5. Torque Wrench: A Snap-On torque wrench is a very valuable investment. You can use Craftsman or Husky tools for most stuff but nothing compares to the quality, accuracy and ease of use of a Snap On torque wrench. Their dial style and upper-end click type wrenches are awsome. They are $100-$300 but well worth it. 6. Bearing/Seal Driver Set: I can’t believe I did with out for so long! Lisle makes a nice set, machined out of aluminum, fairly durable if you take good care of them. 7. Front Axle Tube Cleaner: Front axles have the oil seals at the inside of the tube (near the carrier). When you pull your axles the tubes will probably be full of dirt. I took a piece of ½" flat stock about 18" longer than the left axle shaft and bent both ends at a 90 degree angle. One end was about 1" long, I then screwed a piece of flexible plastic to the end as a scraper, the other end is about 6" long for a handle. I used one of the old nylon leaf spring bushing things. 8. Manuals: Get the factory Service Manual for the year you get the rear axle from. Any ’71-’79 manual should tell you what you need to know about the front. I got mine for $10 + shipping on ebay. If you are doing an 8 lug-¾ ton conversion don’t bother buying a Chilton manual, they don’t have any info on ¾ ton axles or brakes. 9. Slide Hammer & Spindle adapter: I have a slide hammer but I don’t have the spindle adapter. I want to get one, they are nice to have. You can use a plastic tip or dead blow hammer. Tap the spindle alternating sides and it will eventually break loose. 10. Flare-nut Wrenches: Always a good investment. They save a lot of rounded off brake line nuts. Snap On makes some that have a flare nut end and a really thick open end, nice! The Craftsman and Husky ones are fine though. In Conclusion: If you find any errors in this article or have any questions feel free to contact me at firstname.lastname@example.org. Please feel free to copy this and give it to anyone whom needs it.