ala.frosty
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For record keeping as much as anything, I'll post what I did here.
I picked up a 14 bolt semi-floating (axle clips) axle with leaf springs attached from a 2500. It has the 13" drum brakes and a 7200 lb GVW. It was billed as having a posi, but there was no G80 code on the RPO sheet. Not surprisingly, when I opened it up, it was an open differential. I then sourced a G80 gov lock from an '88 2500 as a pick yard. The diff fluid looked really clean and had a ton of RTV around the cover, so I figured it had been worked on.
To pull the G80, I had to:
Installing the axle is the reverse of the removal with the following note:
I picked up a 14 bolt semi-floating (axle clips) axle with leaf springs attached from a 2500. It has the 13" drum brakes and a 7200 lb GVW. It was billed as having a posi, but there was no G80 code on the RPO sheet. Not surprisingly, when I opened it up, it was an open differential. I then sourced a G80 gov lock from an '88 2500 as a pick yard. The diff fluid looked really clean and had a ton of RTV around the cover, so I figured it had been worked on.
To pull the G80, I had to:
- Disconnect the u-joint from the yoke
- remove the diff cover (catch the oil as it drips out)
- Remove the drums
- undo the bolt holding the center pin in the diff and set the set-bolt aside
- remove the center pin by rotating one wheel until the pin is horizontal. Reach to the opposite side of the carrier and push the pin toward the rear of the axle/vehicle. Remove the pin and set aside.
- There are two open sides on the carrier. On one side, the centrifugal locker mechanism is visible. Rotate and axle to rotate the carrier to move the mechanism up and the other hole down.
- Put your hand under the carrier opening and push one axle in toward the center of the diff. It should move about 1/2" and the end of the axle will run into a recess in the center block
- The axle clip may fall down on its own, or you might need to spin and wiggle it a bit with the end of your finger. Mine fell down. Some others suggest using a magnet, but gravity worked better for me.
- Repeat the last two steps with the other axle
- DO NOT PULL OUT THE AXLES!
- Undo and remove both bearing caps and set them aside in a manner that will let you know which one goes back on which side. Not that the sides of the caps that face the side of the axle are beveled and the sides that face the carrier are straight.
- Use a thick nail or another convenient device to spin down the holes in the adjuster that was under the right hand cap. This will loosen the carrier. At this point, only the axles are holding the carrier in place.
- With one hand pushing on the carrier to hold it in place, use the other hand to push each axle end out from the axle tube about 8" to 10" until the splined end of the axle falls into the axle housing with a small clunk.
- Place something below the pumpkin housing to put the carrier on once it's out. It is going to drip a bunch of oil and it's heavy -- on the order of 30-40 pounds!
- The carrier is now free, but it's heavy! Use two GLOVED hands on the carrier to pull it out of the pumpkin housing. I prefer to grab the bearing races on each end of the carrier and remove it that way as there's little risk that it'll drop on my fingers that way. Fewer ouchies = better.
- Once the central pin is out, rotate place a hand under the central carrier hole then rotate and axle. Either the carrier will spin, or the spider gears will spin in the carrier, or both. Ideally, you want the a carrier opening to face the rear, and a spider gear to be rotating from the top toward the rear.
- You will get to a point where a spider gear and the shim above it, can be removed by hand. Remove them and set them aside
- Rotate an axle the opposite direction so that the bottom spider is coming up toward the rear. At some point, you will be able to pull it and the spacer out toward the rear. Set them aside.
- Now, the clips will sit inside the bevel gears that are splined onto the axle. Push one axle in toward the carrier, one at a time, and retrieve the axle clip and the bevel gear. Set them aside. Repeat for the other axle. Do NOT push the axles out.
- Continue with the remaining steps above after the clip removal step
- Replace the axle seals (about $12 each) One of mine was very bad and the other was very slightly bad but I could still see oil on the axle shaft and pooling on the bottom of the seal. The bad one had coated the drum and brakes with oil.
- Replace the wheel cylinders (about $12 each) even if yours look good. This is the perfect time to save yourself from having to open this all up again in the not-too-distant future.
- Consider replacing the drum brake shoes. The long shoe goes to the rear. Do NOT put two long shoes on one side and two short shoes on the other side of the truck.
- Wipe the inside of the carrier clean and remove as much metal from the magnet as possible. Place the carrier shim(s) on the left side of the carrier.
- Put the carrier and bearing races in place and hold it there and slide the axles back in to hold it in place.
- Spin the carrier adjuster on the right hand side of the carrier (with all the round holes in it) down to hold the carrier tight. It should finish up about where you started.
- Check the ring gear mating pattern with the pinion gear. Ideally, this ends up in the middle of the gear face with about 0.005" of ring gear backlask. If you don't have this, you will need to reshim the carrier with shims to the left side of the carrier.
- Use a new utility knife or razor edge to clear off old RTV from the mating surfaces of the cover.
- put a layer of black gasket-maker RTV on the cover and install the cover
- Add gear oil (80W90). About 2.25 quarts
- Securely block both the front wheels fore and aft (4 blocks).
- Loosen the 21mm nuts on the axle shock mounts and the front and rear leaf spring frame mounts. You will pull the shackles off with the leaf springs.
- Run the nuts out so that the ends are flush with the bolt ends Do not attempt to remove the bolts.
- Loosen the wheel lug nuts.
- Remove the 13 mm bolt that holds the parking brake cable to the top of the axle. Lift the parking brake bracket out of the way and put the bolt/nut back in the axle hole for safe keeping.
- Remove the 13 mm bolt that holds the axle breather to the brake flex line bracket. Drop the hose and turn the bolt a few turns back into the bracket for safekeeping
- Remove the u-joint completely from the yoke and from the drive shaft. Place the retaining straps and bolts back into the yoke for safekeeping.
- With the wheels on, lift the body up by the axle pumpkin until the wheels are clear of the ground.
- Place supports under the frame just to the rear of the cab immediately in front of the spot where the frame changes direction from flat to go over the rear axle.
- Remove the wheels and drums.
- Disconnect the intermediate parking brake cable from the front cable (just below the cab door). Spray a lot of PB Blaster on the threaded parking brake adjusting mechanism for the passenger-side cable, about 12" to the rear of the join between the front an rear driver side cable.
- Remove the parking brake cables from the drum. It is difficult to describe how to get the cable end free from the parking brake lever inside the drum brakes without further disassembly, but it can be done. Alternately, pull the rear shoe off and then it's easy to remove the cable end from the lever.
- Remove the parking brake cable from the backing plate by pushing in the three tabs and pulling it out. Do NOT cut the parking brake cables; you will need them later.
- Lower the rear diff until the truck is supported on the front tires and the axle stands behind the cab. The axle should hang free.
- Jack up the pumpkin about 5mm so that the jack supports the axle
- Remove the bolts holding the shocks onto the axle. Replace the bolts in the shock mount ends for safekeeping.
- Remove the bolts holding the front of the leaf springs to the frame. These should knock through fairly easily. If you have trouble, a 4" x 3/8" socket extension and a hammer are your friends! Repeat with the other side.
- Place some wood under the axle end plates and lower the axle onto the wooden platform.
- Cut two fingers off of a vinyl or latex glove and get two small elastic bands.
- Place a catch basin below the union between the flex line to the axle and the hard line on the frame bracket.
- Use a 5-sided 14mm line wrench to break the brake line end fitting free from the flex line end. Now, use a regular 14mm wrench to undo the fitting from the flex line. Brake fluid will drip into the catch basin.
- Once the hard line is free from the flex line, place the glove finger over the end of the hard brake line and use an elastic to secure it in place. This will reduce the amount of hydraulic fluid lost during the rest of the work and enable you to remove the catch basin from the work area.
- Remove the securing nut that holds the flex line onto the frame bracket.
- Use the same latex finger trick on the end of the flex line to prevent more lost hydraulic fluid messiness.
- Remove the catch basin from the work area and clean up any drips.
- The bolts are the rear of the shackles should be all that now holds the axle to the truck. Remove one bolt completely. Have a helper hold the front of the leaf spring at it's current height so that when the final bolt is removed, the axle does not roll anywhere out of control. Remove the final bolt holding the last leaf spring to the truck.
- Remove the wood stack by lifting the axle a bit, then lowering it again. Brute force, levers, or rope under the axle and to the leaf spring mounts can help with this. I used brute force and lifted the axle while a helper removed the wood. It's very heavy! Do NOT try this unless you know you're really strong! It will help to leave a wood rail in place under the backing place to slide the axle with the pumpkin off the ground.
- slide the axle *forward* so that the shackles move ahead of the frame mounts 4-6"
- Roll the axle backwards so that the rear of the leaf springs drop below the frame mounts.
- With a helper balancing the axle and moving the wood rails about, slide the axle rearward with the rear of the leaf springs low enough that they can get under the bumper. To do this, I tied some rope around the leaf spring ahead of the axle and pulled it backwards.
- Once the rears of the springs have cleared the rear bumper, roll the axle forward so that the front of the leaf springs can get under the bumper. Once the axle is out from under the truck, slide it out of the way.
Installing the axle is the reverse of the removal with the following note:
- Do not forget to re-attach the parking brake bracket to the passenger side shock mount. Note that the parking brake cable runs above the shock. if you forgot this during the install, disconnect the shock, move the cable above the mount, and re-attach the shock.
- The parking brake cables will need adjustment.
- Loosen the parking brake bias adjustment mechanism (beside the frame rail a couple of feet back from the driver's door).
- Either finagle (tm) the parking brake cable ends into place in the replaced axle without disconnecting the brake hardware, or, if the brakes are apart anyway, with the brakes apart.
- Tug on the parking brake cable beside the frame a few times to check that the cable ends are securely attached to the parking brake lever in the drums.
- Adjust the drum brake mechanism so that the drum goes onto the axle readily, but that any further adjustment would prevent the drum from going on easily.
- Install both drums.
- Hook up the front parking brake cable to the rear below the driver's door, if possible. If not possible, you will need to loosen the bias first.
- Most likely, the bias will prevent you from hooking up the brake cables. Loosen the bias by holding the end of the threaded adjuster with a small wrench (I used an adjustable wrench) and turning the nut on the threaded rod that you used PB Blaster on earlier. Spray additional PB blaster on it to make it easier to turn. It will be difficult to turn!
- Run the nut adjuster down the threaded rod to lengthen the cable between the adjuster and the drum. This will shorten the amount of exposed threaded rod ahead of (in front of) the adjusting nut. Turn the nut so that the threaded rod moves (slowly) toward the rear of the truck.
- At some point, (in my case, with about an inch of the threaded rod still showing), there will be enough slack to reconnect the front cable with the rear cable below the driver's door. Reconnect the cable. The parking brake should now activate the driver's side parking brake.
- Push down the parking brake a little bit and check for friction on the driver's side drum. You want to feel a bit of friction, but not enough that you can't turn the drum, or so little that the brake is not activated. If you've applied the parking brake a few inches and there's no friction, then re-adjust the drum brake mechanism and repeat.
- Once there is some friction on the driver's side drum, check the passenger side drum for friction. If the drum is locked up, reduce the parking brake cable length between the adjuster and the drum by turning the nut on the threaded adjusting rod and moving the rod to the rear. Conversely, if there is no friction on the drum, adjust the nut in the other direction.
- When both drums have approximately the same friction resistance to turning with the parking brake slightly set, then the bias adjustment is complete.
- Release parking brake, then with the brake release pulled, pump the parking brake a few times to verify proper activation and release.
- Release the parking brake lever in the cab and check that both drums wheels spin freely and equally. If one does not, adjust the drum brake mechanism on the wheel that is not spinning freely.
- Lift the truck by the axle pumpkin and remove the axle stands from below the frame.
- Put the wheels on the truck with all lug nuts.
- Lower the truck to the ground and tighten up the lug nuts. Now that the suspension is loaded, the parking brake lever may have become partially activated. Lift the truck off the wheels by the axle pumpking.
- With the parking brake lever in the cab fully up, check that the wheels "spin" (rock a few degrees in each direction) smoothly. If there is friction from the brakes on a side (i.e. not from the carrier or the opposite side wheel), remove the wheel and loosen the drum brake adjustment mechanism. Once both wheels are spinning freely when tightened with the parking brake off and the axle loaded, re-check the parking brake bias. Adjust the bias as needed until a small amount of parking brake application provides approximately equal friction on both sides.
- Pull the parking brake release lever and hold it out while pumping the emergency brake a few times. Check that the wheels "spin" freely. If not, repeat the above brake adjustment process.
- Bleed the hydraulic brake lines and check that they are working properly and not leaking, especially at the union between the flex line and the hard line that you had apart earlier.
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