drum brake problems - The 1947 - Present Chevrolet & GMC Truck Message Board Network

krazy_texan · 11-14-2002, 12:54 AM

i am having a lot of trouble removing the rear drums on my '71 custom/20 i have tried several things and they wont come off and i need to change the pads badly as this is my only vehicle and being 18 and on my 3rd vehicle (restored and sold not wrecked ) mom and dad dont like me driving thiers

Patrick Sullivan · 11-14-2002, 01:32 AM

You've probably got the Eaton full floating rearend, in which case you have to pull out the axle shafts to get the drums off. I had more detailed instructions around here somewhere, but I'm not sure where they went..

Fred T · 11-14-2002, 02:55 AM

If it's the full floater axle (8 lugs with a large protuding hub) there are two ways of removing the brake drum. Easiest way is first.

On the face of the drum there are two large slot screws with countersunk head. You need a large screwdriver with a head that fills the slot, I took the largest drive I had and ground the end off until it was the right thickness. You can also try using an impact driver, the kind with a screwdriver bit that you hit with a hammer. Just don't go for the cheap one, you will destroy it immediately. Start by soaking the screws with a good penetrating oil a day or two in advance. Kroil and PBBlaster are the favorites. Removing the two screws should allow you to pull the drum, you will probably have to back off the adjusters to suck in the shoes out of the way.

The second way is to pull the axles. Drain some lube out of the differential first. Remove the 8 bolts in the axle head (on the end of the hub) and the axle pulls out. Then remove the two big nuts that hold the hub onto the axle, they are nested inside the hub around the hollow axle housing. There should be a keeper between them. This will allow you to pull the entire hub/drum assembly, be careful, it's heavy and you can damage things if it doesn't come off or go back on straight. Doing this will force you to replace the oil seal on the back of the hub, if the axle housing has a groove in it you also need a redi-sleeve to go over the groove. This seal is easily damaged when replacing the hub, I recommend that the drum be taken off the hub to lighten things up. If not, get some help to push things back on straight.

The best tool you can get to help with this is the factory service manual, it is full of instructions and pictures.

71GMC_3/4T · 11-14-2002, 06:15 AM

I just did mine a couple weeks ago. If you have the screws out of the drums (assuming you have them), you may need to back off the adjusters like FredT says. To do this, you will need a brake adjusting tool and a small long screwdriver. It helps to know what you are dealing with before you start, so try to take off both drums - you may get lucky with one. The other side will be a mirror image. Get a flashlight and look in the hole. You need to push the self adjuster arm away from the toothed adjuster wheel and hold it there. You then need to back off the adjuster wheel by engaging the brake adjuster and turning it with the brake adjuster tool. Try to turn the drum while you are doing this. If it gets tight, you are going the wrong direction. Either that, or try adjusting it without holding the self adjuster arm. It should turn easily only in one direction. Once you have established that, push in on the arm and go the other way.

While you have the rearend apart, it is also a good idea to put new seals in the hubs and repack the bearings. Get a new diff cover gasket and change the oil too. It will thank you for it by lasting longer... Go to Napa for the gasket. Most of the Checker/Autozone type stores around here didn't know jack about 3/4 tons.

If you're going to disassemble and repack the bearings, you will want to buy the nut keepers, which for some reason, Checker's had(!). If you don't have a 1 5/8 socket, you can tap the nuts loose (after bending the keepers out of the way) but use a drift punch instead of a chisel like the previous idiot did on mine.

When I did mine, one drum was well grooved from the rivets and the other was still fair due to being lubricated by gear oil. They told me they were beyond turning, but I asked them to humor me by just smoothing them up and leaving the grooves. It's an old beater and I couldn't see spending another 100 a side on new drums.

Rebuild or replace the brake cylinders while you're doing this.

Good luck!

11-14-2002, 12:54 AM	#1
krazy_texan Registered User Join Date: Oct 2002 Location: West Des Moines, Ia Posts: 3,233	drum brake problems i am having a lot of trouble removing the rear drums on my '71 custom/20 i have tried several things and they wont come off and i need to change the pads badly as this is my only vehicle and being 18 and on my 3rd vehicle (restored and sold not wrecked ) mom and dad dont like me driving thiers

11-14-2002, 01:32 AM	#2
Patrick Sullivan Transcendental Trucker Join Date: Dec 2001 Location: Rockaway Beach, OR Posts: 374	You've probably got the Eaton full floating rearend, in which case you have to pull out the axle shafts to get the drums off. I had more detailed instructions around here somewhere, but I'm not sure where they went.. __________________ Patrick Sullivan \| sullivan@oregoncoast.com Rockaway Beach, Oregon 1972 Chevy Cheyenne C-20 1998 Dodge Dakota 4x4 So, fill to me the parting glass And drink a health whate'er befalls... Then gently rise and softly call Goodnight and joy be to you all!

11-14-2002, 02:55 AM	#3
Fred T Cantankerous Geezer Join Date: Aug 2002 Location: Bel Aire, KS Posts: 6,264	If it's the full floater axle (8 lugs with a large protuding hub) there are two ways of removing the brake drum. Easiest way is first. On the face of the drum there are two large slot screws with countersunk head. You need a large screwdriver with a head that fills the slot, I took the largest drive I had and ground the end off until it was the right thickness. You can also try using an impact driver, the kind with a screwdriver bit that you hit with a hammer. Just don't go for the cheap one, you will destroy it immediately. Start by soaking the screws with a good penetrating oil a day or two in advance. Kroil and PBBlaster are the favorites. Removing the two screws should allow you to pull the drum, you will probably have to back off the adjusters to suck in the shoes out of the way. The second way is to pull the axles. Drain some lube out of the differential first. Remove the 8 bolts in the axle head (on the end of the hub) and the axle pulls out. Then remove the two big nuts that hold the hub onto the axle, they are nested inside the hub around the hollow axle housing. There should be a keeper between them. This will allow you to pull the entire hub/drum assembly, be careful, it's heavy and you can damage things if it doesn't come off or go back on straight. Doing this will force you to replace the oil seal on the back of the hub, if the axle housing has a groove in it you also need a redi-sleeve to go over the groove. This seal is easily damaged when replacing the hub, I recommend that the drum be taken off the hub to lighten things up. If not, get some help to push things back on straight. The best tool you can get to help with this is the factory service manual, it is full of instructions and pictures. __________________ Fred There is no such thing as too much cam...just not enough engine.

11-14-2002, 06:15 AM	#4
71GMC_3/4T Weapons Of Construction Join Date: Apr 2000 Location: Colorado, USA Posts: 1,095	I just did mine a couple weeks ago. If you have the screws out of the drums (assuming you have them), you may need to back off the adjusters like FredT says. To do this, you will need a brake adjusting tool and a small long screwdriver. It helps to know what you are dealing with before you start, so try to take off both drums - you may get lucky with one. The other side will be a mirror image. Get a flashlight and look in the hole. You need to push the self adjuster arm away from the toothed adjuster wheel and hold it there. You then need to back off the adjuster wheel by engaging the brake adjuster and turning it with the brake adjuster tool. Try to turn the drum while you are doing this. If it gets tight, you are going the wrong direction. Either that, or try adjusting it without holding the self adjuster arm. It should turn easily only in one direction. Once you have established that, push in on the arm and go the other way. While you have the rearend apart, it is also a good idea to put new seals in the hubs and repack the bearings. Get a new diff cover gasket and change the oil too. It will thank you for it by lasting longer... Go to Napa for the gasket. Most of the Checker/Autozone type stores around here didn't know jack about 3/4 tons. If you're going to disassemble and repack the bearings, you will want to buy the nut keepers, which for some reason, Checker's had(!). If you don't have a 1 5/8 socket, you can tap the nuts loose (after bending the keepers out of the way) but use a drift punch instead of a chisel like the previous idiot did on mine. When I did mine, one drum was well grooved from the rivets and the other was still fair due to being lubricated by gear oil. They told me they were beyond turning, but I asked them to humor me by just smoothing them up and leaving the grooves. It's an old beater and I couldn't see spending another 100 a side on new drums. Rebuild or replace the brake cylinders while you're doing this. Good luck! __________________ 1971 GMC 2500, 402/TH400 4.10 Daily Driver Lafayette, CO



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