What Size Brakes On The Rear?

Rogue Leader · October 24, 2011

So I'm trying to diagnose my rear brake issue. Basically the ABS seems to activate when I stop (just the last few feet at about 2 mph) and I believe on these trucks (96 GMC 2500) it was rear only correct? It also pulls to the right when this happens.

Ive resolved to just replacing everything but I'm kinda confused, I would assume my truck has the 13 inch rear drums but it mentions both a 2.5 and 2.75" brake shoe (Some sites even say 3"!). Without taking it apart is there an option that would tell me which I have? Its got the tow package, 14 bolt, 8 lug, 4.10, G80 option code.

govtech · October 25, 2011

aftermarket catalogs suck....just take it apart and measure the drum and shoes width,,takes 2 minutes

no guessing

Rogue Leader · October 25, 2011

aftermarket catalogs suck....just take it apart and measure the drum and shoes width,,takes 2 minutes

no guessing

I'd love to except I'm pressed for time and the wheels are rusted on to the drums. I'd like to order everything I need so that when I take it apart I can toss all the old crap in the trash and replace it all in 1 shot.

I'm tending to assume the 3 inch brakes are what I need due to the towing package option code on the truck....

grampadirt · October 25, 2011

I have that same axle under my '95 K2500 Burb and recently did the rear brakes.The drum is 13'' and the shoes are 2 3/4''(still have the old ones and just measured them).There was a four wheel ABS option available also(which my Burb has).

It's a full floater,right?

Rogue Leader · October 25, 2011

I have that same axle under my '95 K2500 Burb and recently did the rear brakes.The drum is 13'' and the shoes are 2 3/4''(still have the old ones and just measured them).There was a four wheel ABS option available also(which my Burb has).

It's a full floater,right?

Cool thanks for your help. I guess it would be a full floater. Just got the truck a week ago and I'm mainly a car guy.

Regarding the ABS the fact it pulls to the right when the ABS activates makes me tend to believe maybe it is 4 wheel. Do you happen to know what the option code was for that?

grampadirt · October 25, 2011

I have that same axle under my '95 K2500 Burb and recently did the rear brakes.The drum is 13'' and the shoes are 2 3/4''(still have the old ones and just measured them).There was a four wheel ABS option available also(which my Burb has).

It's a full floater,right?

Cool thanks for your help. I guess it would be a full floater. Just got the truck a week ago and I'm mainly a car guy.

Regarding the ABS the fact it pulls to the right when the ABS activates makes me tend to believe maybe it is 4 wheel. Do you happen to know what the option code was for that?

Off hand,no.But if you go look behind the front wheels and see a wiring harness going from the frame to each wheel it's a good bet you have 4 wheel ABS.If your axle extends out past the wheel and has six(IIRC)bolts it's a full floatter and is as good as it gets

I'll fetch a pic from PB,brb........

Full floater axle:

Rogue Leader · October 25, 2011

I have that same axle under my '95 K2500 Burb and recently did the rear brakes.The drum is 13'' and the shoes are 2 3/4''(still have the old ones and just measured them).There was a four wheel ABS option available also(which my Burb has).

It's a full floater,right?

Cool thanks for your help. I guess it would be a full floater. Just got the truck a week ago and I'm mainly a car guy.

Regarding the ABS the fact it pulls to the right when the ABS activates makes me tend to believe maybe it is 4 wheel. Do you happen to know what the option code was for that?

Off hand,no.But if you go look behind the front wheels and see a wiring harness going from the frame to each wheel it's a good bet you have 4 wheel ABS.If your axle extends out past the wheel and has six(IIRC)bolts it's a full floatter and is as good as it gets

I'll fetch a pic from PB,brb........

Full floater axle:

Cool thanks for the explanation. I actually do not have the full floater setup. The end of my axle looks like one from any regular car.

I hope its not the ABS modulator that is my problem, best price I could find on one was $400

grampadirt · October 25, 2011

I have that same axle under my '95 K2500 Burb and recently did the rear brakes.The drum is 13'' and the shoes are 2 3/4''(still have the old ones and just measured them).There was a four wheel ABS option available also(which my Burb has).

It's a full floater,right?

Cool thanks for your help. I guess it would be a full floater. Just got the truck a week ago and I'm mainly a car guy.

Regarding the ABS the fact it pulls to the right when the ABS activates makes me tend to believe maybe it is 4 wheel. Do you happen to know what the option code was for that?

Off hand,no.But if you go look behind the front wheels and see a wiring harness going from the frame to each wheel it's a good bet you have 4 wheel ABS.If your axle extends out past the wheel and has six(IIRC)bolts it's a full floatter and is as good as it gets

I'll fetch a pic from PB,brb........

Full floater axle:

Cool thanks for the explanation. I actually do not have the full floater setup. The end of my axle looks like one from any regular car.

I hope its not the ABS modulator that is my problem, best price I could find on one was $400

Then you probably have a SF(semi floater)and the drums & shoes might be smaller,you might have to pull a drum,like was suggested earlier,to know for sure.I've always had FFs,don't know much about SFs.On my Burb I've replaced both front ABS sensors to get rid of the dreaded ABS light on the dash,no prob with the rear yet(knock on wood)

My ABS module seems to be working so I have no info on that except they can be rebuilt.Where? Search GMT,I know it's here somewhere...

Rogue Leader · October 25, 2011

Then you probably have a SF(semi floater)and the drums & shoes might be smaller,you might have to pull a drum,like was suggested earlier,to know for sure.I've always had FFs,don't know much about SFs.On my Burb I've replaced both front ABS sensors to get rid of the dreaded ABS light on the dash,no prob with the rear yet(knock on wood)

My ABS module seems to be working so I have no info on that except they can be rebuilt.Where? Search GMT,I know it's here somewhere...

As soon as I saw your picture I was thinking the same thing. Its probably the smaller ones but looks like I'm not getting around taking it apart, measuring, putting it back together and then buying.

I surprisingly do not get a brake or ABS warning light on my dash (and they do work as they light up on startup test), my problem is the abs continually activates whenever I am coming to a stop for the last 2 mph. I do not hear grinding on the brakes like the pads are worn out but I am hoping that is the issue and just replacing the springs/shoes in the rear and the pads in front may do the trick. I have heard that worn pads can make older ABS setups freak out. It looks like the ABS controller under the hood was replaced before (it has a marking on it "96 Tahoe" in grease pencil like from a junkyard). The brakes seem to work fine and the same as any other 2500 I've driven, except for that list ABS activation.

If I could just get the damn wheels off this would go much easier..... back to dousing them with PB blaster!

ChevyTech77 · October 25, 2011

Clean the wss mounting surfaces on the front hub bearings until the front wss's can produce 350 acmv easily when you spin the tires by hand.

Your rear brakes have nothing to do with it(abs coming on unwanted). If you have a 2500 8 lug, semi-float rear axle, you have the 13 x 2.5" rear shoes. The 2.75" wide shoes were used on srw full float applications and 3" wide shoes were used in the drw full float applications.

Rogue Leader · October 25, 2011

Clean the wss mounting surfaces on the front hub bearings until the front wss's can produce 350 acmv easily when you spin the tires by hand.

Your rear brakes have nothing to do with it(abs coming on unwanted). If you have a 2500 8 lug, semi-float rear axle, you have the 13 x 2.5" rear shoes. The 2.75" wide shoes were used on srw full float applications and 3" wide shoes were used in the drw full float applications.

GREAT info thanks I will be doing this over the weekend!

Debo511 · October 25, 2011

Clean the wss mounting surfaces on the front hub bearings until the front wss's can produce 350 acmv easily when you spin the tires by hand.

Your rear brakes have nothing to do with it(abs coming on unwanted). If you have a 2500 8 lug, semi-float rear axle, you have the 13 x 2.5" rear shoes. The 2.75" wide shoes were used on srw full float applications and 3" wide shoes were used in the drw full float applications.

What he said...

Rogue Leader · October 25, 2011

Thanks guys I'm actually gonna try to take a look at this tonight. Do I need to disassemble the front brakes to clean this or can I remove it from the back and clean it there?

ChevyTech77 · October 25, 2011

Thanks guys I'm actually gonna try to take a look at this tonight. Do I need to disassemble the front brakes to clean this or can I remove it from the back and clean it there?

Brake rotor has to come off which on this truck, isn't much fun because it is held to the hub bearing with the wheel studs. (I assume this is 4WD when saying that). Brake caliper off, axle nut off, loosen all four hub bearing bolts and then tap on each hub bearing bolt head evenly, using a hammer and a punch, to get the hub bearing/rotor out of the steering knuckle. From there, you can remove the sensor from the hub bearing and clean the mounting surface of the sensor.