Dumb full floater question, drums come off?

[RT]

Okay, stupid question: Do the brake drums on the full-floater 8lug rear axle of a 93 C2500HD come off? Or are they integral with the hub? Thanks, RT

[restoguy]

Not really a dumb question if you've never had to work on a FF before! They are just like a semi or other large truck. The hub is held to the axle tube with a big spanner nut. You'll see it after you take the axle shafts out. when you back that nut off the whole thing comes off. The drum is actuall held on to the hub by the wheel studs. I use an air hammer(muffler gun) with a pointed shank. Turn the drum onto it's back side, put the shank in the middle of a stud and give'er a burp. Shouldn't take too much effort and they'll pop right out the back side. When they are all out the drum comes off the hub real easy! Be careful not to damage the threads on your studs though. I usually put them back together the same way, with the air hammer. When you put the hub back on you've got to be sure that you get the bearing pre-load right too. It's kind of hard to explain, I just know how it 'feels'. Hope you're not doing brakes and expecting to pay K1500 prices for the parts. I was the first time and almost put a brick in my pants, if you know what I mean! Now that I've had my 6.5L K2500 for a while I've gotten used to the parts prices.

[rjschoolcraft]

I finally became a believer...

You can take the drums off without removing the hub. Make sure and adjust the brakes in to clear the wear ridge. A few light smacks with a hammer and voila!

[TurboDiverArt]

Slide off the one-ton rears too. Suburban's slide right off without the use of a hammer.

Art.

[ANXIOUS-SUBMAN]

I had to use a smoke wrench (maybe 30seconds or minute)to expand the hole in the drum where it fits over the hub. Then smacked the hub with a hammer a couple times and they came right off.

[JoeyD]

Only the sub have slide off drums for some reason.

[ees]

I think it depends on how long they have been on as to sliding them off while the hub is still on the truck. There is no way mine would have. I took the hub and drum off as a unit. I placed the drum on a cement floor with the wheel studs pointing up. I put a 4x4 block of wood on top of the hub and had at it with a sledge hammer. For one of them it took just one hit. The other took three. The hubs just dropped out at that point.

I had a great deal of trouble getting the correct replacement units. Take your old ones with you to the parts store so you can double check.

[JoeyD]

Burbs use a drum that slides on without taking the hub apart. I have no clue why they uses it on the burb and not the pick ups.

[TurboDiverArt]

Originally posted by Joey D:
Burbs use a drum that slides on without taking the hub apart. I have no clue why they uses it on the burb and not the pick ups. I believe the Subs have 1-ton rears to compensate for the heavier chassis vs. a pickup with

[JoeyD]

My 96 3500 did not have the slide on drums, same with my 2500. The 2500 has the 2.5 in shoe and the 3500 had the 3.5 in shoe. The burb with the ff axle has the 3.5 in shoe. I don't see why they did what they did.

[TurboDiverArt]

Originally posted by Joey D:
My 96 3500 did not have the slide on drums, same with my 2500. The 2500 has the 2.5 in shoe and the 3500 had the 3.5 in shoe. The burb with the ff axle has the 3.5 in shoe. I don't see why they did what they did. Huh, I thought I read the 3500's had slide off drums and 1-ton rears like the burbs. My burb does have 3.5" drums as you state. Trying to apply logic to the GM engineers and figure out what they were thinking will drive you nuts. Just like asking yourself why they never intercooled the turbo diesel engines....

Art.

[DmaxMaverick]

When talking about 2500's, it is important to know which one. The 2500LD has a GVWR of 7200#, and a semi-floater r/e. The 2500HD has a GVWR of 8600#, and a full-floater, same as the 3500SRW. The Sub's will track the higher capacities of their respective ratings. GVWR's determine the powertrain components, not the class designations. A fine example of this was the 1500HD. Although it was badged a 1500 (1/2 ton), it sported the same powertrain as the 2500, with a GVWR of 8600#. Brake shoe size is also relative to the GVWR.

Also, just because the drum doesn't slide off doesn't mean it isn't supposed to. Time, use, and elements will cause them to seize onto the hub and studs. Machining variations can play a part, also. Some fit very tight, while others fall off when the wheel is removed.

[rjschoolcraft]

No. The 2500 HD trucks (pre-2001) with 8600 GVW (that I've seen) did not have full-floater diffs. They had the 9.5" ring gear with C-clips. The 3500 SRW's had the 10.5" 14 bolt as did the 2500 HD subs. The 7200 GVW trucks had an 8.5" ring gear with C-clips.

[restoguy]

My '94 K2500(8600GVW) 6.5L TD has a full float 10.5" and my friend's '96 was the same way. I know another guy locally that has an 8600GVW truck that has a semi-floater 9.5". I figured that his must be a lower GVW, but I personally checked it and it wasn't. It is a small block gasser though. Don't know what else the rhyme or reason is. The newer trux have an 11.5" ring according to Randy's Ring and Pinion. As for my drums, there's no way the would have slid off. The studs had 'splines' to keep them stuck in place. Those 'splines' went thourgh the hub into the drum and held it tight.

[CareyWeber]

Originally posted by ronniejoe:
No. The 2500 HD trucks (pre-2001) with 8600 GVW (that I've seen) did not have full-floater diffs. They had the 9.5" ring gear with C-clips. The 3500 SRW's had the 10.5" 14 bolt as did the 2500 HD subs. The 7200 GVW trucks had an 8.5" ring gear with C-clips. Ron,

I think this what determines if a pre HD 2500 with 8600 lb GVW has a full floater or a SF 14 bolt axle is:

Gas small blocks = SF axle 9.5 (V-6 too)
Gas big block = FF axle 10.5

Diesel 6.2 = SF axle 9.5
Diesel 6.5TD = FF axle 10.5

Carey

[moondoggie]

Good Day!

My 95 pickup says "2500" on the side. The tag says 8600 GVWR. It has a 14-bolt full-floating 4.10 ratio rear axle; unfortunately, I have no idea what diameter the ring gear is. (Where do you measure this diameter, anyway? If/when I have the covers off my trucks, I'd like to measure them.) This has the rear brakes that we

[DmaxMaverick]

I hadn't considered entering the SB gasser (or the 6.2L, for that matter) into the argument, as we are talking about 6.5TD equipped trucks.

As well as the GVWR, GCWR is also entered into the formula for the powertrain. Once again, the engine isn't the deciding factor. A formula is used to determine the powertrain components. GVWR, GCWR, are essentially the cause (or the result) of the component inclusions. The SB gasser was also used on the 3500's, and it has a full floater.

The axle manufacturers determine the capacity of their axle, and GM (or any mfg) sets the vehicle's axle rating according to their requirements. A good example of this is the current AAM 11.5 axle, used on the 2001+ 2500HD and 3500. It is rated by AAM at 10,400# GAWR, but the 2500HD's axle is rated at 6084#. Incidentally, this happens to be the exact combined capacity of the go-cart tires GM equips on the truck (3042 X 2).

[ace58]

The 1500 diesel suburbans (8050 GVW) have semi floating rear ends, similar to the gas but still a 14 bolt, and I had a swell time getting even that style off. I moved the adjuster all the way in and it had frozen to the face of the axle.

Rear discs would have been nice innovation back then.

[Andy Chesek]

My last truck:

'97 Chevy K2500
8600 GVWR
5.7L small block
NV4500 manual tranny
14 bolt FF rear axle (10.5" ring gear)
13" drums on the rear


The smaller 14 bolt SF axle will have 11" drums.


Carey is probably pretty close with his post, but I'd add that trucks with small block engines and manual transmissions probably got the beefier rear axle. I know for a while, Dodge put Dana 70 rears behind their automatic/Cummins-equipped trucks, and threw the Dana 80 in the back of manual/Cummins trucks.