Never heard of any plates or ever saw any on GM rigs. I've been buying, dismantling and "studying" the GM trucks for the past 25 years and never heard of such a plate.
CK5
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8 lug hub differences? --PICS ADDED!!--
- Thread starter kd7kmp
- Start date
dont forget ford front parts are thicker and req diffrent stuff.
hope someone didnt mix up ford parts on you.
when you go to get shafts its gm/dodge outers and ford is a tad longer and specific to its self.
and possible someone cut down the rotor to the 1/2 ton size to fit 1/2 ton brakes so thay didnt need to grind calipers ?
hope someone didnt mix up ford parts on you.
when you go to get shafts its gm/dodge outers and ford is a tad longer and specific to its self.
and possible someone cut down the rotor to the 1/2 ton size to fit 1/2 ton brakes so thay didnt need to grind calipers ?
I have a set of backing plates off an 8 lug GM out back and they don't look exactly like yours. It's too dark to take any measurements, but the shape of the piece that has the arrow on it is different.
Yours might just be a different year. I have no idea what year mine are.
Don't worry about how the dust shields mount to the backing plates. Where the caliper mounts is the same. It is just the 3/4 ton mount the caliper farther out to clear the bigger rotors.I have a set of backing plates off an 8 lug GM out back and they don't look exactly like yours. It's too dark to take any measurements, but the shape of the piece that has the arrow on it is different.
Yours might just be a different year. I have no idea what year mine are.
Dumb question, I thought I've read that pushed the piston back in the caliper, but I didn't see again with a quick glace. How far did you push the piston in?
Ford is specific to itself because the spindle and caliper bracket only have 5 mounting holes so we already know that these are Chevy/Dodge parts and NOT Ford parts.
Same here, I have never seen two different diameter Chev 8lug rotors. The only difference I have noticed are some have recessed holes for the wheel studs and some dont.
Can you post more pictures of the bearing hubs? Anyone know the rotor diameter of a 1978ish Ford 44 front?
bronc3buster842001
1/2 ton status
Could they possibly be off a Jeep. Jeeps used the same spindle bolt pattern.
I think I might have found the answer. I'm looking in my brake catalog and here is what I found.
K10 1971-1986 uses rotor part number 5522 (11 7/8" diameter) and has a rotor height of 2 5/16" (rotor height is measured from the surface that mates to the hub to the rear pad side of rotor)
K20 1971-1986 uses rotor part number 5523 (12 1/2" diameter) and has a rotor height of 2 13/16".
This leads me to believe that the OP has brake brackets for a 6 lug and NOT an 8 lug and is probably why the person who sold him the axle/parts did not have them installed on the axle when he bought it.
K10 1971-1986 uses rotor part number 5522 (11 7/8" diameter) and has a rotor height of 2 5/16" (rotor height is measured from the surface that mates to the hub to the rear pad side of rotor)
K20 1971-1986 uses rotor part number 5523 (12 1/2" diameter) and has a rotor height of 2 13/16".
This leads me to believe that the OP has brake brackets for a 6 lug and NOT an 8 lug and is probably why the person who sold him the axle/parts did not have them installed on the axle when he bought it.
HOLY CRAP!!! Why didn't I see this in the first place?!?!?!
Those are 1/2 TON BACKING PLATES!!!!!!!!!
See that little tab thing where the arrow is? A true 3/4 ton plate doesn't have that!!!! I have some 3/4 ton plates for the '81 to '91 trucks and they are entirely different than the 1/2 tons!
Those are 1/2 TON BACKING PLATES!!!!!!!!!
See that little tab thing where the arrow is? A true 3/4 ton plate doesn't have that!!!! I have some 3/4 ton plates for the '81 to '91 trucks and they are entirely different than the 1/2 tons!
Ok, don't freak out. I just went back up and realized the pic was from driney.
I will get a pic of my plates for those to view. They are very visually different though.
I will get a pic of my plates for those to view. They are very visually different though.
That is the pic kd7kmp posted of his backing plate. I just added the text to point out where his differs from what I have. I don't have any 1/2 ton backing plates that are not still on a vehicle to compare with, so you may be right.
72 K20
Registered Member
I have two 8-lug and one 6-lug 10 bolts im working on right now. Let me know if you guys want me to check some measurements for you. The 8-lugs are torn apart and I could tear the 6-lug down to check it all side by side.
Ok, didn't realize it was his pic.
And yep, thats the problem right there: that plate in the pic is for a 1/2 ton, not 3/4 ton.
I'm on lunch right now and will get pics of my 3/4 ton plates after work. You guys will see the big difference immediately.
kd7kmp
Registered Member
A pic really is worth a thousand words. I have been thinking that the backing plates were wrong. If you can still post the pics, i would appreciate it. Thanks.
Kevin
Kevin
Well is there some reason you want the smaller diameter rotor? If not, those aren't the parts you want to use, so who cares how/why they don't fit.
I don't know what parts you have there (maybe a standard 1/2-ton backing plate and a Dodge rotor?), but the weirdness is enough reason not to use them. It's better if regular Chevy 3/4-ton stuff from the parts store fits when you need a new rotor or caliper. Is there even enough area on that rotor to take the whole Chevy brake pad? It's possible that backing plate and rotor go together but you need a different caliper.
I don't know what parts you have there (maybe a standard 1/2-ton backing plate and a Dodge rotor?), but the weirdness is enough reason not to use them. It's better if regular Chevy 3/4-ton stuff from the parts store fits when you need a new rotor or caliper. Is there even enough area on that rotor to take the whole Chevy brake pad? It's possible that backing plate and rotor go together but you need a different caliper.
Ok, got a pic. This plate is from the '81 to '91 K/V20/2500 series trucks. They are still interchangable with the older axles, too.
GM uses 6 different caliper mount plates. 3 for the 1/2 tons and 3 for the 3/4 tons. Of course, the 3/4 tons are slightly larger in diameter than the 1/2 tons but the 3 are different in shapes. And all are interchangable, again, with others as long as the proper 6 or 8 lug rotors are used in conjunction to the plates.
The plate years go like this:
(Not sure what year the disc brakes started 'cuz I've never messed with the '67 to '72 rigs, but whatever year they did start, was it '70 or '71?)
'71 up to '76. These are a bit smaller than the '81-'91 plates but almost identical in shape.
'77 up to '80. These are the full round, 1/4" thick plates, heavier than the others.
'81 up to '91. These are a bit bigger than the '71-'76 plates and the visible differences between the 1/2 and 3/4 tons are the little lip protruding on the 1/2 ton and the 3/4 ton has a rounder shape thats curved up slightly.
Both the '71-'76 and '81-'91 plates have the thin dust sheild spot welded on them. The '77-'80 plates are a solid round thick steel type. These are the beefiest of all.
The plate years go like this:
(Not sure what year the disc brakes started 'cuz I've never messed with the '67 to '72 rigs, but whatever year they did start, was it '70 or '71?)
'71 up to '76. These are a bit smaller than the '81-'91 plates but almost identical in shape.
'77 up to '80. These are the full round, 1/4" thick plates, heavier than the others.
'81 up to '91. These are a bit bigger than the '71-'76 plates and the visible differences between the 1/2 and 3/4 tons are the little lip protruding on the 1/2 ton and the 3/4 ton has a rounder shape thats curved up slightly.
Both the '71-'76 and '81-'91 plates have the thin dust sheild spot welded on them. The '77-'80 plates are a solid round thick steel type. These are the beefiest of all.
Geez! No replies since I made the last post yesterday. Did anyone get this problem resolved? Curious here.
79rustyk10
3/4 ton status
the backing plates on my axle are the full round 1/4" ones.
kd7kmp
Registered Member
Sorry about not updating...school has been keeping me busy the last two days (i just started grad school). I was hoping to get to the salvage yard this afternoon (they're not open on Monday), but I couldn't get away from school in time. I am headed to the salvage yard tomorrow to get the backing plates and take a closer look at the spindles as well. I will let you all know.
The brake rotors on the hubs that came with the new axle have been turned down at some point. When I looked more closely at them I could see that the vents go right to the edge of the rotor surface. Also, the height of the rotors is 2 13/16...so they are the correct rotors, just modified.
BTW, you guys have been great. I can't thank you enough for your help.
Kevin
The brake rotors on the hubs that came with the new axle have been turned down at some point. When I looked more closely at them I could see that the vents go right to the edge of the rotor surface. Also, the height of the rotors is 2 13/16...so they are the correct rotors, just modified.
BTW, you guys have been great. I can't thank you enough for your help.
Kevin
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