Hub size difference? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Tully · 02-05-2005, 09:54 AM

I have a 72 chevy K 20 with 8 hole rims and a 4 1/2" center hole. I also have K 20 chassis (un sure of year) under a 71 GMC body it has 8 hole rims with a 4 3/4" center hole. Why the difference? The chevy has a corperate rear axle and the gmc a dana, but the front hubs are different too. Could this be clue to what year my chassis is? I know this is the place to ask to get it strait, the knowledge on this board is incredible.

ryanroo · 02-05-2005, 12:45 PM

i think the hole size could just be the wheels if the chassis is a 70-72 it should have the same hubs as long as it has an original big hub type dana 44. i know some aftermarket wheel are sold with bigger hub openings because ford truck require them, so maybe they are ford rims or aftermarket universal.
Ryan

Tully · 02-05-2005, 02:06 PM

I guess I was confusing in my question, am not asking about the wheels, I know I have several different brands of wheels. The hubs on the trucks are different, they are both Dana 44 fronts to my knowledge. I don't know the different part names of the brake drum-hub assembly but the spindle cone where the locking hub attaches is different diameter on the trucks also, much larger on the 72, but that's not where the wheels seat , where the wheels seat on the drum-hub is what is 1/4" different on the two trucks, and that is my question, sorry for the confusion.

**JIMs70GMC** · 02-05-2005, 08:16 PM

The only thing I can think of is one is an internal style hub and the other the older external style hub. Are the dana44s both open knuckle?

4x4Poet · 02-06-2005, 01:52 AM

I was thinking the same thing, Jim. Or a different type bolt on hub assy from a later year axle. Tully, you need to tell us how the manual locking hubs attach to their respective wheel bearing hubs. Bolts (allen head), internal splines, or studs with nuts, cone washers, lock tabs, etc.? Pics would be best if you have a digicam.

Tully · 02-06-2005, 09:31 AM

Yes they are both open knuckle danas. The fronts are both disc, if you knocked the rotors off the 72 the hub comes strait out 4 1/2" diameter then the lock outs are bolted on with large allen bolts. On the other one with the rotor off, where the rim seats it's 4 3/4" then it tapers down to the locking hub with small allen bolts. The rear drum/ hub asbly are the same, 72 is 4 1/2" the other 4 3/4" where the rims seat. The only difference in the drive train I can tell is the corperate (eaton) rear in the 72 and the dana in the other.

Bob Chayer · 02-06-2005, 10:25 AM

The 3/4 ton axle has larger wheel bearings than the 1/2 ton and the locking hub is externaly mounted. The 3/4 ton axle is also wider buy a couple inches or so than the 1/2 ton. The 3/4 ton is 8 lug. All the rest is the same. At least this is the way it is on my '71 3/4 ton Suburban and my '72 1/2 ton pickup.

**JIMs70GMC** · 02-06-2005, 05:51 PM

Bob, he has 2 different generation dana 44s, 3/4 ton. The one with large allen heads is the external style hub and the smaller one is an internal style hub.

Truckstuff · 02-09-2005, 12:54 PM

Here is a older (-- to 75) 3/4Ton Dana 44 External Hub. This one uses the larger center hole rim.

Tully · 02-10-2005, 10:51 PM

That's the exact hub thats on my 72 and 4 1/2" center hole rims fit on them. My other chassis has the internal bolt on hubs and they take a 4 3/4" rim. What's up with this? is it a clue to the age of this chassis? I was thinking 71 or 72 because of the disk brakes.

02-05-2005, 09:54 AM	#1
Tully Registered User Join Date: Jan 2005 Location: Hiles, WI Posts: 42	Hub size difference? I have a 72 chevy K 20 with 8 hole rims and a 4 1/2" center hole. I also have K 20 chassis (un sure of year) under a 71 GMC body it has 8 hole rims with a 4 3/4" center hole. Why the difference? The chevy has a corperate rear axle and the gmc a dana, but the front hubs are different too. Could this be clue to what year my chassis is? I know this is the place to ask to get it strait, the knowledge on this board is incredible.

02-05-2005, 12:45 PM	#2
ryanroo Senior Member Join Date: Apr 2004 Location: sw colorado Posts: 2,720	i think the hole size could just be the wheels if the chassis is a 70-72 it should have the same hubs as long as it has an original big hub type dana 44. i know some aftermarket wheel are sold with bigger hub openings because ford truck require them, so maybe they are ford rims or aftermarket universal. Ryan __________________ 72 K20 12v build 72 K20 "parts truck" A place for your diesel swap questions

02-05-2005, 08:16 PM	#4
JIMs70GMC user # 2756 Join Date: Jun 2001 Location: Chesapeake, Virginia Posts: 4,612	The only thing I can think of is one is an internal style hub and the other the older external style hub. Are the dana44s both open knuckle? __________________ 1970 K25, 8' stepside bed 350/465/205 44 up front, 60 in the rear 4.10s rolling on 33" Dunlop MTs 1986 K5, 350/465/208 Dana 60/14 bolt from a cucv 36" Super Swampers TSL/SX 1983 K20 w/ CUCV axles, 350/700R4/208 sitting on 37" Goodyears 1986 M1031 6.2 diesel, TH400/NP205 locker in the rear and a LS in the front, all stock for now..... 1986 K30, 350/400/205 dana 60 and 14 bolt. I kept the drivetrain. Body/bad and chassis are gone. 1981 K30, 350/465/205 dana 60 and dually 14 bolt. Has a G80, and a flat bed. Going to replace the flat bed. 1985 K20, 350/400/208 10 bolt and SF 14 bolt. I wonder where I can find some 1 tons. Hmmmmm Last edited by JIMs70GMC; 02-05-2005 at 08:27 PM.

02-06-2005, 01:52 AM	#5
4x4Poet Registered User Join Date: Nov 2004 Location: "Under Montana skies." Posts: 1,836	I was thinking the same thing, Jim. Or a different type bolt on hub assy from a later year axle. Tully, you need to tell us how the manual locking hubs attach to their respective wheel bearing hubs. Bolts (allen head), internal splines, or studs with nuts, cone washers, lock tabs, etc.? Pics would be best if you have a digicam. __________________ '71 GMC K20 Suburban, '71 GMC K10 Suburban, '72 Chevy C10 CST Suburban, '72 Chevy K20 clunker pickup. Last edited by 4x4Poet; 02-06-2005 at 03:39 AM.

02-06-2005, 10:25 AM	#7
Bob Chayer Registered User Join Date: Dec 2002 Location: Mid, NH Posts: 150	The 3/4 ton axle has larger wheel bearings than the 1/2 ton and the locking hub is externaly mounted. The 3/4 ton axle is also wider buy a couple inches or so than the 1/2 ton. The 3/4 ton is 8 lug. All the rest is the same. At least this is the way it is on my '71 3/4 ton Suburban and my '72 1/2 ton pickup. __________________ Bob Chayer 71 3/4 ton 4X4 Suburban

02-05-2005, 02:06 PM	#3
Tully Registered User Join Date: Jan 2005 Location: Hiles, WI Posts: 42	I guess I was confusing in my question, am not asking about the wheels, I know I have several different brands of wheels. The hubs on the trucks are different, they are both Dana 44 fronts to my knowledge. I don't know the different part names of the brake drum-hub assembly but the spindle cone where the locking hub attaches is different diameter on the trucks also, much larger on the 72, but that's not where the wheels seat , where the wheels seat on the drum-hub is what is 1/4" different on the two trucks, and that is my question, sorry for the confusion.

02-06-2005, 09:31 AM	#6
Tully Registered User Join Date: Jan 2005 Location: Hiles, WI Posts: 42	Yes they are both open knuckle danas. The fronts are both disc, if you knocked the rotors off the 72 the hub comes strait out 4 1/2" diameter then the lock outs are bolted on with large allen bolts. On the other one with the rotor off, where the rim seats it's 4 3/4" then it tapers down to the locking hub with small allen bolts. The rear drum/ hub asbly are the same, 72 is 4 1/2" the other 4 3/4" where the rims seat. The only difference in the drive train I can tell is the corperate (eaton) rear in the 72 and the dana in the other.

02-06-2005, 05:51 PM	#8
JIMs70GMC user # 2756 Join Date: Jun 2001 Location: Chesapeake, Virginia Posts: 4,612	Bob, he has 2 different generation dana 44s, 3/4 ton. The one with large allen heads is the external style hub and the smaller one is an internal style hub. __________________ 1970 K25, 8' stepside bed 350/465/205 44 up front, 60 in the rear 4.10s rolling on 33" Dunlop MTs 1986 K5, 350/465/208 Dana 60/14 bolt from a cucv 36" Super Swampers TSL/SX 1983 K20 w/ CUCV axles, 350/700R4/208 sitting on 37" Goodyears 1986 M1031 6.2 diesel, TH400/NP205 locker in the rear and a LS in the front, all stock for now..... 1986 K30, 350/400/205 dana 60 and 14 bolt. I kept the drivetrain. Body/bad and chassis are gone. 1981 K30, 350/465/205 dana 60 and dually 14 bolt. Has a G80, and a flat bed. Going to replace the flat bed. 1985 K20, 350/400/208 10 bolt and SF 14 bolt. I wonder where I can find some 1 tons. Hmmmmm

02-09-2005, 12:54 PM	#9
Truckstuff Registered User Join Date: Dec 2003 Location: Cloverdale, British Columbia Canada Posts: 159	Here is a older (-- to 75) 3/4Ton Dana 44 External Hub. This one uses the larger center hole rim. Attached Images __________________ Real Trucks are Built not Bought Building: 1981 GM SB LowRider 1985 GM K3500 3+3 1981 GM K2500 SSB 1980 GM K2500 X-BC Hydro 1979 GM K3500 3+3 1976 GM K5 Blazer 1970 Custom 10 http://bc4x4.com/ Last edited by Truckstuff; 02-09-2005 at 01:02 PM.

02-10-2005, 10:51 PM	#10
Tully Registered User Join Date: Jan 2005 Location: Hiles, WI Posts: 42	That's the exact hub thats on my 72 and 4 1/2" center hole rims fit on them. My other chassis has the internal bolt on hubs and they take a 4 3/4" rim. What's up with this? is it a clue to the age of this chassis? I was thinking 71 or 72 because of the disk brakes.

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