What size ring gear is the Eaton? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

72C203503ONTHETREE · 04-18-2004, 01:11 AM

I have just bought a 72 Custom 20 Chevy and it has the Eaton rear axle. It is a three speed and has the original 350, I trhink the whole truck is original actually. I found out what rear I had from reading on here but no one has mentioned the ring gear size. What size is it? Was there sucj a thing as posi in an Eaton in 72? Thanks for the help in advance.

Duallie · 04-18-2004, 02:28 PM

If I remember correctly, the ring gear is a hair over 10", and no Positractions were ever available. However, some did come with a Detroit Locker, the sturdiest of lockers, but it doesn't have clutches, so its not a posi.

69k5 · 04-18-2004, 04:03 PM

10.5

and if it has a no spin, there will be a sticker in the door or glove box. if theres not you can open it up and check jic.

awesome rearend. gears are gonna be 4.10 4.56 or 5.13 you can get special order 3.90 but thats it, probably
4.56

69k5

72C203503ONTHETREE · 04-18-2004, 05:51 PM

Cool, thanks, I was hoping it was a larger ring gear. I still have the sticker in the glove box with all the codes so I will have to read them closely and see what ratio I have and if theres a locker option in it. From the way it runs on the highway, I bet its the 4.10 since it doesnt scream at 60 mph. At least now I won't have to worry so much about breaking the rear end when I build up the engine. I hope the trans will hold out well also.

krue · 04-18-2004, 06:24 PM

Welcome to the board from South Mississippi. Where is Grant?

**Palf70Step** · 04-18-2004, 06:37 PM

Yeah what Krue said! Can't place Grant.

Welcome to the board.

72C203503ONTHETREE · 04-18-2004, 06:50 PM

Its about 35 miles east/se of Huntsville and about 20 miles north of Guntersville. I am on top of the mountain.

Vince M · 04-19-2004, 10:59 PM

Ring gear is 10.125 on the Eaton. It is 10.5 on the later 14 bolt rear ends.

1969 GMC · 04-20-2004, 01:16 AM

i have heard all different kinds of measurements for the Eaton ring gear, so tonight I popped the diff cover on the one sitting in my garage, that is gonna go into my GMC, to see what it was... measures 10.5" for me.

72C203503ONTHETREE · 04-20-2004, 12:56 PM

What year eaton is it? Maybe the newer ones have the 10.5. Mines a 72 so maybe it has the bigger ring gear. I will have to drain the rear in mine to change the fluid and will take the cover off since it is leaking and I want to seal it up anyway. Maybe I will be lucky and a Detroit locker will be in there to.

1969 GMC · 04-20-2004, 05:03 PM

i am not sure about the different year/different size idea, as the HO52 I have is from a '66 C/20. At least, that is what the p/o and his dad told me. I trust them, they seemed to be very knowledgeable on GM stuff.

it is from a 2wd, so I have to hack off the track bar mount and coil perches, and fab up some spring mounts for it.

i do know for a fact that its a locker, i popped the diff cover to check. also, if i spin the pinion, the hubs spin. here is a pic that shows a detroit locker inside the diff (its the little brass thing inside the ring gear):

04-18-2004, 01:11 AM	#1
72C203503ONTHETREE Registered User Join Date: Apr 2004 Location: Grant, Alabama Posts: 504	What size ring gear is the Eaton? I have just bought a 72 Custom 20 Chevy and it has the Eaton rear axle. It is a three speed and has the original 350, I trhink the whole truck is original actually. I found out what rear I had from reading on here but no one has mentioned the ring gear size. What size is it? Was there sucj a thing as posi in an Eaton in 72? Thanks for the help in advance. __________________ 72 Chevy C20, SOLD (Dang it.) 09 Challanger RT six speed in all black. 74 Datsun 710 wagon, all 1.8 liters of screaming Datsun power. 73 C10 long bed, 350/350 combo, nice shape.

04-18-2004, 02:28 PM	#2
Duallie Registered User Join Date: Feb 2001 Location: Nikiski, Alaska Posts: 477	If I remember correctly, the ring gear is a hair over 10", and no Positractions were ever available. However, some did come with a Detroit Locker, the sturdiest of lockers, but it doesn't have clutches, so its not a posi. __________________ Just as if I knew what I was doin'

04-18-2004, 05:51 PM	#4
72C203503ONTHETREE Registered User Join Date: Apr 2004 Location: Grant, Alabama Posts: 504	Cool, thanks, I was hoping it was a larger ring gear. I still have the sticker in the glove box with all the codes so I will have to read them closely and see what ratio I have and if theres a locker option in it. From the way it runs on the highway, I bet its the 4.10 since it doesnt scream at 60 mph. At least now I won't have to worry so much about breaking the rear end when I build up the engine. I hope the trans will hold out well also. __________________ 72 Chevy C20, SOLD (Dang it.) 09 Challanger RT six speed in all black. 74 Datsun 710 wagon, all 1.8 liters of screaming Datsun power. 73 C10 long bed, 350/350 combo, nice shape.

04-18-2004, 06:24 PM	#5
krue Designated A-hole! Join Date: Mar 2003 Location: South Mississippi Posts: 36,450	Welcome to the board from South Mississippi. Where is Grant? __________________ "If it ain't broke, fix it 'til it is!" Being stupid ain't illegal. We're Still Debt Free Except for the House!!! www.daveramsey.com 70 GMC SWB Stepside project "Green Booger" soon to be 6.0l/4l80e 93 S-10 "Poppaw's Truck"

04-18-2004, 06:37 PM	#6
Palf70Step State of Confusion! Join Date: Jul 2002 Location: Gulfport, MS USA Posts: 46,818	Yeah what Krue said! Can't place Grant. Welcome to the board. __________________ Bill 1970 Chevy Custom/10 LWB Fleetside 2010 Toyota Tacoma PreRunner SR5 Double Cab - DD Member of Louisiana Classic Truck Club (LCTC) Bill's Gallery Life isn't tied with a bow, but it's still a gift. Live simply. Love generously. Care deeply. Speak kindly. Leave the rest to God!

04-18-2004, 04:03 PM	#3
69k5 Registered User Join Date: Nov 2003 Location: Monroe, La 71202 Posts: 317	10.5 and if it has a no spin, there will be a sticker in the door or glove box. if theres not you can open it up and check jic. awesome rearend. gears are gonna be 4.10 4.56 or 5.13 you can get special order 3.90 but thats it, probably 4.56 69k5

04-18-2004, 06:50 PM	#7
72C203503ONTHETREE Registered User Join Date: Apr 2004 Location: Grant, Alabama Posts: 504	Its about 35 miles east/se of Huntsville and about 20 miles north of Guntersville. I am on top of the mountain. __________________ 72 Chevy C20, SOLD (Dang it.) 09 Challanger RT six speed in all black. 74 Datsun 710 wagon, all 1.8 liters of screaming Datsun power. 73 C10 long bed, 350/350 combo, nice shape.

04-19-2004, 10:59 PM	#8
Vince M Senior Member Join Date: Apr 2000 Location: Orlando, FL Posts: 1,076	Ring gear is 10.125 on the Eaton. It is 10.5 on the later 14 bolt rear ends. __________________ ............................................................ 68 Chevy CST SWB w/LS1, carb & 700r4. Golden Anniversary clone with a few improvements.

04-20-2004, 01:16 AM	#9
1969 GMC Registered User Join Date: Feb 2003 Location: The Rubber City Posts: 5,498	i have heard all different kinds of measurements for the Eaton ring gear, so tonight I popped the diff cover on the one sitting in my garage, that is gonna go into my GMC, to see what it was... measures 10.5" for me. __________________ 1969 GMC K2500 1996 Honda Accord 2007 Kawasaki KLR 650

04-20-2004, 12:56 PM	#10
72C203503ONTHETREE Registered User Join Date: Apr 2004 Location: Grant, Alabama Posts: 504	What year eaton is it? Maybe the newer ones have the 10.5. Mines a 72 so maybe it has the bigger ring gear. I will have to drain the rear in mine to change the fluid and will take the cover off since it is leaking and I want to seal it up anyway. Maybe I will be lucky and a Detroit locker will be in there to. __________________ 72 Chevy C20, SOLD (Dang it.) 09 Challanger RT six speed in all black. 74 Datsun 710 wagon, all 1.8 liters of screaming Datsun power. 73 C10 long bed, 350/350 combo, nice shape.

04-20-2004, 05:03 PM	#11
1969 GMC Registered User Join Date: Feb 2003 Location: The Rubber City Posts: 5,498	i am not sure about the different year/different size idea, as the HO52 I have is from a '66 C/20. At least, that is what the p/o and his dad told me. I trust them, they seemed to be very knowledgeable on GM stuff. it is from a 2wd, so I have to hack off the track bar mount and coil perches, and fab up some spring mounts for it. i do know for a fact that its a locker, i popped the diff cover to check. also, if i spin the pinion, the hubs spin. here is a pic that shows a detroit locker inside the diff (its the little brass thing inside the ring gear): __________________ 1969 GMC K2500 1996 Honda Accord 2007 Kawasaki KLR 650



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