rear diff identification help (I tried...) - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Luvlegs · 09-19-2006, 08:04 AM

I've spent several hours now trying to find anything about the gear ratio on the net (and in here) to id my differential - I've attached a diagram of what I have and what I've found so far.... In the near future, I will be pulling the cover, looking at the gears, changing the fluid, etc. but would like to know so I can start looking for what I want if this isn't it.... I know it's all original. Thank you all for the assistance.

jku72 · 09-19-2006, 08:32 AM

The rear ends are normally identified visually, such as 10 or 12 bolt, or the bigger dana 60's, HO 52 and HO 72. Since you have a half ton, it is either a 10 or 12 bolt. I believe a 10 bolt has a round rear cover, and a 12 bolt has a not round shaped cover.
A photo would make ID a snap.

Luvlegs · 09-19-2006, 08:41 AM

Sorry - it's a 12 bolt, I was looking for the gear ratio - thanks

jku72 · 09-19-2006, 09:11 AM

Two places to find gear ratio are the glovebox door sticker, or pop the cover and rear the stamping on the ring gear.
The other way to determine is to jack up the rear end, and put a mark on the driveshaft, turn the wheel exactly one turn, and count the number of turns the drive shaft makes. If its just under four, its a 3.73(the standard rear gears), if slightly more, its a 4.11.
There is a slim chance its a 3.07, but with a 6 cylinder, its most likely a 3.73.

Luvlegs · 09-19-2006, 09:24 AM

ok - got all that - (nothing on my glove box sticker) what I'm trying to do is verify with the numbers stamped on the axle.-
I found a bunch of sites that decipher all the numbers but most were for chevelles or camaros, etc. - no trucks.
Most only went up to 1970....and there was one that showed "RH" as a posi rear end (?).... but with only a 6 in it originally, I didn't think that sounded right.
From all the posts I've looked at, Solver seemed to be the guy with the breaks downs of the RPOs(?)...

Livrat · 09-19-2006, 09:59 AM

That is a 3:73 ratio...
Here is a link for you
http://www.americanclassic.com/paint.htm?p1=axles

Luvlegs · 09-19-2006, 11:20 AM

Thanks man - now all I need to do is figure out if it's posi or not -
What I'd really like to do is find a place for a break down of all the stampings -I know as it shows in my sketch, it was produced Oct 21, 1971... on the day shift.... kind of interesting to know - Thanks jku and livrat!

Fred T · 09-19-2006, 11:44 AM

To check for posi, jack both rear wheels and turn the right wheel. If the left wheel turns the same direction, you have posi. Also, don't trust the markings for the gear ratio. Someone before you could have swapped out the gears. Verify either by turning the wheels and counting the revs or popping the cover and looing for the ratio (or counting the gear teeth)

Luvlegs · 09-19-2006, 12:14 PM

gotcha again....on the wheel spinning and popping the cover, etc. - (I know the trucks all original - I know both POs)

Let's say I was doing a completely authentic restoration and wanted to make all the stuff match up and get all the stampings information - any idea of online sources for info? Guess I could try a dealer....

70rs/ss · 09-19-2006, 02:54 PM

Quote:

Originally Posted by Fred T

To check for posi, jack both rear wheels and turn the right wheel. If the left wheel turns the same direction, you have posi.

Fred, I know you know your stuff, but I have a posi in my camaro and my tahoe and the wheels spin in oposite directions cause they are limited slip and they only engage when one begins to loose traction. As for wondering what the gear ratio is or if it is a posi, just take the cover off. That is the only way you will know for sure, and the best we can do is speculate, if you want to know, then pull the cover and be done with it.

Longhorn Man · 09-19-2006, 03:08 PM

well if you know it is original, and the glove box sticker says nothing about posi, limited slip or something to that effect, then it isn't.

Solver · 09-19-2006, 03:17 PM

rhc is listed as: CS-CE 10, PS-PE 10 with 3:73 ratio no posi
rhx is 3:73 with Posi

Luvlegs · 09-19-2006, 04:18 PM

Thanks to all.

09-19-2006, 08:04 AM	#1
Luvlegs Registered User Join Date: Sep 2005 Location: Smith Mountain Lake Virginia Posts: 1,537	rear diff identification help (I tried...) I've spent several hours now trying to find anything about the gear ratio on the net (and in here) to id my differential - I've attached a diagram of what I have and what I've found so far.... In the near future, I will be pulling the cover, looking at the gears, changing the fluid, etc. but would like to know so I can start looking for what I want if this isn't it.... I know it's all original. Thank you all for the assistance. Attached Images __________________ "A cat will almost always blink when hit between the eyes with a ball peen hammer" (you don't always have to state the obvious) Wear your PPE! You can eat with false teeth but you can't see with a false eye. 1959 Studebaker Silverhawk 350/400 1972 C10 L6 3OTT 2005 F350 - Built - whew! Last edited by Luvlegs; 09-19-2006 at 08:42 AM.

09-19-2006, 08:32 AM	#2
jku72 Registered User Join Date: Jan 2002 Location: cornville, maine Posts: 659	Re: rear diff identification help (I tried...) The rear ends are normally identified visually, such as 10 or 12 bolt, or the bigger dana 60's, HO 52 and HO 72. Since you have a half ton, it is either a 10 or 12 bolt. I believe a 10 bolt has a round rear cover, and a 12 bolt has a not round shaped cover. A photo would make ID a snap. __________________ jku Cornville, Maine 68 C10 burb 42 Willys MB 46 Dodge WF-32 1.5 ton 53 & 56 Olds' 60 Cadillac 22 Dodge Brothers

09-19-2006, 08:41 AM	#3
Luvlegs Registered User Join Date: Sep 2005 Location: Smith Mountain Lake Virginia Posts: 1,537	Re: rear diff identification help (I tried...) Sorry - it's a 12 bolt, I was looking for the gear ratio - thanks __________________ "A cat will almost always blink when hit between the eyes with a ball peen hammer" (you don't always have to state the obvious) Wear your PPE! You can eat with false teeth but you can't see with a false eye. 1959 Studebaker Silverhawk 350/400 1972 C10 L6 3OTT 2005 F350 - Built - whew!

09-19-2006, 09:11 AM	#4
jku72 Registered User Join Date: Jan 2002 Location: cornville, maine Posts: 659	Re: rear diff identification help (I tried...) Two places to find gear ratio are the glovebox door sticker, or pop the cover and rear the stamping on the ring gear. The other way to determine is to jack up the rear end, and put a mark on the driveshaft, turn the wheel exactly one turn, and count the number of turns the drive shaft makes. If its just under four, its a 3.73(the standard rear gears), if slightly more, its a 4.11. There is a slim chance its a 3.07, but with a 6 cylinder, its most likely a 3.73. __________________ jku Cornville, Maine 68 C10 burb 42 Willys MB 46 Dodge WF-32 1.5 ton 53 & 56 Olds' 60 Cadillac 22 Dodge Brothers

09-19-2006, 09:24 AM	#5
Luvlegs Registered User Join Date: Sep 2005 Location: Smith Mountain Lake Virginia Posts: 1,537	Re: rear diff identification help (I tried...) ok - got all that - (nothing on my glove box sticker) what I'm trying to do is verify with the numbers stamped on the axle.- I found a bunch of sites that decipher all the numbers but most were for chevelles or camaros, etc. - no trucks. Most only went up to 1970....and there was one that showed "RH" as a posi rear end (?).... but with only a 6 in it originally, I didn't think that sounded right. From all the posts I've looked at, Solver seemed to be the guy with the breaks downs of the RPOs(?)... __________________ "A cat will almost always blink when hit between the eyes with a ball peen hammer" (you don't always have to state the obvious) Wear your PPE! You can eat with false teeth but you can't see with a false eye. 1959 Studebaker Silverhawk 350/400 1972 C10 L6 3OTT 2005 F350 - Built - whew! Last edited by Luvlegs; 09-19-2006 at 09:25 AM.

09-19-2006, 09:59 AM	#6
Livrat Member #1049 Join Date: Jun 2000 Location: Troy Montana Posts: 3,940	Re: rear diff identification help (I tried...) That is a 3:73 ratio... Here is a link for you http://www.americanclassic.com/paint.htm?p1=axles

09-19-2006, 11:20 AM	#7
Luvlegs Registered User Join Date: Sep 2005 Location: Smith Mountain Lake Virginia Posts: 1,537	Re: rear diff identification help (I tried...) Thanks man - now all I need to do is figure out if it's posi or not - What I'd really like to do is find a place for a break down of all the stampings -I know as it shows in my sketch, it was produced Oct 21, 1971... on the day shift.... kind of interesting to know - Thanks jku and livrat! __________________ "A cat will almost always blink when hit between the eyes with a ball peen hammer" (you don't always have to state the obvious) Wear your PPE! You can eat with false teeth but you can't see with a false eye. 1959 Studebaker Silverhawk 350/400 1972 C10 L6 3OTT 2005 F350 - Built - whew!

09-19-2006, 11:44 AM	#8
Fred T Cantankerous Geezer Join Date: Aug 2002 Location: Bel Aire, KS Posts: 6,264	Re: rear diff identification help (I tried...) To check for posi, jack both rear wheels and turn the right wheel. If the left wheel turns the same direction, you have posi. Also, don't trust the markings for the gear ratio. Someone before you could have swapped out the gears. Verify either by turning the wheels and counting the revs or popping the cover and looing for the ratio (or counting the gear teeth) __________________ Fred There is no such thing as too much cam...just not enough engine.

09-19-2006, 12:14 PM	#9
Luvlegs Registered User Join Date: Sep 2005 Location: Smith Mountain Lake Virginia Posts: 1,537	Re: rear diff identification help (I tried...) gotcha again....on the wheel spinning and popping the cover, etc. - (I know the trucks all original - I know both POs) Let's say I was doing a completely authentic restoration and wanted to make all the stuff match up and get all the stampings information - any idea of online sources for info? Guess I could try a dealer.... __________________ "A cat will almost always blink when hit between the eyes with a ball peen hammer" (you don't always have to state the obvious) Wear your PPE! You can eat with false teeth but you can't see with a false eye. 1959 Studebaker Silverhawk 350/400 1972 C10 L6 3OTT 2005 F350 - Built - whew!

09-19-2006, 03:08 PM	#11
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,693	Re: rear diff identification help (I tried...) well if you know it is original, and the glove box sticker says nothing about posi, limited slip or something to that effect, then it isn't.

09-19-2006, 03:17 PM	#12
Solver Registered User Join Date: May 2000 Location: Storm Lake, Ia Posts: 1,449	Re: rear diff identification help (I tried...) rhc is listed as: CS-CE 10, PS-PE 10 with 3:73 ratio no posi rhx is 3:73 with Posi __________________ 1972 Cheyenne Super 20 LWB-Blue 1972 Cheyenne Super 10 LWB-Black 1972 Cheyenne Super 10 LWB-Red 1972 Cheyenne Super 10 LWB-green 1972 GMC 4x4 LWB-White 1971 Cheyenne 10 LWB-Ochre 1971 Cheyenne 20 Longhorn-Copper 1971 Cheyenne 20 Longhorn-Black 1969 Custom 10 LWB-lt blue 1968 GMC 3/4 ton-green 1968 1/2 ton swb stepside-silver 1967 Chevrolet CST 10 LWB-green 1967 Chevrolet custom 20 LWB-Maroon

09-19-2006, 04:18 PM	#13
Luvlegs Registered User Join Date: Sep 2005 Location: Smith Mountain Lake Virginia Posts: 1,537	Re: rear diff identification help (I tried...) Thanks to all. __________________ "A cat will almost always blink when hit between the eyes with a ball peen hammer" (you don't always have to state the obvious) Wear your PPE! You can eat with false teeth but you can't see with a false eye. 1959 Studebaker Silverhawk 350/400 1972 C10 L6 3OTT 2005 F350 - Built - whew!



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