G80 differential - The 1947 - Present Chevrolet & GMC Truck Message Board Network

jetfixr · 03-11-2005, 11:10 AM

I have replaced the motor, tranny, and driveline in my 70 C-10, trying to upgrade things as I go. The only thing that remains of the original drivetrain is the rear-end. The glove-box sticker says it is a G80 positrac axle, does anyone know anything about this rear-end? Did they come in any particular ratio? Are they a solid rear-end? If so I will just keep it in place unless it gives me any trouble.

68c10owner · 03-11-2005, 12:55 PM

it should be a 12 bolt posi. G80 is just the GM code for it. They are strong enough and could have several different ratios. It might say on your glove box sticker what ratio it should be if it`s the original rearend.

**Already Gone** · 03-11-2005, 11:52 PM

If you have the GU4 Code its a 3:08 , GU5- 3:23, GU6-3:42, .. I wrecked an 85 Burb and it had the GT4 code which stated it was a 3:73... Hope I helped..

Longhorn Man · 03-12-2005, 12:07 AM

Where did these come from?
There was no 3.23 nor 3.42 gear sets avalible 67 - 72.

**Already Gone** · 03-12-2005, 12:18 AM

From 80's Suburbans ,I just assumed that GM like Chrysler ( where I worked for 25 years) have used the same codes forever.

**Already Gone** · 03-12-2005, 12:22 AM

So Longhorn what you are saying is that the 67/72 Trucks came with 3:73 gears, or lower ratios? On another thread you were talking about the GM Info Packet. I got that specifically for my truck and I stil haven't found what ratio my 350/Turbo350 truck came with . I do know its a 12bolt (cause I counted them, lol) non-posi Rear end.

Tx Firefighter · 03-12-2005, 12:34 AM

3.08 is also common on V8 half ton trucks too.

Longhorn Man · 03-12-2005, 12:41 AM

in 1/2 ton 67 - 72 trucks, there was 4.11 (maybe 4.10, can never remember) 3.73 and 3.07
In most of the 3/4 ton and one tons, they were 4.11 (or 4.10...again, get them flip flopped all the time) and 4.56.

I mqay be wrong on this...but I think the big blocks (both 1/2 ton and 3/4 ton) got 3.56 gears...or something like that.

03-11-2005, 11:10 AM	#1
jetfixr Registered User Join Date: Jan 2005 Location: Central CA Posts: 86	G80 differential I have replaced the motor, tranny, and driveline in my 70 C-10, trying to upgrade things as I go. The only thing that remains of the original drivetrain is the rear-end. The glove-box sticker says it is a G80 positrac axle, does anyone know anything about this rear-end? Did they come in any particular ratio? Are they a solid rear-end? If so I will just keep it in place unless it gives me any trouble.

03-11-2005, 12:55 PM	#2
68c10owner Registered User Join Date: Oct 2003 Location: Carmichael, California Posts: 3,006	it should be a 12 bolt posi. G80 is just the GM code for it. They are strong enough and could have several different ratios. It might say on your glove box sticker what ratio it should be if it`s the original rearend. __________________ Anthony

03-11-2005, 11:52 PM	#3
Already Gone 70+ ( Old Skool Club ) Join Date: Nov 2003 Location: Saskatoon, Saskatchewan ,Canada Posts: 9,139	Ratios If you have the GU4 Code its a 3:08 , GU5- 3:23, GU6-3:42, .. I wrecked an 85 Burb and it had the GT4 code which stated it was a 3:73... Hope I helped.. __________________ 1972 C10 Custom/Deluxe 613 Highlander 406/700R4 1999 White Tahoe LS 4x2 with Z56 Police Package 1992 K1500 GMC Suburban Members I have personally met: MusicMan70 - HeavyD - ChewyChevy67 - StingRay -71SWB4x4 - 67 Burb - DeadheadNM - too much stuff - bc65 - das601 " Circumsatances Do Not Change Responsibility " " The Sky is not the Limit, Your Mind is." Marilyn Monroe .. RIP Charlie Watts 1941 - 2021

03-12-2005, 12:18 AM	#5
Already Gone 70+ ( Old Skool Club ) Join Date: Nov 2003 Location: Saskatoon, Saskatchewan ,Canada Posts: 9,139	From From 80's Suburbans ,I just assumed that GM like Chrysler ( where I worked for 25 years) have used the same codes forever. __________________ 1972 C10 Custom/Deluxe 613 Highlander 406/700R4 1999 White Tahoe LS 4x2 with Z56 Police Package 1992 K1500 GMC Suburban Members I have personally met: MusicMan70 - HeavyD - ChewyChevy67 - StingRay -71SWB4x4 - 67 Burb - DeadheadNM - too much stuff - bc65 - das601 " Circumsatances Do Not Change Responsibility " " The Sky is not the Limit, Your Mind is." Marilyn Monroe .. RIP Charlie Watts 1941 - 2021

03-12-2005, 12:22 AM	#6
Already Gone 70+ ( Old Skool Club ) Join Date: Nov 2003 Location: Saskatoon, Saskatchewan ,Canada Posts: 9,139	Mmmm!!! So Longhorn what you are saying is that the 67/72 Trucks came with 3:73 gears, or lower ratios? On another thread you were talking about the GM Info Packet. I got that specifically for my truck and I stil haven't found what ratio my 350/Turbo350 truck came with . I do know its a 12bolt (cause I counted them, lol) non-posi Rear end. __________________ 1972 C10 Custom/Deluxe 613 Highlander 406/700R4 1999 White Tahoe LS 4x2 with Z56 Police Package 1992 K1500 GMC Suburban Members I have personally met: MusicMan70 - HeavyD - ChewyChevy67 - StingRay -71SWB4x4 - 67 Burb - DeadheadNM - too much stuff - bc65 - das601 " Circumsatances Do Not Change Responsibility " " The Sky is not the Limit, Your Mind is." Marilyn Monroe .. RIP Charlie Watts 1941 - 2021

03-12-2005, 12:07 AM	#4
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,693	Where did these come from? There was no 3.23 nor 3.42 gear sets avalible 67 - 72.

03-12-2005, 12:34 AM	#7
Tx Firefighter Watch out for your cornhole ! Join Date: Jun 2003 Location: Azle, Texas Posts: 14,162	3.08 is also common on V8 half ton trucks too. __________________ I'm on the Instagram- @Gearhead_Kevin

03-12-2005, 12:41 AM	#8
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,693	in 1/2 ton 67 - 72 trucks, there was 4.11 (maybe 4.10, can never remember) 3.73 and 3.07 In most of the 3/4 ton and one tons, they were 4.11 (or 4.10...again, get them flip flopped all the time) and 4.56. I mqay be wrong on this...but I think the big blocks (both 1/2 ton and 3/4 ton) got 3.56 gears...or something like that.



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