what rear gear in a 72 6cyl 3 on the tree? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

djracer · 08-11-2003, 08:58 AM

Also do you look for a certain option code for positive traction? Or do I need to buy an aftermarket posi.

Knoxville71shortbed · 08-11-2003, 10:12 AM

I don't know about all of them, but my '71 came stock with 3.73 gears. It has the 250 I-6, and 3-on-the-tree. Mine does not have posi-traction. As far as I can tell, my truck was built with zero options, so I would guess the 3.73 rearend was standard. I actually like the setup. The 250 has good low-end torque, and pulls strong from a standing start with the 3-speed. Of course, top speed is somewhat limited, but unless you do a lot of freeway driving, it's really not a problem. I will also add that my gas mileage isn't that great for a 6-cylinder. I probably only get around 17 or 18 mpg. But I doubt that the guys running 350s get that kind of mileage. Also, my truck is a short-fleet bed, so it probably feels spunkier with this drivetrain than a LWB would. In this truck, this drivetrain seems more than adequate, and is a blast to drive. I'm not planning on changing the rearend, or any other part of the drivetrain. However, if it had posi-traction, that would be even better.

Bill72BB · 08-11-2003, 10:44 AM

Resto manuel shows 3:73 stock , with 3:07 and 4:11 optional.

djracer · 08-11-2003, 12:42 PM

anyone know the option code for posi? I am going to the junk yard!

GM72K10 · 08-11-2003, 10:02 PM

G80 Positraction (Half tons) G86 No spin G87 Power Lock (What's in my 72 K25) Make sure that's what's actually under the truck though!

GM
GM

djracer · 08-11-2003, 10:13 PM

they still use that code on some later model stuff I know at least 99 my buddy has a 1 ton crew with a g80

Thanks
Kevin

08-11-2003, 08:58 AM	#1
djracer Registered User Join Date: Feb 2001 Location: Wetumpka, Al, U.S. Posts: 8,891	what rear gear in a 72 6cyl 3 on the tree? Also do you look for a certain option code for positive traction? Or do I need to buy an aftermarket posi. __________________ Kevin Special Thanks to All who have helped on the TRUCK! My Pass Time Show http://s129.photobucket.com/albums/p...Chapter1-0.mp4 So Far my best Times are: Motor only: 6.44 1/8 @ 104.13 10.39 1/4 @ 125.83 Nitrous Times: 5.785 1/8 @ 118.65 with a 1.336 60ft 9.168 1/4 @ 142.58 with a 250 shot dead out of the hole!

08-11-2003, 10:44 AM	#3
Bill72BB Thats the Hillbilly way Join Date: Jul 2001 Location: Torrance,Ca Posts: 5,980	Resto manuel shows 3:73 stock , with 3:07 and 4:11 optional. __________________ BILL Torrance Calif 90504 Member DUF Club Member Old Farts Club 72 3/4ton Custom Camper BB402/400 trans Dynomax Cerama-coat headers , Hei distributor ,Edelbrock 1411 air,ps,pb,leafsprings ,98 chevy 60/40 seat,S10 shoulder belts tilt,3.54 Dana 60 rear. 16" Eagle wheels with LT265/75 16 tires,Gaylord Lid,H4 headlights with 100W relay conversion. " If I knew I was going to live this long I would have taken better care of myself " Marriage changes passion...suddenly you're in bed with a relative. A GUY'S PRAYER.... Lord, I pray for a nympho with huge boobs who owns a liquor store and likes to fish and hunt and has a Harley .Amen ,

08-11-2003, 12:42 PM	#4
djracer Registered User Join Date: Feb 2001 Location: Wetumpka, Al, U.S. Posts: 8,891	anyone know the option code for posi? I am going to the junk yard! __________________ Kevin Special Thanks to All who have helped on the TRUCK! My Pass Time Show http://s129.photobucket.com/albums/p...Chapter1-0.mp4 So Far my best Times are: Motor only: 6.44 1/8 @ 104.13 10.39 1/4 @ 125.83 Nitrous Times: 5.785 1/8 @ 118.65 with a 1.336 60ft 9.168 1/4 @ 142.58 with a 250 shot dead out of the hole!

08-11-2003, 10:02 PM	#5
GM72K10 Next! Join Date: Jan 2003 Location: Eastern Pa. Posts: 2,478	G80 Positraction (Half tons) G86 No spin G87 Power Lock (What's in my 72 K25) Make sure that's what's actually under the truck though! GM GM __________________ 86 K30 CUCV M1028A1 86 K30 CUCV M1028a2 dually 86 K30 C&C 6.2 4:56s, 4M, 11,000 gvw, ex fire truck, now lowboy dump More square bodies and CUCVs than I care to admit to 2020 Silverado K3500HD Work truck

08-11-2003, 10:13 PM	#6
djracer Registered User Join Date: Feb 2001 Location: Wetumpka, Al, U.S. Posts: 8,891	they still use that code on some later model stuff I know at least 99 my buddy has a 1 ton crew with a g80 Thanks Kevin __________________ Kevin Special Thanks to All who have helped on the TRUCK! My Pass Time Show http://s129.photobucket.com/albums/p...Chapter1-0.mp4 So Far my best Times are: Motor only: 6.44 1/8 @ 104.13 10.39 1/4 @ 125.83 Nitrous Times: 5.785 1/8 @ 118.65 with a 1.336 60ft 9.168 1/4 @ 142.58 with a 250 shot dead out of the hole!

08-11-2003, 10:12 AM	#2
Knoxville71shortbed Registered User Join Date: Jan 2002 Location: Knoxville, TN, USA Posts: 56	I don't know about all of them, but my '71 came stock with 3.73 gears. It has the 250 I-6, and 3-on-the-tree. Mine does not have posi-traction. As far as I can tell, my truck was built with zero options, so I would guess the 3.73 rearend was standard. I actually like the setup. The 250 has good low-end torque, and pulls strong from a standing start with the 3-speed. Of course, top speed is somewhat limited, but unless you do a lot of freeway driving, it's really not a problem. I will also add that my gas mileage isn't that great for a 6-cylinder. I probably only get around 17 or 18 mpg. But I doubt that the guys running 350s get that kind of mileage. Also, my truck is a short-fleet bed, so it probably feels spunkier with this drivetrain than a LWB would. In this truck, this drivetrain seems more than adequate, and is a blast to drive. I'm not planning on changing the rearend, or any other part of the drivetrain. However, if it had posi-traction, that would be even better.



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