12 bolt limited slip posi, is it factory? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

bucky_21_7 · 02-23-2008, 08:04 AM

So over the summer i jacked up my rear end to see if I had a posi without taking off the rear end cover. I spun the wheels and they spun in the opisit direction.So seeing that i presumed i had no posi, just peg leg. Today I pulled off the cover and found a limited slip posi ( not the clutch posi, the spring one) sitining in there. Now the question is, is the limited slip factory? The rear end gears are 3.08's. I read unless stated on the options list that factory atomatic trucks are 3.08 gears and 3 and 4 speeds are 3.73 gears. Am I right? My truck was a factory atomatic truck so the gears are right but is the limited slip? There is no indication on the option list of it. If not where did it come from? Thanks

**special-K** · 02-23-2008, 09:39 AM

It may be factory,but if it was original to the truck the option would be listed.

dave2953 · 02-23-2008, 11:12 AM

My truck is an automatic too, but it has 3.73's. The trans. was special order (Powerglide), so I'm not sure if that has anything to do with it or not.

dazza · 02-23-2008, 12:13 PM

I just recently replaced my gasket and cleaned things up. I don't know about the automatic, but mine's a manual and it came from the factory with a 3.07 posi. There should be an axle code stamped on top of the axle, passenger side. This thread has a picture and a link to decode it:
http://67-72chevytrucks.com/vboard/s...ight=axle+code

That should tell you what you have, unless of course somebody has changed it out.

What year is your truck?

dazza · 02-23-2008, 12:17 PM

Here's the recent cleanup ...

Longhorn Man · 02-23-2008, 12:29 PM

4 speeds got 3.07 as did hydromatic trucks... I think the glide got 3.73, but I'm not certian.

skokie · 02-23-2008, 12:31 PM

What did you use to clean it up and paint it?

dazza · 02-23-2008, 12:48 PM

I was actually surprised at the lack of rust (very little) on the front side of the diff. I guess the 1/2 inch of oil and road grime was a good protectant! I sanded the cover and used a degreasing gel on the rest. Used brake cleaner on the inside. Primered and sprayed.

Longhorn Man · 02-23-2008, 01:06 PM

Quote:

Originally Posted by ETsC10

I'm a little confused here too.
I have 3.73 and the spid just indicates a posi and T400:

04G80AB POSITRACT AXLE
04M49CG TURBO HYDRA-MATIC

The trucks bone stock, trany and rearend wise...

And here's the answer...
in 68, the option listing for M49 (TH400... since there was no Th350 yet);
Turbo Hydramatic; includes HD radiator, includes 3.07 rear axle gear when ordered with 327 or 396 engine.
So, your truck was either a 250, 292, or a 307 powered truck originally.

I made it ALMOST all day without learning anything... you ruined it for me!

bucky_21_7 · 02-24-2008, 01:10 AM

My truck is a 72

dazza · 02-24-2008, 01:21 AM

So get a flashlight and a wire brush and take a look on the top part of the axle tube, passenger side of the differential, should be a stamped code. Post them here and I'll decode, or go here:

http://www.americanclassic.com/paint_test.asp

2nd_wnd · 02-24-2008, 03:54 AM

my 72 gmc has a factory limited slip with 350 and th 350 tranny. all listed on the spid. i'll get a pic.

Ooops I was wrong its factory posi.

dazza · 02-24-2008, 04:35 AM

I believe posi or limited slip is the same thing.

Funny how the spid listings can differ, mine doesn't show the rear ratio.

What the hell is G78-15-8 HIGHWAY B8 ??

dave2953 · 02-24-2008, 04:42 AM

I believe that's referring to the tires that came factory, which were bias ply.

CG · 02-24-2008, 06:19 AM

On my 71 4x4 it says it has a G86 no spin rear axle on the spid. Whats the difference between that and a posi, or is it the same thing?

bucky_21_7 · 02-24-2008, 09:07 PM

k i'll check that code out on mon

LONGHAIR · 02-24-2008, 10:57 PM

Quote:

On my 71 4x4 it says it has a G86 no spin rear axle on the spid. Whats the difference between that and a posi, or is it the same thing?

"No-Spin" is Detriot locker.

Quote:

Funny how the spid listings can differ, mine doesn't show the rear ratio.

dazza, that just means that yours has the "standard" gear...not optional

Quote:

I believe posi or limited slip is the same thing.

Yes, "posi-traction" is GM's "trademark" word for limited slip. It has become part of regular speech though, like Kleenex, Xerox, etc.

CG · 02-24-2008, 11:59 PM

Thanks for that info LONGHAIR now I have to look that up and see what it is =) It makes a clunk now and then back there.

02-23-2008, 08:04 AM	#1
bucky_21_7 Registered User Join Date: May 2007 Location: Winnipeg Manitoba Posts: 59	12 bolt limited slip posi, is it factory? So over the summer i jacked up my rear end to see if I had a posi without taking off the rear end cover. I spun the wheels and they spun in the opisit direction.So seeing that i presumed i had no posi, just peg leg. Today I pulled off the cover and found a limited slip posi ( not the clutch posi, the spring one) sitining in there. Now the question is, is the limited slip factory? The rear end gears are 3.08's. I read unless stated on the options list that factory atomatic trucks are 3.08 gears and 3 and 4 speeds are 3.73 gears. Am I right? My truck was a factory atomatic truck so the gears are right but is the limited slip? There is no indication on the option list of it. If not where did it come from? Thanks

02-23-2008, 09:39 AM	#2
special-K Special Order Join Date: Nov 2004 Location: Mt Airy, MD Posts: 85,859	Re: 12 bolt limited slip posi, is it factory? It may be factory,but if it was original to the truck the option would be listed. __________________ "BUILDING A BETTER WAY TO SERVE THE USA"......67/72......"The New Breed" GMC '67 C1500 Wideside Super Custom SWB: 327/M22/3.42 posi.........."The '67" (project) GMC '72 K2500 Wideside Sierra Custom Camper: 350/TH350/4.10 Power-Lok..."The '72" (rolling) Tim "Don't call me a redneck. I'm a rough cut country gentleman" R.I.P. ~ East Side Low Life ~ El Jay ~ 72BLUZ ~ Fasteddie69 ~ Ron586 ~ 67ChevyRedneck ~ Grumpy Old Man ~

02-23-2008, 11:12 AM	#3
dave2953 Dave's not here, man Join Date: Jun 2004 Location: Winder, Georgia Posts: 2,000	Re: 12 bolt limited slip posi, is it factory? My truck is an automatic too, but it has 3.73's. The trans. was special order (Powerglide), so I'm not sure if that has anything to do with it or not. __________________ - 2014 VW Jetta - 2015 VW Jetta - 1966 Ford F-250 Last edited by dave2953; 02-24-2008 at 04:38 AM.

02-23-2008, 12:13 PM	#4
dazza Registered User Join Date: Aug 2002 Location: California Posts: 971	Re: 12 bolt limited slip posi, is it factory? I just recently replaced my gasket and cleaned things up. I don't know about the automatic, but mine's a manual and it came from the factory with a 3.07 posi. There should be an axle code stamped on top of the axle, passenger side. This thread has a picture and a link to decode it: http://67-72chevytrucks.com/vboard/s...ight=axle+code That should tell you what you have, unless of course somebody has changed it out. What year is your truck? __________________ --------------------------------------------------------- I'm not crazy, I'm chosen, there's a difference. ---------------------------- '72 K10 SWB, 350, sm465/np205 ---- ----

02-23-2008, 12:17 PM	#5
dazza Registered User Join Date: Aug 2002 Location: California Posts: 971	Re: 12 bolt limited slip posi, is it factory? Here's the recent cleanup ... Attached Images __________________ --------------------------------------------------------- I'm not crazy, I'm chosen, there's a difference. ---------------------------- '72 K10 SWB, 350, sm465/np205 ---- ----

02-23-2008, 12:29 PM	#6
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,693	Re: 12 bolt limited slip posi, is it factory? 4 speeds got 3.07 as did hydromatic trucks... I think the glide got 3.73, but I'm not certian.

02-23-2008, 12:31 PM	#7
skokie Registered User Join Date: Oct 2003 Location: San Jose Ca. Posts: 3,334	Re: 12 bolt limited slip posi, is it factory? What did you use to clean it up and paint it? __________________ RIP to my son Dylan. 5/17/2002 - 8/18/2018 If you want to know more about rare forms of pediatric cancer or if you want to help fund pediatric cancer research, please check out the website for the non-profit I started. https://slothforpedcancer.org 68 build thread http://67-72chevytrucks.com/vboard/s...d.php?t=223234

02-23-2008, 12:48 PM	#8
dazza Registered User Join Date: Aug 2002 Location: California Posts: 971	Re: 12 bolt limited slip posi, is it factory? I was actually surprised at the lack of rust (very little) on the front side of the diff. I guess the 1/2 inch of oil and road grime was a good protectant! I sanded the cover and used a degreasing gel on the rest. Used brake cleaner on the inside. Primered and sprayed. __________________ --------------------------------------------------------- I'm not crazy, I'm chosen, there's a difference. ---------------------------- '72 K10 SWB, 350, sm465/np205 ---- ----

02-24-2008, 01:10 AM	#10
bucky_21_7 Registered User Join Date: May 2007 Location: Winnipeg Manitoba Posts: 59	Re: 12 bolt limited slip posi, is it factory? My truck is a 72

02-24-2008, 01:21 AM	#11
dazza Registered User Join Date: Aug 2002 Location: California Posts: 971	Re: 12 bolt limited slip posi, is it factory? So get a flashlight and a wire brush and take a look on the top part of the axle tube, passenger side of the differential, should be a stamped code. Post them here and I'll decode, or go here: http://www.americanclassic.com/paint_test.asp __________________ --------------------------------------------------------- I'm not crazy, I'm chosen, there's a difference. ---------------------------- '72 K10 SWB, 350, sm465/np205 ---- ----

02-24-2008, 03:54 AM	#12
2nd_wnd Registered User Join Date: Feb 2007 Location: Winston Salem, NC Posts: 310	Re: 12 bolt limited slip posi, is it factory? my 72 gmc has a factory limited slip with 350 and th 350 tranny. all listed on the spid. i'll get a pic. Ooops I was wrong its factory posi. __________________ 72 LWB Last edited by 2nd_wnd; 02-24-2008 at 04:02 AM. Reason: added photo

02-24-2008, 04:35 AM	#13
dazza Registered User Join Date: Aug 2002 Location: California Posts: 971	Re: 12 bolt limited slip posi, is it factory? I believe posi or limited slip is the same thing. Funny how the spid listings can differ, mine doesn't show the rear ratio. What the hell is G78-15-8 HIGHWAY B8 ?? __________________ --------------------------------------------------------- I'm not crazy, I'm chosen, there's a difference. ---------------------------- '72 K10 SWB, 350, sm465/np205 ---- ----

02-24-2008, 04:42 AM	#14
dave2953 Dave's not here, man Join Date: Jun 2004 Location: Winder, Georgia Posts: 2,000	Re: 12 bolt limited slip posi, is it factory? I believe that's referring to the tires that came factory, which were bias ply. __________________ - 2014 VW Jetta - 2015 VW Jetta - 1966 Ford F-250

02-24-2008, 06:19 AM	#15
CG BlahBlahBlah Join Date: Feb 2002 Location: Wa. Posts: 19,862	Re: 12 bolt limited slip posi, is it factory? On my 71 4x4 it says it has a G86 no spin rear axle on the spid. Whats the difference between that and a posi, or is it the same thing? Last edited by CG; 02-24-2008 at 06:20 AM.

02-24-2008, 09:07 PM	#16
bucky_21_7 Registered User Join Date: May 2007 Location: Winnipeg Manitoba Posts: 59	Re: 12 bolt limited slip posi, is it factory? k i'll check that code out on mon



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02-24-2008, 11:59 PM	#18
CG BlahBlahBlah Join Date: Feb 2002 Location: Wa. Posts: 19,862	Re: 12 bolt limited slip posi, is it factory? Thanks for that info LONGHAIR now I have to look that up and see what it is =) It makes a clunk now and then back there.

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