12 bolt rear question - The 1947 - Present Chevrolet & GMC Truck Message Board Network

jhyder408 · 06-03-2013, 01:33 AM

so I bought this '67 long bed c10 for the bed and front clip. I am parting out the rest. I looked at the glove box door and the data plate said
posi-trac 4:11r. I jacked up the rear, marked the tire and marked the pinion. turned the tire one full revolution and the pinion spun a little past 4 turns. I inspected it, looks like it has never been out of the truck. I posted it on craigslist and had it sold in a bout a week. I went and pulled it out, which was a pain by the way, my theories of it never being out was correct by the way the u bolts being such a pain. Now to the point, the guy that bought it said when he got it home and checked it, said it was a 3:73 posi not 4:11.
This has been bothering me, I am not a scammer especially when selling parts. And I just think he is wrong.
SO, anybody have any thoughts on the matter???

**'68OrangeSunshine** · 06-03-2013, 05:45 AM

If you want to change the [GL-5] 90wt gear oil anyway, pull the pumpkin cover off the back of the diff and count teeth.
I think maybe the rearend was changed at some time anyway. I doubt if any one could tell an 18-year old differential job from a 40 year old one, given enough time, road muck and corrosion. If the nuts on the U-bolts are torqued correctly 120 foot-pounds -- they would be a bear to get off, anyway. Changing a rearend from 4.11 to 3.73 would be something a PO might do for better mileage.
Is it still a Posi? A lot of Posi rears get cannibalized for other projects, and if they blow up they are more expensive to replace or rebuild. Also the glovebox door with a SPID from a different truck may have found itself bolted onto the project at some point.
Or a PO used to a higher geared vehicle like a 3:08, might guess wrong about a lower-geared differential, without trying to be a liar.

cdowns · 06-03-2013, 06:21 AM

really both of your faults but mostly yours for takin responsibility for not checking to remove any doubt as to what u were selling
just guessin and hopeing aint really a good sales practice

me i would not have bought it without lookin cause i do not trust

06-03-2013, 01:33 AM	#1
jhyder408 Registered User Join Date: Oct 2007 Location: Albany, OR Posts: 93	12 bolt rear question so I bought this '67 long bed c10 for the bed and front clip. I am parting out the rest. I looked at the glove box door and the data plate said posi-trac 4:11r. I jacked up the rear, marked the tire and marked the pinion. turned the tire one full revolution and the pinion spun a little past 4 turns. I inspected it, looks like it has never been out of the truck. I posted it on craigslist and had it sold in a bout a week. I went and pulled it out, which was a pain by the way, my theories of it never being out was correct by the way the u bolts being such a pain. Now to the point, the guy that bought it said when he got it home and checked it, said it was a 3:73 posi not 4:11. This has been bothering me, I am not a scammer especially when selling parts. And I just think he is wrong. SO, anybody have any thoughts on the matter??? __________________ '68 C10 Step Side, 250 6cyl, converted long to short, work in progress

06-03-2013, 05:45 AM	#2
'68OrangeSunshine Senior Member Join Date: Feb 2002 Location: Tucson, AZ USA Posts: 7,504	Re: 12 bolt rear question If you want to change the [GL-5] 90wt gear oil anyway, pull the pumpkin cover off the back of the diff and count teeth. I think maybe the rearend was changed at some time anyway. I doubt if any one could tell an 18-year old differential job from a 40 year old one, given enough time, road muck and corrosion. If the nuts on the U-bolts are torqued correctly 120 foot-pounds -- they would be a bear to get off, anyway. Changing a rearend from 4.11 to 3.73 would be something a PO might do for better mileage. Is it still a Posi? A lot of Posi rears get cannibalized for other projects, and if they blow up they are more expensive to replace or rebuild. Also the glovebox door with a SPID from a different truck may have found itself bolted onto the project at some point. Or a PO used to a higher geared vehicle like a 3:08, might guess wrong about a lower-geared differential, without trying to be a liar. __________________ Every 25 years I like to rebuild that 292, whether it needs it or not.

06-03-2013, 06:21 AM	#3
cdowns Senior Member Join Date: Jan 2003 Location: daytonabeach Posts: 22,956	Re: 12 bolt rear question really both of your faults but mostly yours for takin responsibility for not checking to remove any doubt as to what u were selling just guessin and hopeing aint really a good sales practice me i would not have bought it without lookin cause i do not trust __________________ 71c-10 350/2004r/4:11 lowered3/4 longbed/dead by hurricane MEANING OF DEATH::::: SOMEBODY ELSE GETS YOUR STUFF DONT BELIEVE EVERYTHING YOU THINK TAKE MY ADVISE;I DON'T USE IT ANYWAY



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