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#1 |
Senior Member
![]() Join Date: Feb 2009
Location: Northern Nevada
Posts: 7,242
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How do you know if you have positraction?
71 Chevy 1/2 ton short with 12-bolt rear-end. I have no reason to believe it's been rebuilt. I've seen positraction on a SPID before, but it's not on mine. I know nothing about rear ends (no pun intended), but this one has high gears. Doesn't much even burn the tires until it chirps when the transmission hits second gear.
My SPID is below, not that it necessarily matters: ![]()
__________________
Tony 71 Custom Deluxe, SWB, 2WD, 402, A/C. I developed an assembly kit for restoring the (a) truck from the ground up. My build thread, and more on the assembly kit https://67-72chevytrucks.com/vboard/...d.php?t=730025 |
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#2 | |
Account Suspended
Join Date: Jan 2007
Location: Tucson
Posts: 2,183
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Re: How do you know if you have positraction?
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#3 |
Senior Member
Join Date: Jan 2003
Location: daytonabeach
Posts: 22,956
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Re: How do you know if you have positraction?
you could take the rear cover off and drain the 45year old fluid out and start with freash clean good stuff that way you can look at the gears too
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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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#4 |
Senior Member
![]() Join Date: Jan 2002
Location: Williston, ND
Posts: 2,999
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Re: How do you know if you have positraction?
I agree, if you believe it still has the original fluid, open it up and change it out. Look at gears and post pics if you are unsure if its a posi. You will find some numbers on the gears, for example 41:10 which means 4.10 gears. Divide first number by second. Get yourself some good gear fluid and a new gasket and you'll be set to check your rearend out
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68 Chevy CST/10, 50th Anniversary, 327/th400, 373 posi, buckets 68 GMC Shortbox Stepside, 402/th400, Tilt, Tach, Bucket Seats, 3.08 Positraction 69 Chevy Camaro SS, 383, 4 speed, positraction 70 Chevy El Camino SS396, Triple Black, 454/th400, Tach 70 Chevy Shortbox Stepside 4x4, 350/th350, Tilt, Tach, Cab Lights, Bumper Guards, Tow Hooks 70 Chevy 3/4 Longbox, 350/auto, 70k, SURVIVOR 71 Chevy Blazer, CST, 350/auto 71 GMC Sierra K2500, 454, 4 speed, 4.10 posi, 37s 71 Custom/30, Open Road, 350/th400, tilt 72 Chevy Shortbox Fleetside, 496 Stroker/th400, Tilt, Tach, Bucket Seats, 3.42 Posi 72 GMC Sierra Grande 2500. 427/th400, tilt, a/c, tool and stowage, buckets/console, 3.54 posi |
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#5 |
20' Daredevil (Ret)
![]() Join Date: May 2003
Location: Jefferson State
Posts: 13,640
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Re: How do you know if you have positraction?
Always a good thing to have fresh fluid. Just to check for posi, jack up the rear enough to raise both tires off the ground.... parking brake off and trans in neutral. Rotate either rear tire by hand. If the opposite side tire rotates in the opposite direction it's an open diff. If it rotates in the same direction it's a posi.
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- Mike - 1972 K20 LWB 350/350/205 RIP El Jay |
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#6 |
Senior Member
![]() Join Date: Jan 2001
Location: Orem, Utah
Posts: 7,915
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Re: How do you know if you have positraction?
The absolute best way and a nice favor to do for that rear gear that's been working so hard for all these years. Just be aware that if it is a posi, you'll either need to add friction modifier to the fresh gear oil or use a synthetic rated for posi (I put Royal Purple in mine - it doesn't require a modifier).
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#7 |
Senior Member
![]() Join Date: Feb 2009
Location: Northern Nevada
Posts: 7,242
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Re: How do you know if you have positraction?
Ha!..............The fluid has been changed before, but I've always paid to have it done. I'll be doing this in the future. Not certain what to look for, but if I haven't figured it out by then, then I'll take a picture.
Apparently one way is to lift the rear end, emergency brake off, and put it in neutral. Spin one tire clockwise. If the other tire spins counterclockwise, then it's not positraction.
__________________
Tony 71 Custom Deluxe, SWB, 2WD, 402, A/C. I developed an assembly kit for restoring the (a) truck from the ground up. My build thread, and more on the assembly kit https://67-72chevytrucks.com/vboard/...d.php?t=730025 Last edited by 71CHEVYSHORTBED402; 11-02-2015 at 01:11 AM. |
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#8 |
20' Daredevil (Ret)
![]() Join Date: May 2003
Location: Jefferson State
Posts: 13,640
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Re: How do you know if you have positraction?
Yeah, I've heard that somewhere before...
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- Mike - 1972 K20 LWB 350/350/205 RIP El Jay |
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#9 |
Special Order
![]() ![]() Join Date: Nov 2004
Location: Mt Airy, MD
Posts: 85,859
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Re: How do you know if you have positraction?
Keeping fluid changed is the best prevention for rear end failure. But, we can only assume yours is one that wasn't ever changed. Some trucks out there may have had the fluid changed every 10k like clockwork. For a simple way to answer a simple question, do as Fitz said and put the tires on grass or dirt and see if one or two wheels spin.
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"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 ~ |
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#10 |
Senior Member
Join Date: Jul 2004
Location: Round Rock, Texas
Posts: 858
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Re: How do you know if you have positraction?
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Hook'em |
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#11 |
Registered User
Join Date: Aug 2015
Location: Waco Kentucky
Posts: 35
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Re: How do you know if you have positraction?
Jack both rear wheels off of the ground, turn wheel by hand,if both wheels turn same direction,its posi.You can also get a close idea of gear ratio at this time by marking driveshaft and wheel and counting revolutions of driveshaft to each turn of the wheel.
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#12 |
Registered User
Join Date: Sep 2015
Location: Lake Placid florida
Posts: 599
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Re: How do you know if you have positraction?
Since this has been answered, hopefully nobody will think I'm hijacking the tread. When I jack mine up and turn one wheel, the other does not turn at all. What does that mean?
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#13 |
Registered User
![]() Join Date: Feb 2014
Location: West Iowa
Posts: 1,106
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Re: How do you know if you have positraction?
It means your posi is wore out, out of tune, or you don't have a posi. This is why sometimes jacking up or peeling out doesn't work(when the posi clutches are wore out or out of adjustment). Bruce
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#14 |
Senior Member
![]() Join Date: Feb 2009
Location: Northern Nevada
Posts: 7,242
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Re: How do you know if you have positraction?
You sure it was in neutral?
__________________
Tony 71 Custom Deluxe, SWB, 2WD, 402, A/C. I developed an assembly kit for restoring the (a) truck from the ground up. My build thread, and more on the assembly kit https://67-72chevytrucks.com/vboard/...d.php?t=730025 |
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#15 |
Registered User
Join Date: Sep 2015
Location: Lake Placid florida
Posts: 599
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Re: How do you know if you have positraction?
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#16 |
Senior Member
![]() Join Date: Feb 2009
Location: Northern Nevada
Posts: 7,242
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Re: How do you know if you have positraction?
Thanks
__________________
Tony 71 Custom Deluxe, SWB, 2WD, 402, A/C. I developed an assembly kit for restoring the (a) truck from the ground up. My build thread, and more on the assembly kit https://67-72chevytrucks.com/vboard/...d.php?t=730025 |
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#17 |
Senior Member
![]() Join Date: Feb 2009
Location: Northern Nevada
Posts: 7,242
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Re: How do you know if you have positraction?
How about options D through E?: "You don't have posi, the rear end is out of tune or wore out"
__________________
Tony 71 Custom Deluxe, SWB, 2WD, 402, A/C. I developed an assembly kit for restoring the (a) truck from the ground up. My build thread, and more on the assembly kit https://67-72chevytrucks.com/vboard/...d.php?t=730025 Last edited by 71CHEVYSHORTBED402; 11-06-2015 at 12:24 AM. |
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#18 |
Senior Member
![]() Join Date: Feb 2010
Location: Falls City, Nebraska "100 Miles From Nowhere"
Posts: 2,219
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Re: How do you know if you have positraction?
A Posi has springs like this,
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Michael of the clan Hill, "Two Seventy Two's" 71 1-ton Dually 350 4-Speed 71 C/50 Grain Truck, 350 Split-Axle 4-Speed 02 3/4 ton Express 14 Indian Chief Vintage 1952 Ford 8N, "Only Ford Allowed On The Property" ![]() "Be American, Buy American" ![]() |
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#19 | |
Senior Member
![]() Join Date: Feb 2009
Location: Northern Nevada
Posts: 7,242
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Re: How do you know if you have positraction?
Quote:
__________________
Tony 71 Custom Deluxe, SWB, 2WD, 402, A/C. I developed an assembly kit for restoring the (a) truck from the ground up. My build thread, and more on the assembly kit https://67-72chevytrucks.com/vboard/...d.php?t=730025 |
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#20 |
Senior Member
![]() Join Date: Nov 2008
Location: Cleveland, OH
Posts: 591
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Re: How do you know if you have positraction?
I doubt we need anyone else chiming in, but I will anyway. I have a couple vehicles with limited slip/posi units and the jacking the car up and spinning the tires with the trans in neutral doesn't really work. In theory yes, but anything with a little age won't respond correctly.
Both vehicles will lay a furious yard or two with both tires, but won't spin in the same direction when jacked up and put in neutral. Pulling the cover is the sure bet or doing a burnout! |
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#21 |
Senior Member
![]() Join Date: Feb 2009
Location: Northern Nevada
Posts: 7,242
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Re: How do you know if you have positraction?
Makes sense 10.
One reason I asked is I got a smoking deal on a red posi tag. Very curious, does anyone know what the correct posi tag is for the 71? I've seen red tags that mount with the filler plug (I suspect not right due to plug on my truck) and a metal tag mounted with a cover bolt.
__________________
Tony 71 Custom Deluxe, SWB, 2WD, 402, A/C. I developed an assembly kit for restoring the (a) truck from the ground up. My build thread, and more on the assembly kit https://67-72chevytrucks.com/vboard/...d.php?t=730025 |
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#22 |
Registered User
![]() Join Date: May 2014
Location: PA
Posts: 1,417
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Re: How do you know if you have positraction?
I see Fitz is suspended again LMAO
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1967 C10, LWB, 250, Powerglide, PS, PB, 3/4 STATIC DROP |
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#23 |
Senior Member
![]() Join Date: Feb 2009
Location: Northern Nevada
Posts: 7,242
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Re: How do you know if you have positraction?
Does anyone know what the correct posi tag is for the 71? I've seen red tags that mount with the filler plug (I suspect not right due to plug on my truck) and a metal tag mounted with a cover bolt.
__________________
Tony 71 Custom Deluxe, SWB, 2WD, 402, A/C. I developed an assembly kit for restoring the (a) truck from the ground up. My build thread, and more on the assembly kit https://67-72chevytrucks.com/vboard/...d.php?t=730025 |
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#24 | |
Senior Member
![]() Join Date: Feb 2010
Location: Falls City, Nebraska "100 Miles From Nowhere"
Posts: 2,219
|
Re: How do you know if you have positraction?
Quote:
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__________________
Michael of the clan Hill, "Two Seventy Two's" 71 1-ton Dually 350 4-Speed 71 C/50 Grain Truck, 350 Split-Axle 4-Speed 02 3/4 ton Express 14 Indian Chief Vintage 1952 Ford 8N, "Only Ford Allowed On The Property" ![]() "Be American, Buy American" ![]() Last edited by Ironangel; 11-21-2015 at 12:48 AM. |
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#25 |
Senior Member
![]() Join Date: Feb 2009
Location: Northern Nevada
Posts: 7,242
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Re: How do you know if you have positraction?
Here are the tags I was referring to. I don't know which is correct for a 1971, but I suspect it's the first one:
One goes on the cover http://www.ebay.com/itm/64-72-Chevel...hVQWM8&vxp=mtr Two goes with the plug: https://s3.amazonaws.com/gearbox-yea...es/j/ja902.png Three goes with the plug also: http://chevelle.com/media/extendware...on-tag-ce1.jpg Yes two and three differ. You may miss it at first.
__________________
Tony 71 Custom Deluxe, SWB, 2WD, 402, A/C. I developed an assembly kit for restoring the (a) truck from the ground up. My build thread, and more on the assembly kit https://67-72chevytrucks.com/vboard/...d.php?t=730025 Last edited by 71CHEVYSHORTBED402; 11-21-2015 at 01:41 AM. |
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