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#1 |
Registered User
Join Date: Feb 2002
Location: Chattanooga
Posts: 151
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71 swb posi rear end problems
i have a popping in the rear end when i slow down and turn - one explained it like i was hopping over a brick - a hard pop but only happens when i slow way down to turn - i have been on here before and it was suggested to change the fluid in the rear end before doing anything else - my questions now are what type of exact fluid do i need to use - is there anything that needs to be added because it is a posi rear end? also how do i identify the exact gear ratio of a rear end - i am rear end ignorant - thanks, Brent
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#2 |
Senior Member
Join Date: Jul 2001
Location: Muskegon,MI,USA
Posts: 6,026
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Posi's will make noise sometimes and it is more or less normal.
There are a couple of ways to go on the lube. You can change the lube out and fill with regular 90 wt. gear lube. Additives are available, either GM or aftermarket and it should be added. The other way is to buy gear lube with the additive in it. If you change the lube, you can check the ratio out as it will be stamped on the ring gear, (You will have to pull the cover to change the lube). Another possibility is to check the present lube and if nice and clean, just add the additive. Jim |
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#3 |
Registered User
![]() Join Date: May 2002
Location: North Carolina
Posts: 1,234
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After you change fluid and add the additive, go to an empty parking lot and make several small circles clockwise and then the same counter-clockwise. It works!
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#4 |
Registered User
Join Date: Jul 2001
Location: North Louisiana
Posts: 4,501
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The posi-additive will more than likely fix the popping sound. To determine what gear ratio you have, divide the number of teeth on the ring gear by the number of teeth on the pinion gear. These numbers are usually stamped on the ring gear.
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Wynne 70 CST short fleet Hugger orange & white, 350/350, ps, pb, air, tilt, tach/vac/speedwarning, original buckets, AM/FM, oak bed floor, shoulder belts, 3.5"/5.5" drop, 20" American Racing VN425s. Build thread 53 Chevy shortbed 69 Camaro Click here to subscribe Chevy GMC International Truck Club Louisiana Charter Member http://www.louisianaclassictruckclub.com |
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#5 |
Registered User
Join Date: Feb 2002
Location: Chattanooga
Posts: 151
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rear end
can this fluid and additive be found at a parts store? - also i am guessing it is a posi - again not real familiar with rear ends but the glove box calls for a posi and the truck is original so i don't think it has been changed - how to tell? thanks, Brent
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#6 |
Project Junkie! Fishing Poor!!
![]() Join Date: Dec 1999
Location: Olympia,Wa. 98512
Posts: 10,770
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It sounds like you have a possi to me. If you want to check it, just jack the rear end up and spin one wheel. If they both turn in the same direction, then you have a possi. The additive can be purchased at any parts store also. WES www.ClassicHeartbeat.com
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#7 |
Registered User
Join Date: Jul 2001
Location: North Louisiana
Posts: 4,501
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Wes is right, with a good posi, both wheels should turn the same direction, (trans in neutral) but keep in mind that if the clutches are worn out, and you turn one wheel, the other wheel may not turn. If you have a single trac, the other wheel will definately turn in the opposite direction. But, if yours is popping, your clutches are probably good.(Unless something is broken)
![]() ![]() ![]() You can get posi additive at NAPA, part #SL-2411. Made by Siloo.
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Wynne 70 CST short fleet Hugger orange & white, 350/350, ps, pb, air, tilt, tach/vac/speedwarning, original buckets, AM/FM, oak bed floor, shoulder belts, 3.5"/5.5" drop, 20" American Racing VN425s. Build thread 53 Chevy shortbed 69 Camaro Click here to subscribe Chevy GMC International Truck Club Louisiana Charter Member http://www.louisianaclassictruckclub.com |
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#8 |
Registered User
Join Date: Nov 2003
Location: Alexandria, VA
Posts: 1,534
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Man, I installed all new clutches when mine was popping in low speed turns. I tried changing gear oil w/additive, no joy. The new clutches and oil cured the problem though.
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'72 GMC SWB C1500 Custom, frame-off in progress. 383 SBC, 9:1CR, Comp Cams XE262H, Scat internal balanced crank, Eagle SIR 6" rods, Keith Black dish pistons, Dart Iron Eagle 72/180 heads, Weiand Stealth intake, Stewart stage I water pump, Holley 4bbl vac sec, TH350 with B&M Shift Improver Kit. 12 bolt positraction. ![]() ![]() ![]() |
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#9 |
Registered User
Join Date: Feb 2002
Location: Chattanooga
Posts: 151
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rear end
if i have to do so i may be calling on you for help - is this something i can do myself or will i have to have it done if need be? how expensive to do myself if i can and how expensive if someone else does it? Thanks, Brent
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#10 |
Senior Member
Join Date: Jul 2001
Location: Muskegon,MI,USA
Posts: 6,026
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As WES suggested check out the rear end to make sure it is a posi, if it is, change the fluid and add the additive.
If the clutches are worn, they are available. I would suggest buying a service manual as it will be very helpful. Jim |
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