71 swb posi rear end problems - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Brently · 04-08-2004, 07:44 AM

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

JimKshortstep4x4 · 04-08-2004, 08:24 AM

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

**smitty62** · 04-08-2004, 09:22 AM

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!

HuggerCST · 04-08-2004, 10:23 AM

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.

Brently · 04-08-2004, 12:51 PM

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

**Classic Heartbeat** · 04-08-2004, 01:06 PM

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

HuggerCST · 04-08-2004, 01:58 PM

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)

I think I just confused myself.

You can get posi additive at NAPA, part #SL-2411. Made by Siloo.

Sweet72 · 04-08-2004, 02:38 PM

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.

Brently · 04-08-2004, 02:42 PM

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

JimKshortstep4x4 · 04-08-2004, 10:10 PM

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

04-08-2004, 07:44 AM	#1
Brently Registered User Join Date: Feb 2002 Location: Chattanooga Posts: 151	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

04-08-2004, 09:22 AM	#3
smitty62 Registered User Join Date: May 2002 Location: North Carolina Posts: 1,234	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! __________________ Stepsides look like real trucks! Smitty

04-08-2004, 10:23 AM	#4
HuggerCST Registered User Join Date: Jul 2001 Location: North Louisiana Posts: 4,501	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. __________________ 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

04-08-2004, 12:51 PM	#5
Brently Registered User Join Date: Feb 2002 Location: Chattanooga Posts: 151	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

04-08-2004, 01:06 PM	#6
Classic Heartbeat Project Junkie! Fishing Poor!! Join Date: Dec 1999 Location: Olympia,Wa. 98512 Posts: 10,770	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 __________________ On-line catolog Classic Heartbeat Pickup Parts WEHEPP@comcast.net Call us Toll Free (888) 338-2502 Like Us on Facebook No appointment necessary. 72 BB Chevy Custom Deluxe / Custom Camper 67 I-6 (Soon to be 5.7 LS1) Panel 68 BB Chevy Short Bed 72 6.0 LQ9 Short Bed Chevy 4X4 Olympia's fastest growing truck parts supplier. Olympia's home for Wayward Chevys

04-08-2004, 08:24 AM	#2
JimKshortstep4x4 Senior Member Join Date: Jul 2001 Location: Muskegon,MI,USA Posts: 6,026	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

04-08-2004, 01:58 PM	#7
HuggerCST Registered User Join Date: Jul 2001 Location: North Louisiana Posts: 4,501	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) I think I just confused myself. You can get posi additive at NAPA, part #SL-2411. Made by Siloo. __________________ 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

04-08-2004, 02:38 PM	#8
Sweet72 Registered User Join Date: Nov 2003 Location: Alexandria, VA Posts: 1,534	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. __________________ '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.

04-08-2004, 02:42 PM	#9
Brently Registered User Join Date: Feb 2002 Location: Chattanooga Posts: 151	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

04-08-2004, 10:10 PM	#10
JimKshortstep4x4 Senior Member Join Date: Jul 2001 Location: Muskegon,MI,USA Posts: 6,026	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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