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01-14-2015, 10:03 PM
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#1 |
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Senior Member
 
Join Date: Jan 2002
Location: Williston, ND
Posts: 2,999
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12 bolt help
Had my 12 bolt completely rebuilt. Ran great for 500-1000 miles. Then I decided to do a pretty massive burnout. The rear end started howling pretty bad after the burnout. What would be the most likely cause of the howling following a burnout?
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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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01-15-2015, 04:26 AM
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#2 |
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Senior Member
Join Date: Feb 2010
Location: Falls City, Nebraska "100 Miles From Nowhere"
Posts: 2,219
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Re: 12 bolt help
Supposed to change the oil at 500 miles (Break in period)...Did you follow the break in procedure? have you popped the cover and inspected the oil and gears? You may have burnt it up...Take it back to the shop.
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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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01-15-2015, 04:57 AM
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#3 |
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Senior Member
Join Date: Feb 2002
Location: Tucson, AZ USA
Posts: 7,248
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Re: 12 bolt help
If it was a Posi, did you use proper posi [ltd slip] gear oil: [GL-5] + anti-friction additive?
Usually bearings ''howl''. Just a lot of places with bearings in a differential. Broken axles go: "Craack!''
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Every 25 years I like to rebuild that 292, whether it needs it or not. |
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01-15-2015, 07:52 AM
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#4 | |
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Registered User
Join Date: May 2011
Location: Northern Calif.
Posts: 3,679
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Re: 12 bolt help
Quote:
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01-15-2015, 08:29 AM
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#5 |
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Registered User
Join Date: Dec 1999
Location: Austin, TX, USA
Posts: 7,717
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Re: 12 bolt help
Do you have positraction? Does it howl all the time or just while turning one direction?
If an open diff, you may have burned up spider gears. Pinion nut could have loosened changing gear engagment. Either pinon or carrier bearings could have overheated. Carrier bearings usuallly howl louder when turning, pinion all the time. Sounds like it has to come back apart...
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44 Willys MB 52 M38A1 64 Corvette Coupe 68 Camaro 'vert LT1 & TH700 69 Z/28 355 12.6's @110 69 Chevy Short Step 4 1/2"/7" drop 72 Jimmy 4WD 4spd 4" & 35's 02 GMC 2500HD 4x4 Duramax |
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01-15-2015, 09:00 AM
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#6 |
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Senior Member
Join Date: Jan 2002
Location: Williston, ND
Posts: 2,999
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Re: 12 bolt help
Its a posi and I followed break in instructions and had all the right fluids in it. Consensus seems to be pinion bearing...
__________________
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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01-15-2015, 09:03 AM
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#7 |
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Registered User
Join Date: Feb 2003
Location: Paragould, Ar
Posts: 571
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Re: 12 bolt help
I had a slight howl in my rearend the entire time I have had my truck. I had a posi installed this week and the mechanic checked and replaced a bad pinion bearing. The howl is gone. So that may be your issue.
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1970 Gmc Grande Sierra Swb 2wd LSX (LQ4/4L80e) 1990 K1500 Daily 
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01-15-2015, 09:54 AM
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#8 |
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Senior Member
Join Date: Jan 2002
Location: Williston, ND
Posts: 2,999
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Re: 12 bolt help
It howls at all times. I'm gonna have my guy look into the pinion bearing
__________________
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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01-15-2015, 10:20 AM
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#9 |
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Registered User
Join Date: Jun 2010
Location: Upland Ca
Posts: 4,143
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Re: 12 bolt help
I would not diagnos the problem for your mechanic. I would take it back and and simply say it started howling after a burn out, can you look at it?
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1972 C10 SWB, Air, PS, PB, 350/350THM. Second owner. 1965 Corvette roadster, 44K miles, 327/365 SHP, 4 speed, side exhaust, knockoffs, teak, second owner (bought in 1970), Have ALL numbers matching components. My frame off restoration thread: http://67-72chevytrucks.com/vboard/s...d.php?t=556703 |
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01-15-2015, 11:55 AM
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#10 |
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Senior Member
Join Date: Jan 2002
Location: Williston, ND
Posts: 2,999
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Re: 12 bolt help
I already took it out and he is just waiting to work on it
__________________
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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