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  1. #1
    Sr. Apprentice BlackHawk99's Avatar
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    Grand Blanc, MI
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    Default Limited slip differentials

    I am about the replace the leaky rear differential gasket on our 97 Tahoe. I have a new seal and 2 quarts of 80W90 gear lube. But, I'm not sure if this truck is a limited slip or not...and if it is, do I need the limited silp additive? If so, how much is necessary?

    Anyone know for sure? I want to make sure I do the job right.
    1997 Chevy Tahoe
    2002 GMC Sonoma
    2000 Pontiac Grand Prix GTP
    1999 Pontiac Firehawk
    1978 Pontiac Trans Am

  2. #2

    Default

    If you are reasonably sure it has the factory diff in there, look on your RPO code list for "G80": the RPO code for the factory "gov-lock" differential.

    Either way, though, the factory doesn't call for the LS additive for either the conventional open diff or the G80. The gov-lock is not a typical clutch type LS, so it doesn't need the additive that clutch type LS's call for.
    '98 K1500 Suburban LS 5.7 L 4L60E NV246 ARB
    '92 Ford Explorer XLT 4x4 4.0 L A4LD BW13-54 Trac-loc rear
    "My toys were the greasy cogs and springs and pistons that lay around all over the place, and these, I can promise you, were far more fun to play with than most of the plastic rubbish children are given nowadays." Danny in Roald Dahl's Danny The Champion of the World

  3. #3

    Default

    An easy way to tell if you need the additive is to jack up the rear end. With the transmission in park or in gear if it's a stick see if you can turn one wheel. If you have an open diff one wheel will turn forward and the other will turn the opposite way. If you have a posi then the axles will be locked together and the wheels will not turn.
    Jim

    2004 SILVERADO 2500HD LS
    Pro Comp Leveling Kit
    285-75-16 Cooper ST All Terrains
    Pro Comp Programmer
    Bilstein Shocks
    Linux Bed Liner
    Tinted Windows



    Other rides:

    1967 Landcruiser <350 Chevy>
    1970 Camaro
    1990 Geo Metro Convertible
    2007 FJ Cruiser

  4. #4

    Default

    Quote Originally Posted by Jimmiee View Post
    An easy way to tell if you need the additive is to jack up the rear end. With the transmission in park or in gear if it's a stick see if you can turn one wheel. If you have an open diff one wheel will turn forward and the other will turn the opposite way. If you have a posi then the axles will be locked together and the wheels will not turn.
    Except in the case of the G80. The G80 will behave just like an open diff: spin in opposite directions.
    '98 K1500 Suburban LS 5.7 L 4L60E NV246 ARB
    '92 Ford Explorer XLT 4x4 4.0 L A4LD BW13-54 Trac-loc rear
    "My toys were the greasy cogs and springs and pistons that lay around all over the place, and these, I can promise you, were far more fun to play with than most of the plastic rubbish children are given nowadays." Danny in Roald Dahl's Danny The Champion of the World

  5. #5

    Default

    Either Diff you possibility have does not call for the additive. You are going to need at least 1 more quart of gear lube.

    Differential, with 10.5 ring gear Dana Rear..........5.5 pints
    Differential, with 10.5 ring gear EX Dana Rear..........6.3 pints
    Differential, with 11 ring gear Dana Rear..........8.4 pints
    Differential, with 8.5, 8-5/8 ring gear Rear..........4.2 pints
    Differential, with 9.5 ring gear Rear..........5.5 pints
    Differential, with 9.75 ring gear Rear..........5.5 pints
    2008 GMC Sierra 2500HD Ex. Cab, Fire Red, 6.6L Duramax LMM Equipped with UTG Rocker Pods


    AMSOIL is the only oil company that...,"Recommends 25,000 mile oil changes","Gives up to four times better wear protection","Warranties your engine against oil related failure"

    Preferred Customers Save up to 30% Click here!!!
    Executive Direct Jobber ZO# 1695636
    Scott Douglass 248-721-1002
    Order online:
    www.1st-synthetics.com




  6. #6

    Default

    Quote Originally Posted by MrShorty View Post
    Except in the case of the G80. The G80 will behave just like an open diff: spin in opposite directions.
    Exactly! Even though it's a "posi" it doesn't require the additive because it is not locked in turns. The conventional Auburn style is always locked and will chatter in turns without the friction modifier.
    Jim

    2004 SILVERADO 2500HD LS
    Pro Comp Leveling Kit
    285-75-16 Cooper ST All Terrains
    Pro Comp Programmer
    Bilstein Shocks
    Linux Bed Liner
    Tinted Windows



    Other rides:

    1967 Landcruiser <350 Chevy>
    1970 Camaro
    1990 Geo Metro Convertible
    2007 FJ Cruiser

  7. #7
    Sr. Apprentice BlackHawk99's Avatar
    Join Date
    Apr 2009
    Location
    Grand Blanc, MI
    Posts
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    Default

    Thanks for the help, guys!

    I do have the G80 RPO code and have no reason to believe the rear end has ever been swapped out. But it sounds like I don't need the additive anyway.

    I'll pick up another quart of gear lube. AutoZone told me the capacity was 1.75 quarts. LOL That's what I get for listening to those guys! I'm going to tackle the job tomorrow night
    1997 Chevy Tahoe
    2002 GMC Sonoma
    2000 Pontiac Grand Prix GTP
    1999 Pontiac Firehawk
    1978 Pontiac Trans Am

  8. #8
    Sr. Apprentice BlackHawk99's Avatar
    Join Date
    Apr 2009
    Location
    Grand Blanc, MI
    Posts
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    Default

    I swapped out the gasket. What an act of congress it was to get the 10 bolts off! 12 years of rust really made things a challenge.

    So...got it all swapped and drove it about 50 miles. The leak is back. I'm so irritated. UGH. I wire wheeled the cover and removed all the gasket residual from the mating surface on the rear diff. Set the new gasket in place with RTV on both sides. Cleaned the bolts with a wire wheel and used PB Blaster on them before torquing them down. I torqued them to 165 inch lbs (13.75 ft. lbs.). Did I do something wrong? This feels like a waste of what should have been a really easy job.
    1997 Chevy Tahoe
    2002 GMC Sonoma
    2000 Pontiac Grand Prix GTP
    1999 Pontiac Firehawk
    1978 Pontiac Trans Am

  9. #9

    Default

    Are you certain the leak is through the gasket? A lot of times other seals (especially a leaky pinion seal) will look like a leaky gasket because the oil flows down the housing and drips off the bottom: right where the gasket seal would drip.

    I've had trouble sealing up a diff before because I used the wrong "stuff". Don't take offense, but are you certain you used RTV silicone? There's another product out there that calls itself a "gasket maker" but isn't RTV, and it doesn't work on gear oil.

    All sealing surfaces looked clean without imperfections/scratches/pitting/etc.? Housing flat? Cover flat and not bent?
    '98 K1500 Suburban LS 5.7 L 4L60E NV246 ARB
    '92 Ford Explorer XLT 4x4 4.0 L A4LD BW13-54 Trac-loc rear
    "My toys were the greasy cogs and springs and pistons that lay around all over the place, and these, I can promise you, were far more fun to play with than most of the plastic rubbish children are given nowadays." Danny in Roald Dahl's Danny The Champion of the World

  10. #10

    Default

    I swapped out the gasket. What an act of congress it was to get the 10 bolts off! 12 years of rust really made things a challenge.

    So...got it all swapped and drove it about 50 miles. The leak is back. I'm so irritated. UGH. I wire wheeled the cover and removed all the gasket residual from the mating surface on the rear diff. Set the new gasket in place with RTV on both sides. Cleaned the bolts with a wire wheel and used PB Blaster on them before torquing them down. I torqued them to 165 inch lbs (13.75 ft. lbs.). Did I do something wrong? This feels like a waste of what should have been a really easy job.

    Did you use a synthetic gear lube? You can not use RTV with synthetic lubricants. They react and cause seal failure.
    2008 GMC Sierra 2500HD Ex. Cab, Fire Red, 6.6L Duramax LMM Equipped with UTG Rocker Pods


    AMSOIL is the only oil company that...,"Recommends 25,000 mile oil changes","Gives up to four times better wear protection","Warranties your engine against oil related failure"

    Preferred Customers Save up to 30% Click here!!!
    Executive Direct Jobber ZO# 1695636
    Scott Douglass 248-721-1002
    Order online:
    www.1st-synthetics.com




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