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Synthetic gear oil in diffs

Discussion in 'GM Powertrain' started by Ralph S, Jan 30, 2011.

  1. Ralph S

    Ralph S New Member

    Has anyone switched to full synthetic gear oil in the diffs in an older truck? I heard that lot of the older trucks, mine is a 99 Suburban, can't have synthetic gear oil because it deteriorates the seals. I guess it was the RTV used in them that doesn't work well with additives in full synth.
  2. tbplus10

    tbplus10 Epic Member Staff Member 5+ Years 5000 Posts Platinum Contributor

    Synthetic is slipperier than petroleum lubes, it doesnt deteriorate the seals it just gets passed older seals easier.
    Leaks when going to a synthetic lube isnt a guarrantee, I've had some leak while others hold just fine.
  3. phoebeisis

    phoebeisis Epic Member 5+ Years 1000 Posts

    I put syn lube-Mobil 1 75w90 I think-in my 1998 Suburban when I got it 4 years and 21,000 miles ago. It has 215,300 miles now- no problems.

    I'm a mpg nut, so I use syn whenever possible-cheap insurance also since it is supposed to last a bit longer(usually), and I might forget to change at the proper interval(same story with syn oil- it idiots proofs it to some extent- me being the idiot who might forget to change it).

    Charlie
  4. silveradotrailblazer

    silveradotrailblazer Epic Member 5+ Years ROTM Winner 5000 Posts

    I use Mobil 1 Synthetic in my '96 Burb since new, no problems.
  5. Ralph S

    Ralph S New Member

    Cool. Thanks for your help all.

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