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  1. #1

    Default Synthetic gear oil in diffs

    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. #2


    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. #3

    Join Date
    Jun 2006
    River Ridge Louisiana-4 miles W of New Orleans-didn't flood-water stopped 800 yards away.


    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).

    1998 suburban-
    1/2 ton

    199500 miles

  4. #4


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

  5. #5


    Cool. Thanks for your help all.

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