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Thread: GL-1 Gear Oil Alternative

  1. #1
    General mikew's Avatar
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    Default GL-1 Gear Oil Alternative

    I don't like GL-1 gear oil and wanted something "better" in my transfer case and transmission.

    GL-1 is hard to find, and finding one with a corrosion inhibitor is even harder!

    So I called my local HD truck driveline shop, Blumenthal's. They gave me the tech support phone number to Meritor, Rockwell's new name.

    I spoke with Meritor for awhile and this is what I learned.

    They recommend GL-1 with a corrosion inhibitor package, SAE 50W synthetic, or...

    SAE 30W, 40W or 50W motor oil that meets the CD spec.

    I asked, "You mean like 30W Rottella T diesel oil?" he said yep, you'll love it!

    Here's the lubrication document that covers all Meritor/Rockwell products and it includes T-136 transfer case info.

    We did not discuss the axels, but from this document they recommend a GL-5 lubricant for double reduction axles.

    If anyone knows the Rockwell axles part numbers for the Deuce I'd like to confirm they are listed as ones that use GL-5 before I switch.

    I'm off to Tractor Supply to get a 5 gal bucket of Rottella T to refill my transfer case that is sporting a brand new sprag in it!

    Mike W

  2. #2
    Colonel Snarky's Avatar
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    You can put what ever you want in the transfer case but the spicer transmissions and their yellow metal synchros get very angry if you don't put GL-1 in them, or something else that is yellow metal safe in them. The detergents and additives do unfortunate things to those pricey synchros, ask me how I know...
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  3. #3
    General mikew's Avatar
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    That's the thing, the transfer case has yellow metal syncros too. Meritor specifically warns not to use a GL-5 gear lube because it will eat yellow metal.

    Motor oil doesn't have the sulfur based additives that attack copper alloys but it does have lots of corrosion inhibitors.

    Many manual transmissions that have bronze syncros call for 30W motor oil.

    So what results did you have with motor oil in a Deuce transmission that went bad? What oil did you use?

    I'm feeling pretty darn safe about this, I'll report back with results.... in a few years!

    Mike W
    Last edited by mikew; 02-11-2010 at 18:54.

  4. #4
    4 Star General timntrucks's Avatar
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    i get GL-1 at the local napa store .. right off the shelf

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    4 Star General jesusgatos's Avatar
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    I'm running Amsoil fluids that are supposed to be compatible with yellow metals. No miles on Mah Deuce since I changed all the fluids though..
    no longer an active member on this forum

  7. #6
    3 Star General wdbtchr's Avatar
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    There is a thread on here from a couple of years ago n this very subject. There is a GL5 that is compatable with yellow metal, but I don't recall the details and don't have time to do a search for it right now.
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  8. #7
    Moderator WillWagner's Avatar
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    This has been covered many, MANY times. A search will yield oodles of hits. In a nutshell, read the label, if it is yellow metal compatable, you are good to go. IDK if i'd put 30wt motor oil in a vehicle that has the 26k capabilities, it might be a tad much for the lube.
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  9. #8
    2 Star General Jake0147's Avatar
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    MT-1 is the additional specification often tacked onto GL-5 that people say makes it backwards compatible. All I have ever found in that specification was specifically for non-synchronized boxes. Besides, if it were a backwards compatibility rating, why are certain GL-1 applications required to have GL-1 plus MT-1? It is inhibited a bit, but fully. I can't see filling my oil with stuff that my transmission can't make use of the benefits of, but is extremely susceptible to the side effects of, only to add more additives to counteract the additives I don't need... Oh well, who knows. I don't. I'll pose this question though, if more "improvers" are always better, what happened to GL-6?

    Napa has GL-1, usually in stock. That's what's called out in the TMs. Five gallon pails are the best value. 65-205 fits the TM recommendations, but it's dropped out of fancy for OTR trucks, it's not on the shelf there any more. The OEM recommendations from Spicer were for a 50 weight. If you're looking for a modernized upgrade to include R&O you can find that at the truck shops since (50W plus MT-1) in main stream use.
    Last edited by Jake0147; 02-11-2010 at 21:25.

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  11. #9
    General Westex's Avatar
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    They've run for decades with GL-1.
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    oldshep (12-31-2010)

  13. #10
    4 Star General glcaines's Avatar
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    I use GL-1 in mine and I found it available at all of the local autopart shops, but it was less expensive at NAPA.
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